Good calories, bad calories by gary taubes; new york: aa knopf

Good Calories, Bad Calories by Gary Taubes;
New York: AA Knopf

Pennington Biomedical Research Center, Baton Rouge, LA, USA Good Calories, Bad Calories has much useful information and is well worthreading. Gary Taubes's tenets related to obesity can be summarized in four Received 11 February 2008; accepted 14 statements (i) He believes that you can gain weight and become obese without a February 2008 positive energy balance; (ii) He also believes that dietary fat is unimportant for thedevelopment of obesity; (iii) Carbohydrate, in his view, is what produces obesity Address for correspondence: GA Bray, and (iv) Insulin secreted by the carbohydrate is the problem in obesity. However, Pennington Center, 6400 Perkins Road, Baton some of the conclusions that the author reaches are not consistent with current Rouge, LA 70808, USA. E-mail: concepts about obesity. There are many kinds of obesity, and only some depend on diet composition. Two dietary manipulations produce obesity in susceptiblepeople: eating a high-fat diet and drinking sugar- or high-fructose corn syrup-sweetened beverages. Insulin is necessary but not sufficient in the diet-dependentobesities. When diet is important, it may be the combination of fat and fructose(the deadly duo) that is most important. Regardless of diet, it is a positive energybalance over months to years that is the sine qua non for obesity. Obese peopleclearly eat more than do lean ones, and food-intake records are notoriouslyunreliable, as documented by use of doubly labelled water. Underreporting of foodintake is greater in obese than in normal-weight people and is worse for fat thanfor other macronutrient groups. Accepting the concept that obesity results froma positive energy balance does not tell us why energy balance is positive. Thisdepends on a variety of environmental factors interacting with the genetic sus-ceptibility of certain individuals. Weight loss is related to adherence to the diet,not to its macronutrient composition.
Keywords: Diet, energy expenditure, food intake, nutritian.
obesity reviews (2008) 9, 251–263
our cities, they have probably introduced to us the whole Diseases of modern society and the
train of nervous disorders, and increased the frequency of corpulence.
Wadd, W. 1810 (2) I believe no age did ever afford more instances of corpu-lency than our own.
Some factor of diet and/or lifestyle must be driving Short, T. 1727 (1) weight upward, because human biology and our under- If the increase of wealth and the refinement of modern lying genetic code cannot change in such a short time.
times have tended to banish plague and pestilence from Taubes, G. 2007 (3) 2008 The Author Journal compilation 2008 The International Association for the Study of Obesity. obesity reviews 9, 251–263
Good Calories, Bad Calories book review and critique G. A. Bray favour of the carbohydrate-insulin hypothesis. The bibliog- Industrialization of food production raphy is robust and contains a wealth of information. The The quotes by Short (1) in the early 18th century and by page notes provide detailed references to the sources. It is Wadd (2) from the early 19th century indicate that obesity well worth reading. The descriptions of important scientific has been a growing problem for more than two centuries.
contributions are well written.
The current rise in the rate of increase serves to make The book begins with Mr William Banting and the diet solutions to the problem more urgent. Clearly genetic and he published in 1863 as a small pamphlet called ‘A Letter environmental factors such as the food we eat, the relative on Corpulence Addressed to the Public' (6). In this pam- affiuence of individuals, and the predisposing genetic basis phlet, Banting described his dietary success with a low- upon which these factors act in each of us play a role in the carbohydrate diet. The hostility that Mr Banting aroused obesity problem.
among the ‘medical establishment' in the 1860s is reminis- Many revolutions characterize the changing human diet.
cent of some of the comments about popular diets that have The first of these revolutions began with the domestication come from the ‘medical establishment' in the last half of of animals and cultivation of crops more than 10 000 years the 20th century. Throughout Good Calories, Bad Calo- ago (1). As rice, wheat and corn became staple commodi- ries, there are historical vignettes about the men and ties, hunter-gatherers abandoned their migratory life and women who made the discoveries. The calorie-restriction gradually turned to the cultivation of plants to provide studies of Benedict and the studies by Ancel Keys et al. (7) food for the human species, which supported the develop- published in The Biology of Human Starvation are well ment of nation states.
worth reading. Having lived through and testified before Sugar first appeared some 2500 years ago, probably in the Senate Select Committee on Nutrition in the 1970s, I India, and spread slowly throughout the world. With the found it fascinating to see an analysis of the impact of this discovery of the New World at the end of the 15th century, political approach to dietary advice for Americans and the the sugar industry blossomed to provide a major source of Dietary Guidelines that followed. The description of the caloric sweeteners (4).
Pima Indians and their history during the 20th century are The industrial revolution of the 18th century had a major well done. The background work on energy expenditure impact on agriculture and food production. With machine in human beings from Antoine Lavoisier, Hermann Helm- farming, processing and storage of crops, and the use of holtz, Robert Mayer Carl Voit, Max Pettenkoffer, Max chemical fertilizers, human beings were able to move from Rubner and Wilbur Atwater is very nicely detailed by Mr farms to cities. At the beginning of the 20th century, Taubes. In addition to these, there are many other descrip- farming provided a major need for human labour, but as tions of scientists and their work that make this book the century progressed, we moved to the point where only particularly fascinating to read.
a small percentage of the population working on the land Good Calories, Bad Calories is divided into three main could provide food for the city dwellers.
parts. The first part is a critique of the Diet-Heart hypoth- As nations became wealthier in the 20th century, one esis, and the idea that dietary fat was the principal culprit society after another entered a nutrition transition, shifting in the rising incidence of heart disease during the 20th dietary intake from simple unprocessed foods to highly century. From an analysis of published data and discussion processed foods with larger quantities of meats, added with many leaders, Taubes concludes that the Diet-Heart sugars, fats, and sweetened foods (5). Although it occurred hypothesis detracted from our understanding of the rela- in Western countries during the 19th century and early part tion of diet to heart disease. As Taubes sees it, Ancel Keys of the 20th century, it has been the reduced burden of played the role of major villain in selling the idea that infectious disease and the ‘Westernization' of diets around dietary fat was the major contributor to the increased risk the world that have led to the rapidly rising incidence of of heart disease. Read and decide for yourself.
heart disease, obesity, diabetes, and cancer. This ‘nutrition The second part of Good Calories, Bad Calories sets transition' has brought with it all of the chronic diseases forth the ‘carbohydrate hypothesis'. This hypothesis is that afflict Western society (5). The impact of diet on Taubes's basis for explaining the evils of the ‘nutrition disease is the subject of Good Calories, Bad Calories by transition' that have afflicted countries moving from their Gary Taubes (3).
traditional diets to the Western type of high-fat, high-sugar,high-salt diet. The carbohydrate hypothesis is described indetail in this section and is related to the increasing devel-opment of diabetes, cancer, ageing and dementia.
Summary of Good Calories, Bad Calories
In the third part of Good Calories, Bad Calories, called Good Calories, Bad Calories is a scholarly book that the ‘Mythology of Obesity', the author argues that the musters the evidence for the case against the high-fat energy-balance equation does not adequately explain hypothesis for heart disease, cancer and obesity and in obesity because obese people do not eat more than lean 2008 The Author Journal compilation 2008 The International Association for the Study of Obesity. obesity reviews 9, 251–263
Good Calories, Bad Calories book review and critique G. A. Bray ones, and because they can lose weight eating a large end of the summer, one of the girls, who lived only a short number of calories, provided that the calories are very low distance from the hospital, wanted to come back to see us in carbohydrates – that is, high in protein and fat.
so she could continue to lose weight. We instructed her on It is clear, as the author says, that ‘Some factor of diet how to keep a food diary. When she returned 2 weeks later, and/or lifestyle must be driving weight upward, because she had gained a few pounds. She showed us her diary, human biology and our underlying genetic code cannot which was very neatly and carefully kept. The average daily change in such a short time. The standard explanation is food intake was about 300–400 kcal d-1. As she had lost that in the 1970s we began consuming more calories than weight eating 1000 kcal d-1 while directly observed in the we expended and so as a society we began getting fatter, hospital, we were sceptical of the accuracy of her outpa- and this tendency has been particularly exacerbated since tient recording. We instructed her again on keeping food the early 1980s. Data from the US Department of Agricul- records. She returned after another 2 weeks, having gained ture as well as those from the National Center for Health even more weight and with records still showing she only Statistics show that the rise in food intake has been in ate 300 kcal d-1 or so. There was an obvious discrepancy, the range of 150–350 kcal d-1 in the last 30 years. These reflecting the difficulty of keeping reliable records. It was increased calories would more than account for the obesity thus clear that this girl was either kidding herself or trying to kid us about how much she was eating. We have subse- As I read through Good Calories, Bad Calories, I found quently had the opportunity to study weight loss in a a number of errors of omission or commission that are number of subjects in both the metabolic unit and then on important when relating diet to disease. There is no similar diets in an outpatient setting. Weight loss under observation is about 50% faster than with the equivalent lipoprotein-cholesterol (‘bad cholesterol') or of high- ‘prescribed' energy deficit in an outpatient setting (8). The density lipoprotein-cholesterol (‘good cholesterol'). The difference is adherence to or compliance with the diet.
cholesterol receptor, the discovery of which earned Brown Let me make my position very clear. Obesity is the and Goldstein the Nobel Prize, is not mentioned, nor are result of a prolonged small positive energy surplus with the statin drugs that arose from this discovery. The statin fat storage as the result. An energy deficit produces weight class of drugs has been very important in reducing the loss and tips the balance in the opposite direction from deaths from heart disease. Also absent is any mention of trans-fats, which, along with saturated fats in animal and The Law of Conservation of Mass and Energy (9) (the dairy products, are the dietary fats most predictive of heart first law of thermodynamics) applies to humans as it does to other species. Over the period of about 100 years from In the section on ‘The Mythology of Obesity' and the 1787 to 1896, the Laws of Conservation of Matter and carbohydrate-insulin hypothesis, there is no mention of Energy were shown to apply to human beings, just as they doubly labelled water, a sophisticated technique that has do to animals.
allowed us to ‘check' on the accuracy of self-reports of food From my reading of Good Calories, Bad Calories, the intake. Also missing is a discussion of the ‘nutrient' balance author seems to misinterpret what this relationship means.
hypothesis. These limitations may change the conclusions The thermodynamic laws relate overall changes. They are that are reached from reading Good Calories, Bad so-called ‘state' equations. That is, they tell us what happens to the system under the specified conditions The final section of this book summarizes the lessons that (dieting or overeating). They do not tell us how the change the author learned. They are reproduced in the left-hand occurred (composition of the diet or type of activity). I see column of Table 1. I have added my comments in the nothing inconsistent with the truth of the idea that a posi- right-hand column.
tive energy balance produces obesity and the idea that itdoes not tell us why this imbalance occurred.
Leptin is an important hormone produced by adipose Critique of Good Calories, Bad Calories
tissue. When it is deficient, massive obesity from overeatingis the result (10). Treatment with leptin will reverse this Positive energy balance causes obesity: calories type of obesity. Before we knew that leptin existed or how do count – food-intake records are unreliable – a leptin worked, the positive energy balance that occurs in its absence still occurred, with the resulting obesity. The Law One summer I admitted a group of four overweight teen- of Conservation of Mass and Energy still applies.
agers to our clinical research unit at the Harbor UCLA The challenge to those of us working in the field of Medical Center and put them on a 1000-cal diet under obesity research is to identify those factors that produce the direct observation. As expected, all of the girls lost weight small increases in energy intake or the small decreases in and were delighted with the result. When they left at the energy expenditure in a way that will produce the long- 2008 The Author
Journal compilation 2008 The International Association for the Study of Obesity. obesity reviews 9, 251–263
Good Calories, Bad Calories book review and critique G. A. Bray Table 1 The author's ten conclusions from Good Calories, Bad Calories and my comments
Author's comments 1 Dietary fat, whether saturated or not, is not a cause of obesity, heart Dietary fat produces obesity in mice, rats, dogs and human beings. On disease, or any other chronic disease of civilization.
a low-fat diet, the type of solid carbohydrate in the diet does not 2 The problem is the carbohydrates in the diet, their effect on insulin The problem is a positive energy balance persisting over an extended secretion, and thus the hormonal regulation of homeostasis – the period of time, which may be exacerbated by high-fructose/high-fat entire harmonic ensemble of the human body. The more easily foods and other environmental agents acting on genetically digestible and refined the carbohydrates, the greater the effect on our health, weight and well-being.
3 Sugars – sucrose and high-fructose corn syrup (HFCS) – are Fructose – found both in sucrose and HFCS – is mainly metabolized in particularly harmful, probably because the combination of fructose the liver; glucose (also in HFCS and sugar) is distributed throughout and glucose simultaneously elevates insulin levels while overloading the body. The effects of fructose in the liver may be particularly the liver with carbohydrates.
4 Through their direct effect on insulin and blood sugar, refined There is no convincing evidence that carbohydrates are producing carbohydrates, starches and sugars are the dietary cause of cancer, Alzheimer's disease, type 2 diabetes, or coronary artery coronary heart disease anddiabetes. They are the most likely dietary causes of cancer, Alzheimer's disease, and the other chronic diseases of civilization.
5 Obesity is a disorder of excess fat accumulation, not overeating, Obesity is the result of a small positive energy balance occurring over and not sedentary behaviour.
time. The Laws of Conservation of Energy (First Law of Thermodynamics) do not tell us why this imbalance occurs.
6 Consuming excess calories does not cause us to grow fatter any Consuming excess calories routinely produces obesity, and consuming more than it causes a child to grow taller. Expending more energy fewer calories than your body needs produces weight loss.
than we consume does not lead to long-term weight loss; it leads to 7 Fattening and obesity are caused by an imbalance – a Fat accumulation cannot occur without caloric intake exceeding disequilibrium – in the hormonal regulation of adipose tissue and fat expenditure. Fat deposits differ in their health risks: visceral fat is metabolism. Fat synthesis and storage exceed the mobilization of strongly related to heart disease and diabetes; subcutaneous fat from the adipose tissue and its subsequent oxidation. We abdominal fat much less so; and fat on the legs may be ‘protective'.
become leaner when the hormonal regulation of the fat tissue These differences in fat locations partly determine the differences in reverses this balance.
life expectancy between men and women.
8 Insulin is the primary regulator of fat storage. When insulin levels Insulin is needed for fat storage, but it is for the purpose of storing the are elevated – either chronically or after a meal – we accumulate fat ‘extra' calories not needed for daily energy expenditure. Chronic in our fat tissue. When insulin levels fall, we release fat from our fat elevation of insulin, as in insulinoma, has only a modest effect on tissue and use it for fuel.
weight – something else is needed for ‘obesity' in addition to insulin.
9 By stimulating insulin secretion, carbohydrates make us fat and Calories count. Fructose (HFCS or sugar) plus a modest- or high-fat ultimately cause obesity. The fewer carbohydrates we consume, the diet enhance the risk of overpowering the homeostatic feedback leaner we will be.
10 By driving fat accumulation, carbohydrates also increase hunger The quantity of fat we eat in a day is less than 0.5% of the fat we have anddecrease the amount of energy we expend in metabolism and stored, and these changes in fat deposition do not lead to increased physical activity.
appetite, as they are hardly seen on the concentration of leptin and other adipose tissue-related peptides.
term imbalance that we call obesity. It is what the Law of Lean people adjust energy intake or energy expenditure Conservation of Mass and Energy does not tell us that is over an extended period of time better than people who most important when it comes to dealing with the public become obese do. In classic experiments on this problem, health aspects of obesity. This law does not explain bio- Edholm et al. (12) (omitted from the bibliography of logical differences in food intake or in the regulation of fat Good Calories Bad Calories) showed that the daily intake distribution. The hedonic effects of food are not explained of food was not significantly related to energy expendi- by this Law, and it contains no information about how ture on that day. Only over a period of several days were prices of food influence food choices. The first Law also food intake and energy expenditure significantly related.
does not help us to understand genetic influences, which we This longer term adaptation is critical for understanding know account for a significant amount of the susceptibility the mechanism(s) that allow some people to maintain to obesity (11). It is ‘environmental' agents, such as tasty, body weight while others fail to do so (13). The quota- inexpensive food in large portion sizes, inactivity, viruses, tion from Boswell cited in Good Calories, Bad Calories toxins, and social interactions, that interact with the geneti- clearly summarizes the idea of positive caloric balance as cally susceptible host to produce obesity.
the cause of obesity: 2008 The Author Journal compilation 2008 The International Association for the Study of Obesity. obesity reviews 9, 251–263
Good Calories, Bad Calories book review and critique G. A. Bray Talking to a man who was growing very fat, so as to be to appear, it was compared with the information from food incommoded with corpulence; records. The data showed that normal-weight peopleunderreport what they eat by 10–30%. This means that Johnson said, He eats too much sir dietary food-intake records underestimate energy expendi- Boswell: ‘I don't know, Sir; you see one man fat who eats ture by nearly a quarter. For overweight people, the degree moderately, and another lean who eats a great deal- of underreporting is higher, varying from 30% to 50%.
Johnson: ‘Nay, Sir, whatever may be the quantity that a Thus, food records as a measure of ‘real' calorie need are man eats, it is plain that if he is too fat, he has eaten more unreliable, as for any individual you do not know how than he should have done'.
much he or she actually underreports. Moreover, underre- porting seems to be higher for dietary fat (18). When food-intake records are used, the greater discrepancy reported bythe obese would make their data closer to those of normal- Energy expenditure and food-intake records weight people who underreport less. The data on energy Obesity has been a fact of human existence as far back as requirements based on doubly labelled water measure- the Old Stone Age (15). The extent to which any given ments from many laboratories were compiled in the Rec- instance of obesity is dependent on diet, and to what ommended Dietary Intakes (19), one of the sources that are extent, vary from one individual to another. The fact that not cited in Good Calories, Bad Calories. Table 2 compiles obesity has occurred in every culture would indicate that some of these data. The body mass index (BMI) is 5–7 units some individuals in each culture are ‘susceptible'. Individu- higher in the overweight group than in the normal-weight als identified with obesity through the ages are much more group and the overweight men expend 300–500 calories likely to come from the wealthy and aristocratic members more per day than do the normal-weight men, meaning of that society than from the peasants and labourers. This that they must eat more food just to maintain their weight.
implies an interaction between environmental factors and The women are even heavier, with a 6- to 10-unit BMI difference and energy expenditures that are 100–500 In developing his ideas about calories and obesity in calories more per day. To maintain this extra weight the Good Calories, Bad Calories, Taubes argues that obese women have to eat enough food to provide this extra individuals do not eat more than lean ones do. The data for his belief come from the Diet and Health Report (16) In Good Calories, Bad Calories, Taubes says that ‘All prepared by the National Academy of Sciences. This report those who have insisted (and still do) that overeating said ‘Most studies comparing normal and overweight and/or sedentary behaviour must be the cause of obesity people suggest that those who are overweight eat fewer have done so on the basis of this same fundamental error: calories than those of normal weight'. Further on, the they will observe correctly that positive caloric balance author says ‘Even if it could be established that all obese must be associated with weight gain, but then they will individuals eat more than do the lean – which they don't – assume without justification that positive calorie balance that only tells us that eating more is associated with being is the cause of weight gain. This simple misconception has obese'. As a member of the committee drafting the Diet and led to a century of misguided obesity research'. Again, the Health Report, I was responsible for writing this section.
author has repeated his misunderstanding of the Law of The data used in this report were based on food-intake Conservation of Mass and Energy. When we heat a closed records and reflected the information of the day. Even then, vessel and note that the temperature and pressure rise, that however, there was a paradox. Measurements of energy is what the Laws of Thermodynamics predict will happen.
expenditure using oxygen consumption showed a nearly It is irrelevant whether the heat is chemical or electrical.
linear increase in energy expenditure as body weight Experiments in which human subjects voluntarily overeat increased. This meant that heavier people were expending (20,21) provide the link between calorie intake and calories more energy than were leaner ones. How did the over- going into body fat stores. The weight and fat gains that weight people keep up their higher energy expenditure if follow conscious overeating in human subjects are a clear they did not ingest more food? test of the cause-and-effect relation of the energy-balance We now know that the data used in the Diet and Health concept. The author of Good Calories, Bad Calories seems Report were wrong and that obese people eat more food to miss this point. The concept of energy imbalance as the energy than do lean ones. The answer to this apparent basis for understanding obesity at one level does not pre- paradox came from a new technique for measuring total clude any of the influences that affect or modify food intake daily energy expenditure (17). This technique allows us to or energy expenditure, including the quantity and quality measure total energy expenditure over an interval of of food, toxins, genes, viruses, sleeping time, breast feeding, 7–10 days and cannot be influenced by the subjects' food medications, etc. They are just the processes that modify intake. As information obtained from this technique began one or other component of the energy-balance system.
2008 The Author
Journal compilation 2008 The International Association for the Study of Obesity. obesity reviews 9, 251–263
Good Calories, Bad Calories book review and critique G. A. Bray Table 2 Total daily energy expenditure for
normal-weight and overweight males and females using doubly labeled water* Mean total energy Mean total energy expenditure (kcal d-1) expenditure (kcal d-1) *Adapted from the Recommended Dietary Intakes (19).
This scientific journey through the limitations of food- starches and flours which man uses as the base for his intake records and the new framework for interpreting daily nourishment . . A double cause of obesity results food intake by using doubly labelled water has been nicely from too much sleep combined with too little exer- captured in the quotes from Canguilhem (22) and from cise . . The final cause of obesity is excess, whether in Sarton (23). Our progress involves curves and bumps in the eating or drinking.
Brillat-Savarin on the treatment of obesity: The history of truth is neither linear nor monotone.
Any cure of obesity must begin with the three following Canguilhem, G (22) and absolute precepts: discretion in eating, moderation When we say that science is essentially progressive this in sleeping, and exercise on foot or on horseback'. ‘Such does not mean that in his quest for truth man follows are the first commandments which science makes to us: always the shortest path. Far from it, he beats about the nevertheless I place little faith in them.
bush, does not find what he is looking for but finds Brillat-Savarin JA 1826 (25) something else, retraces his steps, loses himself in variousdetours, and finally after many wanderings touches thegoal.
Diet and weight gain Weight gain independent of diet In science, you test hypotheses by examining their predic- Regulation of body weight gain can be viewed as a homeo- tions. Producing positive energy balance by asking human static system. The word ‘homeostasis' was introduced into subjects to eat extra food has routinely produced fat gain biology nearly a century ago by the great American Physi- (20,21). Similarly, inducing energy deficit by asking human ologist, Walter B. Cannon (26). It describes the overall way beings to exercise more or by restricting food intake has in which the body adapts to internal and external infor- routinely produced fat and weight loss (24). If the author of mation to remain on an ‘even keel'. During the year, the Good Calories, Bad Calories wishes to challenge these ‘average' man will ingest nearly 1 million calories, and the fundamental controlled experiments, he needs to provide average woman will eat nearly 750 000 calories. A weight data showing that they are wrong.
gain of 0.5 kg (1.1 lb) during the year represents the Brillat-Savarin, who is discussed in Good Calories, Bad storage of about 3500 calories, or less than a 0.5% error.
Calories, has very nice quotes that summarize the issues The homeostatic system that we call ‘weight regulation' has related to the causes of obesity and its treatment (25).
worked pretty well over this year, as an error of 0.5% is Brillat-Savarin on the causes of obesity: small, and for most people the weight gain may be even The first is the natural temperament of the individual smaller, meaning the operation of this homeostatic system . . The second principal cause of obesity lies in the is functioning quite well.
2008 The Author Journal compilation 2008 The International Association for the Study of Obesity. obesity reviews 9, 251–263
Good Calories, Bad Calories book review and critique G. A. Bray Under some circumstances, however, the system fails – We have learned a lot about obesity during the 20th that is, weight is not maintained this precisely, and we century. One of the recurring themes during this time was gain 0.5–2 kg year-1 (1.1–4.4 lb year-1). With the wide the idea that people could consume extra calories and variety of ‘tasty' and energy-packed foods that we can ‘burn' them up. The term for this, coined by German inves- eat, I view this as a problem of a pleasurable or hedonic tigators, is ‘luxuskonsumption' – dissipation of calories environment overriding our homeostatic system. That is, when we overeat. Although this idea has raged up and for some people who are susceptible to obesity, in an down, most scientists no longer believe it. Part of this environment where there are pleasurable rewards from conclusion comes from a careful reanalysis of the data food, the homeostatic system is not able to maintain body originally thought to support luxuskonsumption. In the weight. Two important hedonic factors are dietary fat and discussion of luxuskonsumption in Good Calories, Bad dietary fructose [from sugar or high-fructose corn syrup Calories, the author fails to note the reanalysis by Gilbert (HFCS)], which together make what I would call the Forbes (28) of the data published by Gulick (29) and by ‘deadly duo' (4).
Neumann (30) in the early 20th century. Neumann and This homeostatic system can also be disturbed by a Gulick each conducted experiments on themselves. They number of environmental agents. Some of the medications varied the amount of food they ate and recorded their we use can either lower or raise body weight over extended weights. Each claimed that the changes in their body weight periods of time by ‘resetting' the homeostatic system. One did not reflect the amount of food they ate. When Forbes example is nicotine in tobacco. In human beings and re-plotted their small weight changes against their actual animals, this drug reduces food intake and stimulates calorie intake the lines were linear and could account for energy expenditure. Individuals who smoke weigh less on essentially all of the extra calories consumed.
average than those who do not. The weight gain that occurs Obesity is not a single entity and many different ways when smoking stops is a significant problem. A second have been described to produce and classify it. One of the example are the antipsychotic drugs. Several of the second leaders in the field of obesity during the latter part of the generation of antipsychotic drugs (e.g. olanzepine and cloz- 19th century was von Noorden (31), who identified three epine) produce significant weight gain and increase the risk types of obesity (i) diabetogenous obesity; (ii) endogenous for diabetes. A final example is from the drugs intended obesity and (iii) exogenous obesity. He noted that obesity primarily for weight loss. Rimonabant is a cannabinoid and diabetes were related. This relationship is particularly antagonist that produces weight loss. When individuals clear in the Pima Indians and other South-western Indian were randomly switched back to placebo after 1 year of Tribes. Pima Indians have one of the highest rates of dia- treatment with this drug, their rate of weight regain was betes in the world. The BMI of Pima Indians living in almost the mirror image of their weight loss during the first southern Arizona, where fat and fructose (from beverages) year. Those who stayed on the drug for 2 years maintained are readily available, is several units higher than their close their weight loss. In each case, we have adjusted the homeo- relatives living a more ‘primitive' life in northern Mexico, static system by changing the gain. If you turn down a radio demonstrating again the importance of the ‘Western' diet in and other noise occurs in the background, the radio will the fattening of America (32).
not make more noise. It has been reset. The problem for von Noorden's two other types of obesity – endogenous most treatments of obesity is that they do not reset the and exogenous – correspond to what I will call diet- system at a sufficiently low level.
independent and diet-dependent (33). At one extreme are In Good Calories, Bad Calories, the author says ‘Some the types of obesity that develop independent of diet com- factor of diet and/or lifestyle must be driving weight position. At the other extreme are those where diet com- upward, because human biology and our underlying position plays a major role. The most obvious examples genetic code cannot change in such a short time. The stan- of obesities that are independent of diet composition are dard explanation is that in the 1970s we began consuming those resulting from single-gene defects and neuroendo- more calories than we expended and so as a society we crine disorders. Children with leptin deficiency are very began getting fatter, and this tendency has been particularly obese (10). Individuals who lack leptin receptors or who exacerbated since the early 1980s'. The detrimental impact fail to produce pro-opiomelanocortin or have abnormali- of the Western diet on health is easy to see all around us. It ties in the melanocortin-4 receptor provide other clear-cut is also easily demonstrated in epidemiologic studies. Indi- examples of genetic disturbances where the drive to eat is viduals moving from Japan to Hawaii or to the USA (27) overwhelming. The type of diet is irrelevant to these types shift their dietary and disease patterns towards those in the of obesity. The affected individuals will eat just about USA. Immigrants from Europe show the same shift. To put this into the context of the homeostatic model, the Western A second group of obesities where diet is secondary are diet has provided a hedonic override for their homeostatic those associated with neuroendocrine diseases, including system of weight regulation and disease prevention.
hypothalamic obesity, Cushing's syndrome and polycystic 2008 The Author
Journal compilation 2008 The International Association for the Study of Obesity. obesity reviews 9, 251–263
Good Calories, Bad Calories book review and critique G. A. Bray ovary syndrome (33). Injury to the ventromedial hypo- liver and then transport them to the fat for storage. This thalamus produces a disturbance in the control of food important difference in metabolism and the fact that the intake and in control of the autonomic nervous system.
metabolic products of fatty acids cannot be converted back These animals are very hyperphagic, but this hyperphagia is to glucose put glucose in a very special position. We gen- not necessary for them to become obese. Increased activity erally eat each day about as much carbohydrate as we can of the parasympathetic nervous system and decreased activ- store. As storage capacity is limited, dietary carbohydrate ity of the sympathetic nervous system combine to increase must be metabolized. In contrast, the amount of fat we eat insulin levels and allow these animals to shift nutrients each day is well under 1% of the fat we have stored in our from metabolism and growth into storage as body fat (34).
bodies, even those with a normal body weight. Thus, main-taining fat balance and carbohydrate balance is an integral Diet-dependent obesity: high-fat diets product obesity – part of the concept of energy balance that is at the heart of high-carbohydrate diets with low fat do not At the other extreme are the types of obesity in animals and There seems to be a lower limit to the amount of dietary human beings that depend on the composition of the diet.
fat that is essential for animals to become obese. Once this The two principal dietary components are fat and fructose.
level is surpassed, carbohydrate may well enhance the In the theme line of Good Calories, Bad Calories, the obesity. There is one dose–response study (37) to various author argues that dietary fat is not important in the devel- levels of fat. There was a rapid increase in body fat as opment of obesity. For example, he says, ‘But there is no dietary fat increased from 20% to 40%, with an inflection evidence linking obesity to dietary fat consumption – point between 30% and 40% fat. Below 20% fat, it is neither between populations nor in the same population'.
difficult to become obese. This would be consistent with the Yet, in the bibliography, there is a reference titled ‘Dietary lack of obesity among Japanese eating their traditional very fat affects obesity rate' published in the American Journal low-fat, high-starch diet.
of Clinical Nutrition by Bray and Popkin (35), which out-lines precisely these data, both between populations and Fat balance – the flatt hypothesis within populations. High-fat diets consistently produce Why is a high-fat diet conducive to the development of obesity in mice, rats and dogs. Without regard for the data, obesity? First, fat has a higher energy density than do other the author says, ‘But some strains of rats, perhaps most of foods. Second, metabolic adaptation to a high-fat diet them, will not grow obese on high-fat diets, and even those requires a longer time than to a high-carbohydrate diet that do will grow fatter on a high-fat, high-carbohydrate (38,39). To put the problem in perspective, we need a brief diet than a high-fat, low-carbohydrate diet'. Among detour into the way the body handles fat and glucose.
rodents, it is the exception that does not become obese to Glucose can be converted into fat, and this happens rela- some extent while eating a high-fat diet. It is also true that tively easily in small animals, but in human beings there is the magnitude of obesity varies from eating a high-fat diet.
very limited conversion of glucose carbons into the carbons Mixing fat with sweet-tasting carbohydrates (fructose of long-chain fatty acids. In contrast, fatty acid carbons alone or in sugar or HFCS) will accentuate the weight gain.
cannot be converted back into net glucose by either rodents Weight loss with high-fat diets has been examined in at least two meta-analyses (35,36). In one study, a reduction To explore the concept of ‘nutrient balance', a concept of 10% in the proportion of energy from fat was associated that is not discussed in Good Calories, Bad Calories, Flatt with a reduction in weight of 16 g d-1, which translates into measured the oxidation of dietary glucose and fat in mice a 1.4- to 2.8-kg weight loss over 3–6 months (35). In a housed individually (40). He found that there were varia- second meta-analysis of 12 intervention trials, the reduc- tions in glucose and fat use from day to day in individual tion in fat intake was 10.2%(95% CI 8.1–12.3%). The animals. If more glucose was used than eaten on 1 day, the low-fat intervention groups showed a greater weight loss animal would make a correction and eat more glucose the than did control groups (3.2 kg 95% CI 1.9–4.5) Astrup next day. These corrective responses were much less evident et al. (36) found a weighted mean change of energy intake for fat. For energy balance to occur, we must also be in fat of 1138 kJ d-1 (about 275 kcal d-1). Having a body weight balance. As glucose stores are limited, reductions in dietary 10 kg higher than the average pretreatment body weight sources of glucose will reduce the utilization of glucose and was associated with a 2.6-kg greater difference in favour fat. In his studies, Flatt showed that animals eat weight loss. Thus, reducing dietary fat is associated with for carbohydrate and that when carbohydrate in the diet is significant weight reduction over 3–12 months.
limited, which is what happens with a high-fat diet, one Rodents have a marked capacity for synthesis of fatty response is to expand fat stores until the rate of fat oxida- acids in adipose tissue, where they can then be stored. In tion increases to match the fat in the diet. This is why contrast, human beings produce very few fatty acids in the high-fat diets are a problem for people who are susceptible fat cell. Rather human beings produce fatty acids in the 2008 The Author Journal compilation 2008 The International Association for the Study of Obesity. obesity reviews 9, 251–263
Good Calories, Bad Calories book review and critique G. A. Bray Fructose and weight gain: sucrose and HFCS in In the second part of his discussion of diets in Good Calories, Bad Calories, the author turns to what he calls the The second dietary component that readily produces use of ‘Unconventional Diets' and the role of insulin. He obesity in animals is access to sucrose (fructose-glucose) in highlights the work on ‘low-carbohydrate diets' published their drinking water. The response of the common labora- by Dr Pennington, Dr Robert Atkins and Dr Charlotte tory rodent to sucrose solutions is very different than when Young. Part of this discussion of very low-carbohydrate sugar is mixed with the solid ingredients in their diets (41).
diets relies on the author's earlier argument that calories Rodents love sugar-containing water. When bottles with are not the underlying basis for obesity. He says ‘But if a solutions of sucrose are available, animals drink up to 50% calorie is a calorie, why is it that a diet restricted in carbo- of their daily energy from the sucrose solution and gain hydrate . . leads to weight loss, largely if not completely weight. There is a failure to compensate when the sweet independent of calories?' A few pages later he says calories are in a drinking solution.
‘. . weight loss can be largely independent of calories'.
In the American diet, the relation of fructose to obesity His evidence that you can lose weight without reducing has been the subject of many recent publications. The intro- calories is ‘anecdotal'. What is missing in the reports that he duction of HFCS just before 1970 provided a cheap caloric cites are direct measurements of energy expenditure with sweetener that has replaced about half of the sucrose in the doubly labelled water to get around the problem of ‘under- American food supply and increased overall intake of fruc- reporting' of food intake. Also missing are measures of tose (42). The sweet taste of this mixture, made by con- ‘adherence' to the diet. The importance of adherence was verting glucose from hydrolysed starch into fructose, has nicely documented by Lyon et al. (45), who prepared food several commercial advantages. First, it is cheap to produce grown with a stable isotopic form of carbon, which allowed from corn starch. Second, the sweetness can be varied by them to measure the amount of food eaten by collecting changing the relative amount of fructose to glucose. Third, 13CO2. With this technique, they showed that the amount of it retains moisture in products better than sugar and thus weight loss was related to the adherence to the diet.
prolongs shelf life and reduces freezer burn. Fructose intake Also missing in this book is a recent review of popular has risen and with it more fructose and fat – that tasty diets by Freedman et al. (46). They showed from an analy- sweet mixture – has increased and may well be playing a sis of published diets that the levels of calories were very role in the epidemic of obesity. Almost all studies (43) show similar – in the range of 1400–1600 cal day-1 (Table 3). I a significant relationship between intake of calorie- have reproduced their table below.
sweetened soft drinks and energy intake.
In Good Calories, Bad Calories, the author views the very low-carbohydrate diets as the most beneficial dietaryapproach for weight loss and uses their effects on insulin Weight-loss diets as the basis for this view. He believes that insulin is the Do differences in dietary composition influence the rate and ‘culprit' behind the problem of obesity. Insulin is secreted degree of weight loss? In the paper titled ‘Calories do by the pancreas in response to blood glucose and the Count', Kinsell et al. (44) showed clearly that changes in glucose derived from food in the intestine. As the glucose the composition of the diet had little or no influence on absorbed from the intestine is stored in tissues stimulated weight loss when individuals were maintained in a hospital by the insulin released from the pancreas, both glucose and setting and given a fixed energy intake.
insulin return to their pre-meal levels. Fructose, which is The discussion of this problem in Good Calories, Bad half of the sugar (sucrose) molecule, or as found in HFCS, Calories comes to a different conclusion. The discussion of does not directly stimulate insulin release from the pan- diets in treating obesity in Good Calories, Bad Calories is creas. Insulin is clearly needed for synthesis of fat and for divided into two parts. In the first part of chapter 19, the storage of other nutrients after a meal. The secretion of author gives us a very nice description of the development insulin varies to keep glucose within narrow limits. Insulin of dietary treatment of obesity during the 20th century.
levels also increase in obesity.
Table 3 Data on energy intake associated
with the three major types of diets (46) High fat, low carbohydrate Low and very low fat 16–24 (10–15) 235–271 (65–75) 54–72 (15–20) 2008 The Author
Journal compilation 2008 The International Association for the Study of Obesity. obesity reviews 9, 251–263
Good Calories, Bad Calories book review and critique G. A. Bray Table 4 Comparison of maximal weight loss for several diets
Author (reference) Luscombe-Marsh (57)§ *The Samaha and Stern papers are the same population – the data from Samaha are 6 months; the data from Stern are 12 months.
†Sacks data at 18 months – moderate-fat (Mediterranean-type diet) vs. low-fat diet.
‡Six-week crossover diet in diabetics comparing high mono-unsaturated against low fat. Only the low-fat diet caused weight loss.
§Low fat/high protein (29%/35%) vs. high fat/standard protein (45%/18%).
¶Both diets contained 30% fat – the one listed as low fat had 12% protein and the one listed as low carbohydrate had 25% protein.
The question is, however, whether insulin is both neces- 8 kg (17.6 pounds) after 15 years (47). Although insulin sary and sufficient to produce obesity and whether reduced- injections will produce some weight gain, patients with carbohydrate diets are really better than other diets. That insulinoma, who secrete insulin continuously, are at most is, does the macronutrient composition of the diet matter only modestly overweight. Although insulin is ‘necessary' during weight loss? Kinsell provided his answer in 1964 for obesity, it is not ‘sufficient' and not driving the current (44) when he compared variations of diet composition epidemic of obesity (34).
within a fixed caloric intake for individuals who lived on a Are low-carbohydrate diets the most effective treatment metabolic ward for up to 6 months. He concluded that for obesity? The obvious test of this idea is to examine calories, not macronutrients, counted. In chapter 21, studies that have compared low-carbohydrate diets with Taubes tries to convince us that low-carbohydrate diets are other diets. I have summarized a number of such trials in ‘better', as he claims they lower insulin, which is the Table 4. I selected 3–6 months, as this is the period of ‘driving' force for obesity. If the thesis of Good Calories, maximal weight loss, and avoided the issues of weight Bad Calories is correct, then repeated injection of insulin maintenance. There are four published reports that have produces massive obesity. Insulin injections do produce examined the effect of diets using meta-analysis, a tech- some weight gain but also produce a significant fall in nique which allows for pooling of data from several glucose (hypoglycemia). Taubes cites the experience of studies. One meta-analysis compared 12 studies that Rony, who used insulin to increase appetite in markedly used low-calorie diets vs. a control (65). At the end of underweight patients with anorexia nervosa. There was an 12 months, the difference between control and treated increase in appetite and weight gains of 20 pounds over groups in these 12 weight-loss studies was -5.31 kg (95% 3 months, but this would still leave most anorexics under- CI -5.86 to -4.77 kg). This number of -5 kg is a good weight. The fact that it is no longer used raises concerns bench-mark for comparing macronutrient-specific studies.
about the ‘risk' of hypoglycemia vs. the ‘benefit' of the A second, larger meta-analysis focusing on ‘diet counseling' small weight gains. The weight gain with insulin in diabet- found nearly identical results with a ‘net mean treatment ics is also modest – some 5 kg (11 pounds) in 5 years and effect of approximately 2 BMI units (5 kg) of weight loss at 2008 The Author Journal compilation 2008 The International Association for the Study of Obesity. obesity reviews 9, 251–263
Good Calories, Bad Calories book review and critique G. A. Bray 1 years' (66). In a meta-analysis of six trials with low-fat into this problem. It was clear that they did not have a ‘lack diets, Pirozzo et al. (67) concluded that ‘. . low-fat diets of willpower' that is so often attributed to obese individu- are as efficacious as other weight-reducing diets for achiev- als. Rather they had a recessively inherited genetic defect ing sustained weight loss, but not more so'. In the final that drove them to eat. We now know that these animals meta-analysis (68), which examined five (49,48,53,50,64) lack the leptin receptor or leptin itself. Using myself as an of the six studies (52 not included) that have included an example of an investigator who is an endocrinologist and a ‘Atkins-like' diet, the authors found this low-carbohydrate specialist in obesity, I can state that the field of obesity diet produced a net overall effect of -3.3 kg (95% CI -5.3 research has always had people from a number of medical to -1.4). In the diets summarized in Table 4, those that disciplines, including endocrinology, gastroenterology, used generic low-carbohydrate strategies did not find sig- nephrology and surgery. In his assessment of the research nificant effects (69,70,57,58,71,60). This raises the concern agenda of this field of study, the author of Good Calories, of whether other ‘lifestyle' or ‘expectation' issues might Bad Calories seems to have misinterpreted the development have biased the outcome of the studies with ‘Atkins-like' of the field of obesity research.
diets. It is more than just the level of carbohydrate, but isundefined and does not support the central thesis of Good Calories, Bad Calories. In any case, there is certainly noimpressive difference in the effect of any diet, and one can, Although Good Calories, Bad Calories has much useful in my judgement, attribute the effects to the differences in information, the part on obesity, at least, needs to be read calories, not macronutrient composition.
and interpreted in the light of the more complete story of I would thus agree with Kinsell et al. when they said: developments in this field. The important contributionsresulting from the discovery that energy expenditure could Calories do Count.
be measured using doubly labelled water make non-sense Kinsell et al. 1964 (44) out of the claims that ‘calories don't count'. However, theenergy-balance concept does not provide the explanation for why some people become obese and others do not in thesame food environment. There are many kinds of obesity, Psychological or physiological explanations and only some depend on diet composition. Genetic factors play a role as do the contributions of other environmental One theme of Good Calories, Bad Calories is that the agents. Eating a high-fat diet and drinking sugar- or HFCS- research agenda shifted strongly to the behavioural side sweetened beverages are two of them. When diet is impor- during the 1950s and 1960s. I think this does not tant, it may be the combination of fat and fructose (the adequately describe the developments during this period.
deadly duo) that prevents energy balance from occurring.
There were clearly strong psychological and behavioural Regardless of diet, it is a positive energy balance over currents in the work of Stunkard, Stellar and Stuart. But months to years that is the sine qua non for obesity. Obese there were equally strong physiological and genetic influ- people clearly eat more than do lean people, and food- ences identified in the work of Jean Mayer and his student, intake records are notoriously unreliable. Underreporting Judy Stern, Ethan A.H. Sims and his students Elliot Dan- of food intake is greater in the obese than in normal-weight forth and Edward Horton, George Cahill and his students, people and is worse when the foods are high in fat than Thomas Aoki and Oliver Owen, Theodore van Itallie and with other macronutrients.
his students Sami Hashim and F. Xavier Pi-Sunyer, JulesHirsch and his students, M.R.C. Greenwood and Rudoph Conflict of Interest Statement
Leibel, and Edwin B. Astwood and his student, GeorgeBray. In Good Calories, Bad Calories, we are introduced to No conflict of interest was declared.
Dr Edwin B. Astwood, one of the leading endocrinologistsof the 20th century, who gave his Presidential address to the Endocrine Society in 1962 with the title ‘The Heritage 1. Short T. A Discourse Concerning the Causes and Effects of of Corpulence'. He believed that obesity and the disposi- Corpulency Together with the Method for its Prevention and Cure.
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genetically inherited obesity is where I began my work on 2. Wadd W. Cursory Remarks on Corpulence; or Obesity Con- obesity with Professor Astwood at the New England sidered as a Disease: With a Critical Examination of Ancient and Medical Center in 1962. This was the same year that he Modern Opinion, Relative to its Causes and Cure, 3rd edn. J.
Callow: London, 816 gave his Presidential Address on ‘The Heritage of Corpu- 3. Taubes G, Good Calories Bad Calories. Challenging the Con- lence'. Dr Astwood suggested that finding out why geneti- ventional Wisdom on Diet, Weight Control and Disease. Alfred A.
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SIRT1 Regulates Circadian Clock GeneExpression through PER2 Deacetylation Gad Asher,David Gatfield,Markus Hans Reinke,Charna Florian Kreppel,Raul Mostoslavsky,Frederick W. Alt,and Ueli 1Department of Molecular Biology, Sciences III, University of Geneva, 30, Quai Ernest Ansermet, CH-1211 Geneva-4, Switzerland2Division of Gene Therapy, University of Ulm, Helmholtzstrasse 8/1, D-89081 Ulm, Germany3Massachusetts General Hospital Cancer Center, Harvard Medical School, Boston, MA 02114, USA4Howard Hughes Medical Institute, Children's Hospital, Center for Blood Research, and Department of Genetics,Harvard University Medical School, Boston, MA 02115, USA*Correspondence: DOI 10.1016/j.cell.2008.06.050

Royaume du maroc

ROYAUME DU MAROC Université Mohammed V -Agdal Faculté des Sciences Juridiques, Economiques et Sociales CAHIER DES PRESCRIPTIONS SPECIALES (CPS) Appel d'offres ouvert sur offres de prix N° 03/2013 (lot unique) (Séance publique) OBJET: Achat et Installation de Matériel Informatique et de Logiciels Destinataire: Faculté des Sciences Juridiques, Economiques et Sociales Rabat-Agdal