Why do we get fat? / Gerry Taubes

Carefully controlled studies may give us a clear answer about the cause of obesity: excess calories or incorrect carbohydrates

Why do so many of us get so fat? The answer seems clear. "The fundamental reason for obesity and excess weight," according to the World Health Organization, "is an imbalance between the number of calories consumed and the number of calories used." Or simply, either we eat too much or we are not active enough or both options are correct. According to this logic, any excess of calories, whether it comes from proteins, whether it comes from carbohydrates or whether it comes from fats (the three main food components or "nutrients"), is reflected in weight. Therefore, the solution is also clear: eat less and do more sports.

The reason to doubt this statement is also self-evident. The attitude of "eat less / move more" has prevailed for 40 years, yet the prevalence of obesity, or the accumulation of a harmful amount of fat in the body, has risen to unprecedented levels. Today more than a third of Americans are obese, more than double the number 40 years ago. And their number worldwide is greater than half a billion.

In addition to obesity, we develop metabolic disorders, that is, disorders in the body's metabolism, such as type 2 diabetes, which is characterized by hormonal abnormalities in the processes of food processing and storage and is especially common among very obese people.

The jarring situation of incompatibility between a problem that is getting worse and a solution that seems to be agreed upon on everything raises two possibilities. One, we understand correctly why people get fat, but the fat people themselves, for genetic, environmental or behavioral reasons, are unable or unwilling to heal. The other, we are wrong in our understanding and hence also in our suggestions to improve the situation.

If we are mistaken in our understanding, the cause of obesity may not be a disturbance in the energy balance but something closer to a hormonal defect, an idea adopted by European researchers before World War II. If so, the main suspect, or the environmental trigger, for such a defect is related to the amount of carbohydrates we consume and their quality. According to this version, the basic mistake we made is the assumption that it is the energy content of the food - avocado, steak, bread or fizzy drink - that causes obesity and not the effects that foods, especially carbohydrates, have on the hormones that regulate fat accumulation.

In view of the frequency with which researchers see obesity as a disturbance in the energy balance, one could assume that the idea was rigorously examined already decades ago. But such a proper scientific test has not yet been done. The experiments were too difficult and too expensive to perform properly. The researchers thought, in their typical way, that the answer is obvious, we eat too much, so the experiments are not worth the effort. Thus the scientific basis of the most pressing medical problem of our time, the skyrocketing rates of obesity and diabetes and the complications they cause, remains virtually unknown.

After ten years of researching the science and its history, I am convinced that a real development in the study of obesity will only be achieved if we rethink and carefully examine how we understand its causes. In 2012, I co-founded a non-profit organization called the Nutrition Science Initiative (NuSI) with Peter Atiyeh, a former surgeon and cancer researcher, to address the issue of missing evidence. With the support of the Laura and John Arnold Foundation of Houston, Texas, we recruited independent scientists to design and conduct experiments that would grammatically and rigorously test the competing hypotheses about obesity (and weight gain in general). The Arnold Foundation has committed to finance up to 60% of NuSI's ongoing research budget and three years of operating expenses totaling $40 million. The investigators will follow the evidence wherever it is. If everything goes as planned we will be able to obtain unequivocal evidence for the biological causes of obesity within the next six years.

The hormone theory

To understand what makes the hormone theory of obesity so appealing, we need to understand where the energy balance theory fails. The idea that obesity is caused by consuming more calories than the body utilizes seemingly stems from the first law of thermodynamics, according to which energy cannot be created and cannot disappear. In the world of biology, the law is reflected in the ability of the energy that a living being needs to convert itself in a useful way (that is, to be used for metabolism in the body) or to be emitted from the body or stored in it. Therefore, if we consume more energy than we use or emit, the excess should be stored, which means we will get fat and gain weight. So far everything is clear. But the law says nothing about the reasons why we put more calories into our bodies than we take out, and it doesn't say why the excess is stored as fat. These are the questions that await answers.

And more precisely: the question of why the fat cells accumulate fat molecules as a reservoir of excess energy is a biological and not a physical question. Why do those fat molecules not go through a process of metabolism to create useful energy or emit heat? And why do the fat cells store excess fat in certain areas of the body and not in others? Saying that they do this because we have consumed too many calories is not a meaningful answer.

To answer these questions, the role of hormones, especially insulin, in stimulating the fat accumulation process in different cells must be taken into account. Insulin is secreted in response to a sugar called glucose. When the blood glucose level rises, as happens after eating a high-carbohydrate meal, the pancreas secretes more insulin, whose role is to keep the blood glucose level from rising to a dangerous level. The insulin instructs the muscles, organs and even the fat cells to take in more glucose and use it as fuel. It also instructs the fat cells to store fat, including the fat eaten at that meal, for use at a later time. As long as the insulin level remains high, the fat cells hold the fat and the other cells give priority to burning glucose (and not fat) for energy.

The main sources of glucose in food are starch, cereal grains and sugars. (In the absence of carbohydrates, the liver will produce glucose from proteins.) The easier the carbohydrates are to digest, the greater and faster the rise in blood glucose. (Compared to fiber and fat in food, which slow down the process.) Therefore, food rich in grains and processed starches will increase insulin secretion. Sugars, such as sucrose (ordinary table sugar) and high-fructose corn syrup (used in the US, for example, to sweeten many industrial products, such as snacks and soft drinks - the editors), play a central role because they contain fructose, which undergoes a metabolic process mainly in the liver cells . Research results suggest, although not with certainty, that high levels of fructose are an important factor in "insulin resistance". When the cells are resistant to insulin, more insulin is needed to regulate the glucose level. The result, according to the hormone theory, is that in increasingly longer periods of time during the day, the level of insulin in the blood remains high, so the fat continues to accumulate in the fat cells instead of fueling the body. A small amount of 10 to 20 calories a day stored as excess fat can cause obesity within a few decades.

The hormone theory suggests that the way The unit To prevent this deterioration and return the situation to normal is to avoid eating sugars and carbohydrates, which raise insulin levels. This way the body will naturally burn the stored fat for fuel. According to this logic, the transition from burning carbohydrates to burning fats can happen even when the overall amount of calories consumed does not change. Cells burn fat because that's what the hormones actually tell them to do; And so the energy expenditure in the body increases. From this point of view, in order to lose body fat, the amount of carbohydrates must be limited and replaced, preferably with fat, which does not stimulate insulin secretion.

This alternative theory of obesity implies that the ongoing worldwide epidemics of obesity and type 2 diabetes (and growing to large proportions due to insulin resistance) are driven primarily by the grains and sugars in our food. She also implies that the first step in preventing these crises is avoiding the consumption of sugars and limiting the consumption of starchy vegetables and grains. The amount of food and the degree of sports activity should worry us less.

Forgotten history

The energy balance theory was not always the prevailing theory. Until World War II, the members of the Samka were active in the study of obesity (and in most areas of medical research) in Europe, and they came to the conclusion that obesity, like any other growth disorder, is caused by a defect in hormonal regulation. They believed that something was wrong with the hormones and enzymes that regulate the storage of fat in the fat cells.

Gustav von Bergmann, a German internist, developed the original theory nearly a century ago. (Currently, the highest award given by the German Society of Internal Medicine is the Gustav von Bergmann Medal.) Bergmann coined the term "lipophilia", which literally means "love of fat", to describe the affinity of different tissues in the body for fat accumulation. Just as we only grow hair in certain areas of the body, we store fat in certain places and not in others. This "lipophilic tendency", he hypothesized, must be controlled through physiological factors.

The idea of ​​lipophilia disappeared after World War II, when English replaced German as the international scientific language. On top of that, the technologies needed to understand the control of fat accumulation in fat cells, especially the technique to accurately measure the levels of fatty acids and hormones in the blood, were not invented until the late 50s.

In the mid-60s it was already clear that insulin was the main hormone in regulating fat accumulation, but then obesity was already considered an eating disorder that had to be treated by persuasion or coercion to eat fewer calories. When the studies linked the amount of cholesterol in the blood to the risk of heart disease, and nutritionists labeled saturated fat as responsible for all the evils, the authorities began to recommend a low-fat diet anda petition carbohydrates. The idea that carbohydrates May cause obesity (or diabetes or heart disease) thrown aside.

And yet, some doctors embraced the carb/insulin theory and wrote nutrition books advising obese people to eat as much as they wanted as long as they avoided carbs. Since most influential experts believed that these people got fat in the first place because they ate as much as they wanted, these diet books were seen as frauds. The most famous of them, Robert S. Atkins, did not really contribute to this school of thought when he claimed that you can eat saturated fat to your heart's content, such as Newburgh lobster dishes (made with butter, sweet cream and liqueurs) and double cheeseburgers, as long as you avoid eating sugars. In the eyes of many, his proposal was considered criminal medical negligence.

Careful experiments

In the last twenty years, evidence has accumulated suggesting that these nutritionists were right, that the hormone theory is a reasonable explanation for obesity and that insulin resistance, probably caused by sugars in the diet, is a fundamental defect not only in type 2 diabetes but also in heart disease and even cancer. These findings indicate that it is of utmost importance to carry out careful experiments that will examine the role of carbohydrates and insulin resistance in obesity. Since the main goal is to identify the environmental causes of obesity, the experiments should be aimed at clarifying the processes that are responsible for the accumulation of excess fat. Since obesity can develop over decades, the increase in fat at monthly follow-up can be too small to detect. Therefore, the first step of the NuSI-funded researchers will be to test the competing theories in a way that will result in faster weight loss. These first results will help determine which experiments are needed to further clarify the mechanisms at work and which of the theories is correct.

An initial key trial will be carried out by researchers at Columbia University in collaboration with the US National Institutes of Health (NIH, the Florida Sanford-Burnham Hospital Institute for Applied Research in Orlando and the Pennington Center for Biomedical Research in Baton Rouge, Louisiana. Throughout the trial in this study there will be 16 subjects who are obese or suffer from excess weight in a research facility and under laboratory conditions to ensure an accurate assessment of the amount of calories they consume and the amount of energy they use. In the first stage, the participants will eat food similar to that of an average American: 50% carbohydrates (of which 15% sugar), 35% fat and 15% protein. The researchers will carefully "play" the incoming calories until it is clear that the participants neither gain fat nor lose fat, meaning that the amount of incoming calories is equal to the amount of calories used, according to measurements that will be made in a facility called a metabolic cell. In the second stage, the participants will receive food with a caloric value The same, and the number of meals and the number of snacks will not change either, but the composition of the food will be completely different.

The carbohydrate content of the new diet will be very low, about 5%, meaning the amount of carbohydrates found naturally in meat, fish, chicken, eggs, cheese, animal fat and vegetable fat, which will be served with green leaves. The protein content will be the same as it was in the first stage, 15% of the calories. The rest, 80% of the calories, will come from fat found in these actual food sources. The idea is not to examine whether this diet is healthy or sustainable for a lifetime, but only to lower the insulin levels for maximum reduction in the shortest possible time.

Ideally, meaningful scientific experiments should distinguish between the results predicted by competing theories. In our case, if the accumulation of fat is due to an energy imbalance, the participants will neither gain nor lose weight because they will eat exactly the same amount of calories they use. Such a result will support the accepted theory, that a calorie is a calorie, whether it comes from fat, whether it comes from carbohydrate or whether it comes from protein. But if the composition of the nutrients affects the accumulation of fat, then during the carbohydrate restriction phase the participants should lose weight as well as fat and their energy utilization will increase. Such a result would support the idea that calories derived from carbohydrates are more fattening than those derived from fat or protein, probably due to the effect of insulin.

One of the disadvantages of this rigorous scientific approach is that there is no possibility of rushing without making unacceptable compromises. Even this initial trial will last almost a year. The more ambitious subsequent experiments will last another three years. As we raise more funds we hope to support more trials, including focusing on the role certain sugars and macronutrients have in other disorders, such as diabetes, cancer and neurological problems. No such experiment will be easy, but the experiments are doable.

One overarching goal is to assure the general public that any nutritional advice they receive - for weight loss, general health or obesity prevention - will be based on rigorous science and not on prejudice or blind consent. Obesity and type 2 diabetes not only burden the individuals who suffer from them but also place a heavy burden on the public health system and the economy. We desperately need unequivocal evidence, such as the NuSI experiments were designed to provide, if we are to combat and prevent these disorders.

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About the author

Gerry Taubes is one of the founders of the Nutrition Science Initiative and the author of the book "Why We Get Fat and What to Do About It" (Knopf Publishing, 2011).

in brief

What is the most important cause of obesity: too much food or eating the wrong types of food, especially easily digestible carbohydrates?

Although nutrition researchers think they know the answer, the question has never stood a rigorous scientific test - until now.

Researchers will soon try to answer the question with the funding of the Nutrition Science Project. They will precisely control the food intake of volunteers under laboratory conditions and then carefully measure the energy they use and how it changes in different food compositions.

More on the subject

Insulin and Insulin Resistance. Gisela Wilcox in Clinical Biochemist Reviews, Vol. 26, no. 2, p. 19-39; May 2005. www.ncbi.nlm.nih.gov/pmc/articles/PMC1204764

Obesity and Energy Balance: Is the Tail Wagging the Dog? JCK Wells and M. Siervo in European Journal of Clinical Nutrition, Vol. 65, no. 11, p. 1173-1189; November 2011.

The article was published with the permission of Scientific American Israel