Author of several bestsellers in the United States, Gary Taubes is an American journalist specializing in scientific investigation. He has spent a large part of his career investigating nutritional recommendations. His position as a journalist, outside medical circles, offers him the freedom necessary to question official dogmas. As he publishes a new book, Rethinking Diabetes (“Rethinking Diabetes”, Penguin Random House), he returns for L’Express to the origins of these two modern epidemics: obesity and diabetes, and is concerned about the “revolution” of new anti-diabetes drugs. obesity.
L’Express: What do you think are the causes of the current obesity epidemic? More than 40% of Americans are obese according to the Centers for Disease Control and Prevention…
Gary Taubes: Two paradigms clash. The majority theory is that the food industry has made too much tasty food available to us and that we also have too little physical activity. So we are getting bigger. The alternative view, which I hold, sees obesity as a hormonal condition, primarily driven by insulin, in response to the type of carbohydrates we eat. We have a food system dominated by refined carbohydrates, from white flour to sugar. The more refined the carbohydrates, the easier they are to digest and the higher insulin levels rise.
In your opinion, serious errors were made in the nutritional recommendations. For what ?
This idea of an imbalance in the energy balance was born in Germany in the 1930s, and then spread to the United States. Then the Germans began to reject it, but the Americans adopted it without reservation, and based all their recommendations on it. We were told that it was just a question of gluttony, laziness, and excess food. After the Second World War, this concept triumphed. In the 1960s, leading obesity researchers, psychologists and psychiatrists, tried to understand why people with obesity ate so much. In 1994, leptin was identified. This discovery has been interpreted as the discovery of a hormone that tells the brain when to stop eating. Once again, we try to explain why fat people can’t stop eating, with the idea that everything happens in the head.
Today, new drugs against obesity, GLP-1 analogues, prove that losing weight is not just a question of willpower. We are told that these drugs work because they cause people to eat less. But in reality, people who take them have suppressed appetites before they even eat, they simply don’t feel hungry. The food did not have time to enter and leave their intestines. So there is plenty of evidence that the effect of these drugs is much more profound.
You also denounced the obsession with fats, and particularly saturated fats…
In the 1960s and 1970s, American scientists concluded that saturated fats were the cause of heart disease, even though the French and Swiss – large consumers of cheeses rich in saturated fats – had one of the highest life expectancies in the world. world. To avoid heart disease, it was therefore necessary to follow a diet low in saturated fats. The authorities decided that it was too complicated to explain to people to avoid just saturated fats, so they were told to avoid all fats, indiscriminately. We have thus replaced these calories with carbohydrates, even though we have a certain amount of evidence that the latter make us gain weight. All of this eerily coincides with the current epidemic of obesity and diabetes.
What do you think of these new obesity drugs? Is this a revolution?
Very clearly. But sometimes some revolutions produce worse results than before. Obesity is a very difficult burden to reverse. I believe that a low-carb diet can be effective. But even if I’m right, we don’t know if this would be enough to significantly reduce the share of the population who are overweight. Conversely, these medications make things quite easy. And when it’s easy, people take it in droves.
But when you disrupt a very important homeostatic system, as these drugs seem to do, you can never know the long-term consequences. If you try to stop them, the weight comes back in most cases. But what happens after ten, twenty years of treatment? With benzodiazepines or opioids, we have found that the longer you take them, the more problems you have, with side effects that change over time.
The situation seems worrying to me. Do you know the phrase attributed to Donald Rumsfeld, former United States Secretary of Defense? “The known unknowns and the unknown unknowns.” This is a great way to sum up the fact that sometimes you know you don’t know things, but other times you don’t even know enough yet to know that you don’t know. The “unknown unknowns” of GLP-1 analogues may or may not be minor…
“We have never really identified the cause of the obesity epidemic”
But could we stop this obesity epidemic without drugs?
To prevent an epidemic, we must first identify the cause. However, we have never really identified the cause of the obesity epidemic. Once again, the conventional wisdom prevails that people eat too much and don’t exercise enough. In this approach, it therefore comes down to personal responsibility. In my first book in 2007, Good Calories, Bad Calories, I explain that refined carbohydrates and sugars are the drivers of this epidemic. But I was told that it’s hard to blame refined sugars, because all of Southeast Asia has a high-carb diet, without epidemics of obesity and diabetes until recently. How can we explain that these billions of people do not become obese and diabetic by consuming white flour and white rice, which are high glycemic index carbohydrates? David Ludwig, an endocrinologist at Harvard who works on the glycemic index, points out that these people also have very active lifestyles. Those who eat the most carbohydrates and the cheapest carbohydrates are also those who physically work in the rice fields. This could be true.
But we can also think that these people have not consumed Coca-Cola for a long time. By adding sugary drinks to a country’s diet, we see an epidemic of obesity and diabetes within a few generations. There are biochemical reasons to incriminate these products. This is my view, but it is very difficult in practice to test what causes obesity in humans.
In addition, another factor must be taken into account, called fetal programming. Simply put, mothers who are overweight or obese, who gain a lot of weight during pregnancy, or who are diabetic or have gestational diabetes, will pass on to their child a greater predisposition to becoming obese and diabetic as they grow up. This concept, first developed in the 1920s in Denmark, is one reason your doctor will try to limit weight gain during pregnancy.
The problem is that with this fetal programming, each generation has an increased risk of becoming obese and diabetic at a younger age. People today are born with a greater predisposition to obesity and diabetes than before. If we want to reverse the course of the epidemic, we must start with the mother and during pregnancy.
Pregnancy is actually one of the things that makes me very nervous about these new medications. A young woman takes these GLP-1s, loses 15 kilos and then wants to have a child. We have no idea what effects these drugs have on fetal programming. Perhaps they will reverse the transmission of this predisposition, making the next generation thinner. But another possibility is that the young woman wants to become pregnant, that she talks to her doctor and that he stops her medication. And now she gains weight during pregnancy. In any case, this is the kind of study that needs to be carried out on these drugs.
What do you think are the impacts of physical activity and sport?
When we do observational cohort epidemiological studies, we take a population and follow it over time. We then discover that slender people are those who are physically active. We therefore assume that there is a causal link. But we could also, conversely, assume that lean, healthy people are physically active because they can be.
In animal studies, making an animal physically active will not prevent it from becoming obese if it has a genetic predisposition, even by exhausting the animal! But as humans, we live in a world of very active, skinny people who think that if fat people did like them, everything would be fine. Believe me, everyone who struggles with obesity would like this to be true. But the data shows that those of us who gain weight easily are just different from skinny people.
So many mistakes have been made when it comes to nutrition. We were told that fats are bad because they are high in energy density, and that we should replace them with carbohydrates. We removed the fat from the yogurts. But since it makes them taste terrible, we added sugar. These low-fat products are marketed as a health food, believed to prevent heart disease. And now most of our calories come from sugar…
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