What is really the cause of obesity (the aetiology of obesity)? This is not a question most people think about because they assume they already know the answer. Too many calories causes obesity, they think. Of course, if it were true, then cutting calories would reverse the obesity epidemic. That, unfortunately, did not happen.

The entire obsession with calories was a 50 year dead end. We can only start to address the problem of weight loss and gain by understanding the real causes. So what is the real cause of obesity? Let’s go back in time and see what people thought about obesity in the past.

William Banting 1796–1878 is considered to have written the first diet book. He started off as a normal weight fellow in his teens and 20’s. However, as he went through his 30’s, 40’s and 50’s he started to gain some weight. Not much, but a few pounds per year. Before long, he was age 62 and weighed 202 pounds. Not bad by modern standards, but a real chunky monkey by the standards of that time. So, on the advice of his physicians, he tried to eat less. But then, he felt tired, hungry and he wasn’t really losing any weight. Then, he tried to exercise more. He rowed the Thames and became quite physically fit. However, he was still not able to keep the weight off. Finally, on the advice of a French surgeon, he started a new diet. He would severely restrict not calories, but sugars and starches — what we now call refined carbohydrates. He avoided all breads, milk, beer, sweets and potatoes. Poor fellow loved his carbs, too.

He lost so much weight and felt so well that he decided to publish his findings in “Letter on Corpulence Addressed to the Public“. This pamphlet was really the first modern diet book. Based on personal experience, Banting felt that it was not calories that caused weight gain, but refined carbohydrates. Many of his ideas that sugars and starches caused obesity persisted through the next 100 years of so. Sir William Osler — the influential Canadian physician who wrote “The Principles and Practice of Medicine” — illustrates that most doctors of the early 1900’s considered that refined carbohydrates were the chief cause of obesity. In his famous textbook, he described treatment of obesity with diets predominantly featuring meat and eggs and low in refined carbohydrates. In his 1882 monograph “Obesity and its Treatment” Dr. Osler felt that fatty foods were crucial to reducing obesity because they increased satiety (feeling of fullness). Contrast this to the modern demonization of dietary fats. This coincides neatly with the obesity epidemic. Maybe the good Dr. Osler was onto something after all. By the 1950’s it was fairly standard advice. If you were to ask your grandparents ‘back in the day’ what caused obesity, they would not talk about calories. Calories as a unit of energy was largely unknown at that time. They would say instead, that sweets and starchy foods caused obesity. Dr. Spock’s Baby and Child Care — a bible of child rearing of the 1950s — describes the gaining or losing of weight as mostly dependent upon the amount of desserts and plain, starchy foods consumed. Dr. Passmore in the British Journal of Nutrition in 1963 wrote the “Every woman know that carbohydrate is fattening”. Every. Woman. Knows. This was no secret. Everybody knew it. These ideas had withstood the test of time. Common sense and empiric observation served to confirm the truth of the matter. The ideas were “Anti-Fragile” as the great Nassim Taleb puts it. And obesity wasn’t such a great problem back then. This is what they thought:

Things started to change in the 1950s. There was a perceived increase in the incidence of heart disease. Whether this is actually true or not is debatable. Nevertheless, people started to search for the reason behind this ‘great epidemic’ of heart disease. Their gaze soon fell upon dietary fat. The “Diet-Heart Hypothesis” started to gain traction in the 1960s. Ancel Keys, a very influential nutrition ‘expert’ played an instrumental role in popularizing these ideas. With great enthusiasm and shaky science, the demonization of dietary fat (a food that humans had been eating since, well, we became humans) started. There was a problem, though we didn’t see it at the time. Dietary protein tends to remain fairly constant in human diets. It is actually quite difficult to increase dietary protein to more than 20–30% of calories without resorting to protein bars/ shakes etc. So, if one were to restrict dietary carbohydrates, then one must increase dietary fats and vice versa. This is the result: Low Fat = High Carb and Low carb = High Fat

Since dietary fat was now the villain of the hour, the ‘Heart Healthy’ recommended diet became a high carbohydrate one. Since carbohydrates in the Western hemisphere tended to be refined, we ate more and more low fat bread and pasta. After all, we weren’t giving up hamburgers for cauliflower and kale, but for bread and big plates of pasta. Through the 1950’s and 1960’s scientific debate (occasionally very acrimonious) raged back and forth. Some believed that dietary fat was the villain where others, such as John Yudkin believed that refined carbohydrates were the problem. His book, “Pure, White and Deadly — How Sugar is Killing Us” is eerily prescient, and should certainly win the award for Best Book Title — Ever.

The vitriol sometimes reached extreme levels. Jean Mayer, PhD of Harvard once likened the carbohydrate reduced diet “in a sense, equivalent to mass murder”. Just a little extreme….The American Heart Association felt that these diets were also dangerous fads. Umm…dude….really? A 200 year old fad? Ideas that had withstood the test of time? Dietary fats that humans had been eating for, like, a bazillion years? That’s what was killing us? Didn’t it occur these geniuses that if dietary fat was going to kill us, it would have already done so in the preceding, oh, 1 million years?

The low-fat diet, of course, up until that point in time was completely untested in humans. Nobody in history had ever decided to lower the fat content of their diet for health reasons. We had no idea what effect it would have. Of course, this was around the time that we also believed that we could make a more nutritious substance for babies than breast milk. That we were somehow smarter than 20 million years of evolution. So, instead of eating natural fats such as cream, butter, and olive oil we turned to purely artificial oils like margarine. Of course, these turned out to kill us with trans-fats but that is a story for another time. We moved away from natural fat and towards refined carbs. So who won? You already know the answer, and we are all the worse off for it.