We know what makes us fat — too many calories and too little exercise — right? Maybe not. We don’t seem to be making much progress in the war on obesity, so perhaps we have overlooked something.

Overweight and obesity are not caused by consuming too many calories, but instead by the release of insulin, a release brought about by our consumption of sugars such as sucrose and high fructose corn syrup. That's what Gary Taubes, a respected science writer, argues in an essay in the British Medical Journal.

Not only is our understanding of the cause of obesity incorrect, according to Taubes, but if we are to have any success conquering obesity, the misconception must be set straight, so more effective approaches to weight-loss can be developed.

The history of obesity is a history of two competing ideas. One, the energy balance approach we are all familiar with, focuses on calories. The other emphasizes endocrinology — the role our hormones play in weight gain and fat metabolism.

War Sidelines A Budding Theory on Obesity

The metabolic approach to obesity is rooted in the discovery of insulin in the early 1920s. Before World War II European scientists were on their way to showing that obesity was a hormonal and regulatory disorder. But with the war and the rise of English as the language of science after the war, European studies on hormones and obesity fell into obscurity.

Since the 1950s weight gain has been viewed as the result of consuming too many calories, and the basis for most diet programs that overeating is the cause of obesity has been the accepted belief, even though in the 1960s insulin was identified as the primary regulator of the accumulation of fat in adipose cells. Had the theory survived, we might now see refined, high-glycemic grains and sugars as triggers for obesity; instead of simply pointing the finger at excessive calorie consumption.

Do people get fat because they are eating more, or do people eat more because the composition of their diet is causing a hormonally-induced increase in fat accumulation?

It is well accepted that simple carbohydrates drive insulin levels upward, and so could actually increase fat storage and, indirectly, appetite.

Taubes explains, “The point is that the hormones directly increase the storage of fat in fat tissue. The result of this is an increase in appetite…[G]rowing children are often voraciously hungry, but they don’t grow because they eat so much; they eat so much because they’re growing.”

In other words, people don't get fat because they are eating more, they eat more because the composition of their diet is causing a hormonally-induced increased appetite and fat accumulation. It appears to explain why sugar-sweetened beverage consumption is highly correlated with obesity. For progress toward winning the war on obesity to occur, the possibility of this cause of obesity must be studied, argues Taubes. Anything less than stellar scientific research should not be accepted.

“With the burden of obesity now estimated at greater than $150 [billion] (£100bn; €118bn) a year in the US alone,” Taubes writes, “virtually any amount of money spent on getting nutrition research right can be defended on the basis that the long term savings to the healthcare system and to the health of individuals will offset the costs of the research by orders of magnitude.”

Gary Taubes is co-founder of the Nutrition Science Initiative, a non-profit organization whose purpose is " …to answer the question definitively of what constitutes a healthy diet." In addition to his science reporting, for which he has won the Science in Society Award of the National Association of Science Writers three times, he is the author of Why We Get Fat and Good Calories, Bad Calories.