The science of obesity: what do we really know about what makes us fat?
If we are to make any progress in tackling the obesity crisis, we have to look again at what really makes us fat, claims an article published in this week's BMJ.
Gary Taubes, co-founder of the Nutrition Science Initiative, argues that our understanding of the cause of obesity may be incorrect, and that rectifying this misconception is "absolutely critical" to future progress.
"What we want to know," he says, "is what causes us to gain weight, not whether weight loss can be induced under different conditions of semi-starvation."
The history of obesity research is a history of two competing hypotheses of energy balance and endocrinology, writes Taubes. Since the 1950s, conventional wisdom on obesity has been that it is caused by a positive energy balance – in other words we get fat because we overeat. The alternative hypothesis – that obesity is a hormonal or regulatory disorder – was dismissed after the second world war as being unworthy of serious attention.
But Taubes believes that the wrong hypothesis - energy balance - won out and that it is this hypothesis, along with substandard science, that has fuelled the obesity crisis and the related chronic diseases.
He argues that attempts to blame the obesity epidemics worldwide on increased availability of calories "typically ignore the fact that these increases are largely carbohydrates" and, as such, these observations "shed no light on whether it's total calories to blame or the carbohydrate calories."
Nor do they shed light on the more fundamental question of whether people or populations get fat "because they're eating more, or eat more because the macronutrient composition of their diets is promoting fat accumulation … in effect, driving an increase in appetite."
Taubes also points to "substandard" research that is "incapable of answering the question of what causes obesity."
As a result, he has co-founded the Nutrition Science Initiative, a not-for-profit organisation to "fund and facilitate rigorously well controlled experimental trials, carried out by independent, sceptical researchers." Our hope, he says, is that these experiments will answer definitively the question of what causes obesity, and help us finally make meaningful progress against it.
If we are to make progress in the struggle against obesity and its related chronic diseases, he believes we must accept the existence of alternative hypotheses of obesity, refuse to accept substandard science, and find the willingness and the resources to do better.
"With the burden of obesity now estimated at greater than $150bn (£100bn; €118bn) a year in the US alone, 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," he concludes.