Can exercise alone prevent metabolic disease?
The narrative that exercise alone can prevent obesity and metabolic disease is largely the product of food industry PR campaigns; scientific evidence indicates sugar and carbohydrate consumption, specifically, contributes to disease progression.
In this 2015 editorial, Aseem Malhotra, Tim Noakes, and Stephen Phinney argue that in addition to exercise, specific dietary changes are necessary to prevent or reverse metabolic disease.
A 2015 report from the Academy of Medical Royal Colleges described exercise as a “miracle cure” and argued 30 minutes of moderate exercise five times per week is more powerful than pharmaceuticals for chronic disease management and prevention. Malhotra et al. argue the emphasis on exercise distracts from the primary role diet plays in the causation and potential reversal of cardiovascular disease, Type 2 diabetes, dementia, some cancers, and other metabolically influenced conditions.
Over the past 30 years, Western obesity rates have risen while mean physical activity levels have remained relatively constant. Companies such as Coca-Cola have nonetheless pushed the narrative that lack of exercise is the cause of obesity, obesity is the cause of chronic disease, and no foods or beverages are uniquely harmful so long as we exercise enough to burn the calories they contain. In other words, consumers can continue to drink sugar-sweetened beverages as long as they exercise more.
This tactic is similar to that used previously by Big Tobacco and reflects a concerted effort to sow public doubt and confusion about the clear scientific links between sugar/refined carbohydrates and chronic disease. For one, obesity itself is far from a perfect predictor of disease risk, with 40% of lean individuals presenting dyslipidemia, insulin resistance, and other markers of poor metabolic health. Recent econometric analysis has indicated an increase in sugar consumption across a population increases diabetes risk 11-fold compared to a similar increase in fat or protein consumption (the analysis meets the Bradford Hill criteria for inferring causality from observational data). Recent reviews have argued carbohydrate restriction is a uniquely potent tool for reversing metabolic disease. The work of Noakes and others has even shown carbohydrate is not required for intensive exercise, as individuals adapted to low-carb diets can oxidize enough fat to meet the demands of all but the most intense levels of exertion.
Malhotra et al. conclude public health officials and marketing efforts should reveal the truth: that the framing of exercise as the single solution to metabolic disease is the result of food industry PR campaigns. The solution to the metabolic disease epidemic is likely to come from a reduction in sugar and refined carbohydrate consumption rather than an increase in physical activity without a corresponding change in eating patterns and behaviors.