Exercise helps health, but weight? Not so much.

Our waistlines aren’t expanding because people aren’t exercising intelligently or vigorously enough… The idea that our obesity epidemic is caused by sedentary lifestyles has spread widely over the past few decades, spurring a multibillion-dollar industry that pitches gadgets and gimmicks promising to walk, run and kickbox you to a slim figure. But those pitches are based on a myth. Physical activity has a multitude of health benefits — it reduces the risk of heart disease, Type 2 diabetes, high blood pressure and possibly even cancer — but weight loss is not one of them.

I was introduced to this idea, that a lack of exercise isn’t the reason for our growing waistlines, while reading Gary Taubes (Good Calories, Bad Calories and Why We Get Fat). Even though he backed his claim with research, I found it hard to accept.

But the evidence just keeps coming.

From 2001–2011, researchers discovered that Americans, overall, increased activity (exercise). At the same time, obesity levels increased.

The increased physical activity is a boon to health, because it has a “positive independent impact on the health of Americans as it will reduce the burden of cardiovascular diseases and diabetes.” But the correlation between physical activity and obesity is low. “Other changes such as reduction in caloric intake are likely needed to curb the obesity epidemic and its burden” (Population Health Metrics, 2013).

A 2013 econometric study found that sugar in the food supply was directly correlated with diabetes. For every additional 150kcal/person/day of sugar in the food supply (that’s one can of sugared soda), there was a 1.1% increase in diabetes. No other foods were correlated with diabetes. The researchers wrote: “Differences in sugar availability statistically explain variations in diabetes prevalence rates at a population level that are not explained by physical activity, overweight or obesity” (PLoS ONE, 2013).

Although this research sounds like common sense, it’s the first I’ve seen with such an air-tight correlation.

Exercise alone not reduce weight. Moreover, research suggests that globally “poor diet now generates more disease than physical inactivity, alcohol and smoking combined” (British Journal of Sports Medicine, 2015).

In 2010, David Katz, MD (Yale) wrote something similar: “The modern world makes it very easy to out-eat exercise, and nearly impossible to out-exercise excessive eating.” Katz is the founding director of the Yale University Prevention Research Center.

“Even if a junk food diet, conjoined to daily exercise, allowed for maintenance of an ‘ideal’ weight, it would not do the same for the more important measure: health,” he wrote. “Food is the fuel that runs the human machine in its diverse and elaborate functions, and high-quality performance across that range of biological actions requires high-quality fuel.”

There are clear health-related benefits to exercise. But you are unlikely to achieve weight loss without improving your food intake.

• It is time to bust the myth of physical inactivity and obesity: you cannot outrun a bad diet, British Journal of Sports Medicine (2015), doi:10.1136/bjsports-2015-094911
• Prevalence of physical activity and obesity in US counties, 2001–2011: a road map for action, Population Health Metrics (2013), doi 10.1186/1478-7954-11-7.
• The Relationship of Sugar to Population-Level Diabetes Prevalence: An Econometric Analysis of Repeated Cross-Sectional Data, PLoS ONE (2013), doi:10.1371/journal.pone.0057873.

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