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Exercise doesn't help weight loss
How the body compensates
After exercise, the body's metabolism slows and it tries to regain the energy that was lost. Hunger works the same way: a walk before a meal builds an appetite, as parents have always said. That is how evolution built the body, and it is why changing the diet is what moves weight.
Where exercise does help
One caveat holds up. After someone has improved their diet and lost weight, keeping up some exercise does help prevent the weight from creeping back. On its own, without a change in diet, it is of no use for weight.
Exercise remains great for mood, for the heart, and against cancer, among other things. The idea that it is the route to weight loss is a huge myth, and gyms and fitness apps have spread it. A group of ten friends who tracked their workouts for a year saw almost no one lose any weight.
Why does the body compensate for exercise?
In a 2012 study in PLoS ONE, anthropologist Herman Pontzer and colleagues measured the daily energy burn of Hadza hunter-gatherers in Tanzania and found it matched that of people in Western countries, despite far more daily activity. In 2016, his team analyzed data from more than 300 adults in Current Biology and proposed that the body holds total daily energy expenditure within a narrow range. When activity rises, spending on other tasks such as immune function and repair appears to shrink. This is called the constrained energy model.
How do people who keep weight off use exercise?
The National Weight Control Registry, started in 1994 by Rena Wing and James Hill, tracks thousands of adults who lost at least 30 pounds and kept it off for a year or more. Most members report high levels of physical activity, often around an hour a day of walking or similar exercise. They also report eating a lower-calorie, lower-fat diet and weighing themselves regularly.
Why does exercise still protect the heart?
Regular exercise lowers resting blood pressure, improves how muscles take up glucose, and raises HDL cholesterol. It also lets the heart pump more blood per beat, so the resting heart rate falls. A 2011 analysis in The Lancet by Chi Pang Wen and colleagues followed more than 400,000 people in Taiwan and linked even about 15 minutes of daily activity to lower mortality than inactivity.
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