Exercising More Doesn’t Necessarily Lead To Weight Loss

(Reuters Health) – Increasing physical activity to burn more calories works up to a point, but then the body adjusts to keep energy use stable, according to a new study.

As a result, people who are extremely active burn a similar number of calories as only moderately active people, researchers say. And for people trying to modify their weight, increasing exercise will not translate to endless increases in calories expended.

In a previous study, lead author Herman Pontzer of Hunter College at the City University of New York found that people in subsistence farming or hunter-gatherer societies, who are moving around and walking great distances for much of the day, have similar daily calorie burn to people in developed countries who are more sedentary.

“When I first got into this area with hunter gatherers in Tanzania, we measured daily energy expenditures and they were very physically active every day,” but weren’t burning more calories than adults in the U.S. or Europe, Pontzer told Reuters Health by phone.

For the new study, Pontzer and colleagues studied energy expenditure in 332 adults, aged 25 to 45 years, drawn from populations in Ghana, South Africa, Seychelles, Jamaica and United States.

They measured total energy expenditure using specially “labeled” water, and measuring how the water molecules are eliminated over time in saliva, urine or blood samples. The researchers also tested exhaled carbon dioxide to measure resting metabolic rate and had the subjects wear accelerometers to record daily activity levels.

The researchers found that for less active people, energy expenditure increased alongside increases in physical activity. But at higher levels of activity, calorie burn plateaued.

Resting metabolic rate tended to be constant at 1,540 calories per day, and activity increased calorie burn up to 2,600 calories per day, at which point additional activity didn’t appear to burn any more calories, according —> Read More