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Lower Caloric Expenditure = Better Weight Loss Results?

The phrase “Eat less, move more” is often used as a simple direction for weight loss seekers. Recent study findings present a provocative challenge to the “move more” part of that equation.

Scientists from the University of Copenhagen in Denmark decided to explore whether differences in workout length and energy expenditure would affect weight loss. “The amount of weight loss induced by exercise is often disappointing,” they said. “[We know that] a diet-induced negative energy balance triggers compensatory mechanisms, e.g., lower metabolic rate and increased appetite. However, knowledge about potential compensatory mechanisms triggered by increased aerobic exercise is limited.”

So they decided to put it to the test. They separated 61 “moderately overweight” young men into the following groups for 13 weeks: nonexercise control (n = 18); moderate exercise (n = 21; expending 300 kilocalories per day); and high-exercise (n = 22; expending 600 kcal per day). Exercise sessions lasted about 30 and 60 minutes, respectively. The scientists measured body composition, accumulated energy balance and degree of compensation. Subjects were instructed to maintain their current dietary intake and to keep a food journal.

At study completion, the moderate-exercise group had shed about 8 pounds of body weight and 8.8 pounds of fat. The high-exercise group didn’t fare as well. Although its members exercised twice as long and expended twice as many calories, they lost an average of only 6 pounds of body weight and 8.4 pounds of fat.

“Although the exercise-induced energy expenditure in [the high group] was twice that of [the moderate group], the resulting accumulated energy balance, calculated from changes in body composition, was not different,” the authors explained. “Energy balance was 83% more negative than expected in [the moderate group], while it was 20% less negative than expected in [the high group].”

And even though reported energy intake did not differ statistically between the two groups, changes achieved by the high-exercise group fell slightly short of those achieved by the moderate-exercise group. So does that mean that more exercise is not necessarily better with regard to weight loss and body composition?

“A similar body fat loss was obtained regardless of exercise dose,” the study authors concluded. “A moderate dose of exercise induced a markedly greater than expected negative energy balance, while a higher dose induced a small but quantifiable degree of compensation.”

The study was reported in the American Journal of Physiology: Regulatory, Integrative and Comparative Physiology (2012; 303 [6], R571–79).

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