7 January 2009

Surprising finding from calorie-weight study

by Kate Melville

An international study has failed to find supporting evidence for the common belief that the number of calories burned in physical activity is a key factor in rising rates of obesity. Researchers from Loyola University Health System and other research centers compared African-American women in metropolitan Chicago with women in rural Nigeria. On average, the Chicago women weighed 184 pounds and the Nigerian women weighed 127 pounds.

The researchers had expected to find that the slimmer Nigerian women would be more physically active, but to their surprise they found no significant difference between the two groups in the amount of calories burned during physical activity. "Decreased physical activity may not be the primary driver of the obesity epidemic," remarked Loyola nutritionist Amy Luke.

Physical activity strengthens bones and muscles, improves mental health and mood, lowers blood pressure, improves cholesterol levels and reduces the risk of cardiovascular disease, diabetes, breast cancer and colon cancer. But the new research, appearing in the journal Obesity, suggests that weight control might not be among the main benefits.

People burn more calories when they exercise. But they compensate by eating more, said Loyola's Richard Cooper. "We would love to say that physical activity has a positive effect on weight control, but that does not appear to be the case," he added.

Results of the new study are similar to those of a 2007 study of men and women in Jamaica. Researchers from Loyola and other centers found there was no association between weight gain and calories burned during physical activity. "Evidence is beginning to accumulate that dietary intake may be more important than energy expenditure level," Luke said. "Weight loss is not likely to happen without dietary restraint."

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Source: Loyola University Health System