Weight Gain Due to Calories, Not Protein Intake

January 6, 2012

A JAMA study finds no benefit of higher protein intake on fat loss.

One thing is sure: intake of dietary calories will influence weight gain. But the notion that protein can affect body fat has hit a snag, thanks to a new study published in JAMA, the Journal of the American Medical Association.

In a randomized controlled trial funded by Louisiana State University and the USDA, 25 healthy and weight-stable adults, ages 18 to 35, were assigned to overfeed on diets containing 5%, 15%, or 25% of energy from protein. Over eight weeks, researchers measured body composition and energy expenditure in each subject.

The aim of the study was to determine whether changes in protein intake would affect body fat in patients in a controlled setting.

Compared to subjects consuming low protein (5%), subjects consuming higher amounts of protein saw increased body protein levels and resting energy expenditures-as expected. But body fat increased similarly across all three groups. The logical assumption is that those gains came from calorie increase, not protein increase, according to laed researcher George Bray, PhD, of the Pennington Biomedical Research Center in Baton Rouge:

“Among persons living in a controlled setting, calories alone account for the increase in fat; protein affected energy expenditure and storage of lean body mass, but not body fat storage.”

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