by Chelsea Whyte
Meat lovers, rejoice. The long-held notion that protein-rich diets are more filling appears to be true, which means that hitting the right balance between protein, carbohydrates and fat can curb overeating.
Researchers from the University of Sydney, Australia, tested three diets on 22 male and female participants. All three diets were made up of the same meals and optional snacks, but modified to contain 10, 15 or 25 per cent protein. Each subject spent four days on each one.
When on the 10 per cent protein diet, participants reported feeling hungrier in the 2 hours following breakfast than they were on both higher-protein diets.
The menu with the least protein also caused the volunteers to snack more. From the first day to the last, participants ate a 12 per cent greater volume of food overall on this diet.
“When protein in the diet is diluted by extra fat and carbohydrate, even by a small amount – something that has happened over recent decades in westernised countries – we keep eating in an attempt to attain our target level of protein,” says Stephen Simpson, co-author of the study.
Protein on the brain
Proteins are made up of amino acids, and circulating free amino acids are known to be important in the control of appetite, says Simpson. “There are amino-acid receptors in many places within the body, including parts of the brain known to be involved in control of feeding and hunger.” Exactly how these amino acids act on the brain to suppress appetite needs investigating further, he adds.
Someone who kept eating as much as participants did on the 10-per-cent-protein diet, without doing any more exercise, would probably put on around a kilogram a month, says Simpson.
There is no need to go overboard on the steak and tuna, though – participants on the 25-per-cent-protein diet ate no less than those on the 15 per cent diet.
“Our findings have considerable implications for body-weight management in the current nutritional environment, where foods rich in fat and carbohydrate are cheap, palatable and available to an extent unprecedented in our history,” says co-author Alison Gosby.
Journal reference:
Testing Protein Leverage in Lean Humans: A Randomised Controlled Experimental Study
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