Don’t skimp on protein when you diet: It may help you lose more flab and less muscle, new studies show. Harness your hunger. A diet that’s 30% protein (similar to the Zone, Atkins, and South Beach plans) helped 19 overweight people lose an average of 11 pounds, 8 of them fat. Remarkably, the subjects consumed 441 fewer calories per day in 3 months on this regimen than they had during 2 weeks on a 15% protein diet–despite the fact that they could eat as much as they wanted, provided they maintained the 30% protein ratio. Protein can suppress appetite in ways that carbs and fats can’t, the scientists say, for reasons yet to be determined.

Pick better proteins.One of protein’s amino acids, leucine, may be the key to keeping muscle and losing fat. Twenty-four women who averaged 107 g of protein daily (similar to high-protein diets) lost 1 more pound of fat than 24 others who averaged 57 g a day over 4 months. Both groups limited calories to 1,700 a day. Other recent studies show that leucine can promote muscle building when overall calories are low. Although animal protein is richest in leucine (1,700 to 2,100 mg per serving), it’s also a prime source of heart-harming sat fats. So stock up on good, lower-fat sources.

7 protein foods high in fat-fighting leucine (mg)

  • Tofu, firm, 1/2 cup – 1,511 mg
  • Cottage cheese, 1% fat, 1/2 cup – 1,440 mg
  • Fat-free milk, 8 ounces – 818 mg
  • Mozzarella, reduced-fat, 1 ounce – 670 mg
  • Cheddar, reduced-fat, 1 ounce – 608 mg
  • Egg, hard- or soft-boiled, large – 538 mg
  • Couscous, cooked, 1 cup – 464 mg