The scientific evidence for the effectiveness of higher protein has been building steadily over the past few years. One study by Donald Layman, Ph.D., a professor of nutrition at the University of Illinois Urbana-Champaign, is a good example. The comparative study looked at two different weight-loss approaches.
Twenty-four overweight women aged 45 to 46 participated in the study. Half followed the standard carbohydrate-based diet recommended by the USDA: 60 percent carbohydrates, 30 percent dietary fat and 10 percent protein. The other half followed a reduced carb, higher-protein diet: 40 percent carbohydrates, 30 percent fat and 30 percent protein. (This translates into about 170 grams of carbohydrates a day), The diets were matched for calories; the women in both groups ate 1,700 calories a day.
After 10 weeks, the researchers found that women in both groups had lost an average of 16 pounds each. There were some crucial differences between the two groups, however. On average, the standard-diet group lost 10.4 pounds of that weight in body fat and 3 pounds in muscle mass. The reduced carb higher protein group on average, though, lost much more body fat—12.3 pounds—and lost much less muscle mass—only 1.7 pounds. When analyzed as ratios, these numbers are even more telling. The reduced carb higher protein dieters had a very favorable 7 to 1 ratio of body fat loss to muscle mass loss; in the high carb group, the ratio was a much less desirable 3.5 to 1.
Why is this important? Because muscle is metabolically more active than fat. The more muscle you have, the faster you burn calories, the faster you lose weight and the easier it is to keep the weight off.
Not only that, overall the lower carb group showed a slight increase in their HDL ("good") cholesterol levels and a significant decrease in triglycerides, or fat in the blood. Because the combination of low HDL and high triglycerides is a major risk factor for heart disease, improving these numbers is very important. The high-carb group also showed improvements in cholesterol levels—but none in triglycerides.
Finally, the lower carb higher protein group showed an increase in thyroid hormone levels. Because this hormone helps control metabolism, higher levels suggest a higher rate of metabolism, which helps weight loss by burning off calories faster.
The results of Dr. Layman's study were presented in April 2001 at the prestigious annual meeting of Federation of American Societies for Experimental Biology, and have since been published in the Journal of Nutrition.1 In his presentation, Dr. Layman commented, "The protein diet was twice as effective. Women eating the lower protein diet were less capable of burning calories at the end of the study as when they started it."
- Layman D.K., Boileau, R.A., Erickson, D.J., et al., "A Reduced Ratio of Dietary Carbohydrate to Protein Improves Body Composition and Blood Lipid Profiles During Weight Loss in Adult Women)," The Journal of Nutrition, 133(2), 2003, pages 411-417.