Whey protein is not only superior to soy for trimming down, but may help maintain or even promote weight loss regardless of intake of calories.
Protein has long been associated with increased satiety, thereby improving weight loss and promoting adherence to difficult, otherwise hunger-inducing diets. While protein may keep you fuller longer, a new study in the July issue of The Journal of Nutrition, showed that whey protein is more effective than soy protein when it comes to weight loss.
Researchers from the United States Department of Agriculture randomly assigned 90 participants to consume soy protein (SP), whey protein (WP), or carbohydrate (CHO) supplements at mealtime for 23 weeks. Total calorie consumption was not reduced or restricted—all participants were overweight or obese at the start of the intervention.
“This study suggests that after 6 mo of supplementation, there was a difference in body weight and fat mass between overweight and obese adults who consumed supplemental WP compared to those who consumed isoenergetic supplemental CHO,” the authors report.
The scientists didn’t observe similar weight-reducing results in the group that consumed soy protein or carbohydrate.
At the end of the trial, the whey protein group lost 4 more pounds in body weight and 5 more pounds in fat mass than the carbohydrate group.
“Additionally,” the researchers wrote, “consuming WP resulted in a significantly smaller waist circumference compared with the group consuming supplemental CHO.”
As found in this study, macronutrient (protein, carbohydrate or fat) choices can make an impact on body composition. Not only is protein thought to be satiating and thermogenic, whey protein consumption without calorie restriction had a favorable impact on body weight. The researchers emphasize that in the WP supplementation group “the difference in body weight was associated with a decrease in fat without an effect on lean mass.”
The authors write that protein is key to short-term weight loss because it reduces the urge to overeat and that the impact of whey protein on body weight without calorie restriction or the intention to lose weight is novel.
“Protein supplementation, particularly WP, in overweight and obese individuals may assist in long-term maintenance of body weight without energy restriction,” the researchers suggest.
Reference: Baer DJ, Stote KS, Paul DR, et al. Whey Protein but Not Soy Protein Supplementation Alters Body Weight and Composition in Free-Living Overweight and Obese Adults. J Nutr 2011, 141 (7). doi: 10.3945/jn.111.139840