Soy High-Protein Diet Supports Weight Loss, Maintenance in New Study

Photo © iStockphoto.com/Diane Labombarbe

A new study¹ published in Obesity Science and Practice found that a high-protein diet is essential to maintaining weight loss. The study found that a calorie-restricted, high-protein diet, with or without soy protein, may improve body composition and cardiometabolic health, while also helping to keep weight off over time. DuPont Nutrition and Health (St. Louis, MO) funded the non-inferiority, randomized clinical trial, and provided the soy protein foods used in the study.

In a press release from DuPont, the company stated that one of the most important factors contributing to weight loss is the ability to lose body fat while sparing lean muscle tissue. Previous studies have shown that incorporating high-protein foods in a weight-loss plan can help subjects lose weight without losing muscle mass. In this study, researchers sought to evaluate the efficacy of incorporating soy protein–based foods in a high-protein, calorie-restricted diet for weight loss, compared to other sources of protein, in overweight or obese adults.

A total of 71 adults were assigned to one of two experimental diets: a high-protein diet including three daily soy-protein products, or a high-protein diet restricted in soy-protein products.  The soy-protein products consisted of a packet of protein powder, a protein bar, and a frozen protein patty containing 20 g of lean, high-quality soy protein per serving. The study period consisted of four months of voluntary weight loss and eight months of weight loss maintenance. All participants participated in the State of Slim weight-management program, which is a “16‐week group‐based, lifestyle modification program.”

After the first four months of following the State of Slim weight-loss program, participants began the maintenance phase. According to the study authors, the subjects were recommended to: eat high-quality foods; keep their activity levels high; weigh themselves every day; set a “take action” weight (a weight at which they would re‐engage weight loss efforts); and “be a role model.”

Throughout the study, researchers recorded subjects’ body weight, total daily protein consumption, and supplemental protein consumption (supplemental soy or non-soy protein servings per day) to determine adherence to the diet protocol. In order to assess the efficacy of the high-protein and high-protein-with-soy diets, the researchers measured subjects’ fasting body weight, body composition, fat distribution, and blood pressure, and collected blood samples in a series of in-person visits.

The results demonstrated that both groups who consumed a high-protein, calorie-restricted diet lost “similar and significant” amounts of body weight, most of which was fat mass. Although some of the subjects regained weight during the self-directed, eight-week maintenance phase, there were no significant differences between the dietary treatment groups for any of the health outcomes measured in the total 12-month trial. In addition, both the high-protein and the high-protein-with-soy groups lost roughly 3%-4% body fat. Participant also maintained an average of 4 kg fat loss throughout the 12-month study period.

Wrote the study authors: “These results indicate that soy‐based protein foods can be effectively incorporated into an energy‐restricted, high‐protein diet for improving body weight, body composition, and cardiometabolic health.”

In the press release from DuPont, Ratna Mukherjea, technical fellow, DuPont, added that “lean sources of high-quality protein, such as soy, support improvements in body composition with greater loss of fat tissue versus lean tissue.”

According to DuPont, soy protein has been shown to be comparable in efficacy to other protein sources for weight loss in healthy, middle-aged overweight and/or obese adults, and can help to support other health outcomes, including cardiovascular health. Further, it said, these study results are promising for dieters “who choose to follow dietary advice to increase consumption of plant sources.”

“A major take-home message from this study is that people following a plant-inclusive or plant-based high-protein diet can be successful in reducing body weight,” added James O. Hill, PhD, the study’s senior author. “This study was more about long-term wellness associated with weight reduction. A major struggle for dieters is maintaining their new weight and all the health benefits that accompany weight loss over time.”

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References:

1. Speaker KJ et al., “Effects of consuming a high-protein diet with or without soy protein during weight loss and maintenance: a non-inferiority, randomized, clinical efficacy trial,” Obesity Science & Practice. Published online May 12, 2018.