Effects of Consuming a High Protein Diet With or Without Soy Protein on Transformative Weight Loss and Maintenance; a Non‐Inferiority, Randomized Clinical Efficacy Trial

Abstract

High‐protein diets are frequently used for weight management due to their ability to enhance energy expenditure and promote lean mass retention. Compared to their animal‐based counterparts the plant‐based protein, soy, demonstrates equivalence for appetite and satiety, however, limited data exist regarding their comparative effects on volitional weight loss and maintenance. This 12‐month randomized, non‐inferiority clinical trial sought to compare the relative efficacy of consuming supplemental soy vs. other types of protein as part of a high‐protein diet and the State of Slim transformative weight management program. The primary outcome was relative change in body weight after 4‐months of interventional weight loss. Exploratory outcomes were weight change at 12 months, blood pressure, lipids, C‐reactive protein, body composition and personal wellness. Using a non‐blinded, two‐arm design with a non‐inferiority margin of Δ ≤ 3% for relative change in weight at 4 months, 58 women and 13 men aged 42 ± 9.4y with a baseline BMI of 32.9 ± 3.6 kg/m2 (mean ± SD), were asked to consume 3 servings of pre‐made soy or non‐soy protein foods (~20g protein/serving via powder, bar or patty) per day for 12 months. Body composition was assessed via dual x‐ray absorptiometry and personal wellness via validated questionnaires. All assessments were made within ± 10 days of each endpoint. Intention to treat (ITT) and completer (C) analyses demonstrated both diets were comparable for relative weight change at month 4 [ITT (N=71): soy, n=36, −6.98 ± 5.22%; non‐soy, n=35, −7.15 ±5.72%, Δ= 0.16% (90% CI: −2.0,2.33); C (N=57): soy, n=29, −8.67 ± 4.35%; non‐soy, n=28, −8.93 ± 4.9%, Δ= 0.26% (90% CI: −1.8, 2.33)]. These results indicate that the regular consumption of soy protein is comparably efficacious to other protein for volitional weight loss fostered through the State of Slim weight management program.Support or Funding InformationSupport: DuPont Nutrition & Health, St. Louis, MO