A hypocaloric diet rich in high fiber rye foods causes greater reduction in body weight and body fat than a diet rich in refined wheat: A parallel randomized controlled trial in adults with overweight and obesity (the RyeWeight study).

Background and aim: A high intake of whole grain foods is inversely associated with body mass index (BMI) and body fat in observational studies, but mixed results have been found in interventional studies. Among whole grains, rye is the richest source of dietary fiber and meals containing high-fiber rye foods have shown increased satiety up to 8 h, compared to meals containing refined wheat products. The aim of the study was to determine the effect of consuming high fiber rye products, compared to refined wheat products, on body weight and body fat loss in the context of an energy restricted diet. Methods: After a 2-week run-in period, 242 males and females with overweight or obesity (BMI 27–35 kg/m2), aged 30–70 years, were randomized (1:1) to consume high fiber rye products or refined wheat products for 12 weeks, while adhering to a hypocaloric diet. At week 0, week 6 and week 12 body weight and body composition (dual energy x-ray absorptiometry) was measured and fasting blood samples were collected. Subjective appetite was evaluated for 14 h at week 0, 6 and 12. Results: After 12 weeks the participants in the rye group had lost 1.08 kg body weight and 0.54% body fat more than the wheat group (95% confidence interval (CI): 0.36; 1.80, p < 0.01 and 0.05; 1.03, p = 0.03, respectively). C-reactive protein was 28% lower in the rye vs wheat group after 12 weeks of intervention (CI: 7; 53, p < 0.01). There were no consistent group differences on subjective appetite or on other cardiometabolic risk markers. Conclusion: Consumption of high fiber rye products as part of a hypocaloric diet for 12 weeks caused a greater weight loss and body fat loss, as well as reduction in C-reactive protein, compared to refined wheat. The difference in weight loss could not be linked to differences in appetite response. Clinical trial registration: www.clinicaltrials.gov, Identifier: NCT03097237.