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)

Abstract

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 e35 kg/m 2 ), aged 30e70 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 ¼ 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.

Whole Grain Consumption and Inflammatory Markers: A Systematic Literature Review of Randomized Control Trials

“…Consumption of whole grains in preference to refined grains is known to have improved health benefits, with the broad range of benefits often attributed solely to the presence of dietary fiber [10,53]; however, other components, phytochemicals, fatty acids, amino acids, vitamins, and minerals are all likely to play a role. This review of 31 RCTs found that consumption of whole grain foods had a moderate effect on reducing inflammatory markers, with five of the possible 15 crossover studies [33,38,40,42,50], and seven of 16 parallel studies demonstrating statistically significant changes [23,[29][30][31][32]43,49]. Within the population groups studied, the reduction in markers was most often observed in obese and overweight populations, and among those with pre-existing conditions, compared with studies of healthy populations, although there were only two studies in this category.…”

“…Previous systematic reviews and meta analyses, performed by Rahmani et al [17] and Hajihashemi et al [18] utilising publications up until 2019, found little evidence of a relationship between whole grain consumption and inflammatory markers. The current review included a total of 13 papers not included in the aforementioned reviews [17,18], six of which were published outside the timeframe utilized by the previous authors [30,31,41,43,44,52], and a further seven were included in the current review due to a variation in the search strategy [23,29,37,39,42,45,51].…”

“…Only three of the 31 studies noted that subjects were instructed to maintain weight for the duration of the study [27,29,42], and only one study controlled for weight in their analysis [50], with all others showing a slight decrease in weight or no data mentioned. In addition, only eight studies recorded or mentioned physical activity or exercise, with six asked to maintain [23,25,27,30,33,41], one asked to record any exercise [32], and one asked to refrain completely [29]. A change in weight either through diet or exercise could be a possible confounder, as it becomes difficult to isolate the changes in inflammatory status as a result of the consumption of whole grain or as a result of the weight (fat) loss [57].…”

“…The included studies were assessed against the predetermined criteria of the Cochrane RoB2 tool for randomized control and crossover trials [21]. Within Domain 1: Randomization Process, there were five studies with some concerns of bias [24,28,30,31,43], with the remaining studies (n = 26) with a low risk of bias. In Domain 2: Deviations from intended intervention, there was one study with a high risk of bias [22], one with some concern [31], and the remainder with a low risk of bias (n = 29).…”

“…Among the 16 studies in the overweight and obese populations (BMI 25-35), two had two intervention arms [22,47], resulting in 18 studies within this category (Table 3). All 18 studies measured CRP levels, with six of these (33%) observing a statistically significant reduction in CRP levels following whole grain consumption [29,30,32,33,38,40]. Nine of the studies measured IL-6 levels, with one observing a statistically significant change in IL-6 levels after consumption of whole grain foods [40].…”