Plain language summary
High-protein diets may promote weight loss and improved body composition via a number of mechanisms such as increasing satiety and promoting muscle synthesis. The aim of this study was to examine the effects of timed ingestion of whey protein on body weight, fat distribution, insulin resistance and hunger. A secondary aim was to assess the effect of different exercise regimes on the same outcomes. Participants were sedentary and overweight or obese, but otherwise healthy, adults. For 16 weeks, all participants consumed three 20g servings of whey protein per day; within 1 hour of waking, mid-afternoon or within 30 minutes of exercise, and within 2 hours of going to bed (P). Some participants were also assigned to an exercise regime consisting of either resistance and sprint training (RT) or a mixed regime of resistance training, interval training, stretching and endurance (RISE). All participants continued to consume their usual diets. All three groups saw improvements in markers of their body composition and cardiometabolic health, regardless of whether they exercised or not. However, the combined effects of whey protein and exercise resulted in additional improvements in visceral fat, adipokines and insulin sensitivity. Whey protein plus the mixed exercise regime (RISE) was associated with the greatest improvements and the authors concluded that this is an effective lifestyle intervention for overweight and obese adults.
Abstract
The present study examined the effects of timed ingestion of supplemental protein (20-g servings of whey protein, 3×/day), added to the habitual diet of free-living overweight/obese adults and subsequently randomized to either whey protein only (P; n = 24), whey protein and resistance exercise (P + RT; n = 27), or a whey protein and multimode exercise training program [protein and resistance exercise, intervals, stretching/yoga/Pilates, endurance exercise (PRISE); n = 28]. Total and regional body composition and visceral adipose tissue (VAT) mass (dual-energy X-ray absorptiometry), insulin sensitivity [homeostasis model assessment-estimated insulin resistance (HOMA-IR)], plasma lipids and adipokines, and feelings of hunger and satiety (visual analog scales) were measured before and after the 16-wk intervention. All groups lost body weight, fat mass (FM), and abdominal fat; however, PRISE lost significantly (P < 0.01) more body weight (3.3 ± 0.7 vs. 1.1 ± 0.7 kg, P + RT) and FM (2.8 ± 0.7 vs. 0.9 ± 0.5 kg, P + RT) and gained (P < 0.05) a greater percentage of lean body mass (2 ± 0.5 vs. 0.9 ± 0.3 and 0.6 ± 0.4%, P + RT and P, respectively). Only P + RT (0.1 ± 0.04 kg) and PRISE (0.21 ± 0.07 kg) lost VAT mass (P < 0.05). Fasting glucose decreased only in P + RT (5.1 ± 2.5 mg/dl) and PRISE (15.3 ± 2.1 mg/dl), with the greatest decline occurring in PRISE (P < 0.05). Similarly, HOMA-IR improved (0.6 ± 0.3, 0.6 ± 0.4 units), and leptin decreased (4.7 ± 2.2, 4.7 ± 3.1 ng/dl), and adiponectin increased (3.8 ± 1.1, 2.4 ± 1.1 μg/ml) only in P + RT and PRISE, respectively, with no change in P. In conclusion, we find evidence to support exercise training and timed ingestion of whey protein added to the habitual diet of free-living overweight/obese adults, independent of caloric restriction on total and regional body fat distribution, insulin resistance, and adipokines.
Methodological quality
Jadad score
:
2
Allocation concealment
:
No
