Effects of high-intensity training and a high-protein diet on body composition, muscle metabolism and muscle strength in overweight adults: a systematic review and meta-analysis

Abstract

The increase in high-intensity training (HIT) guidelines and the use of hyperproteic diets (HPDs) as a treatment of excess weight in adults have generated interest in their effects on body composition, metabolic profile and muscular strength. So, the objective of this study was to determine the effects of HIT together with an HPD on the body composition, muscle metabolism and muscle strength of overweight or obese subjects. According to that, a standardized search of randomized controlled trials was carried out considering: 1) application of a HIT protocol, 2) compliance with an HPD and 3) their combined application in non-active overweight or obese subjects. Screening was then carried out by two independent researchers, following the criteria in the Cochrane handbook for systematic reviews of interventions. Data was extracted from the 8 studies selected which were systematically reviewed, and subsequent meta-analysis was performed. A statistically significant decrease in body fat (6 studies which included n=294 subjects; MD -0.56 kg; 95% CI -0.90 to -0.22 kg; p=0.001; I2 =18%; Chi2=6.08; p=0.30) and an increase in lean body mass (7 studies which included n=370 subjects; MD 0.37 kg; 95% CI 0.02 to 0.72 kg; p=0.04; I2 =55%; Chi2=13.42; p=0.04) were detected. Sensitivity analysis confirmed the significance of these results. No statistically significant changes were observed in any of the other variables studied. Despite the statistically significant decrease in body fat and increase in lean body mass, not statistically or clinically significant improvements were observed in the other variables, not even in those where favorable changes had been reported in previous studies. For obtaining more conclusive results in future meta-analysis, it will be necessary to carry out new studies with less variable and better-defined HIT and HPD protocols in order to increase comparability. These studies should control subjects’ diet conveniently, especially protein and energy intake.