Effect of diet-induced weight loss on muscle strength in adults with overweight or obesity – a systematic review and meta-analysis of clinical trials

We conducted a systematic review and meta-analysis to identify how diet-induced weight loss in adults with overweight or obesity impacts on muscle strength. Twenty-seven publications, including 33 interventions, most of which were 8–24 weeks in duration, were included. Meta-analysis of seven interventions measuring knee extensor strength by isokinetic dynamometry in 108 participants found a significant decrease following diet-induced weight loss (−9.0 [95% confidence interval: −13.8, −4.1] N/m, P < 0.001), representing a 7.5% decrease from baseline values. Meta-analysis of handgrip strength from 10 interventions in 231 participants showed a non-significant decrease (−1.7 [−3.6, 0.1] kg, P = 0.070), with significant heterogeneity (I2 = 83.9%, P < 0.001). This heterogeneity may have been due to diet type, because there was a significant decrease in handgrip strength in seven interventions in 169 participants involving moderate energy restriction (−2.4 [−4.8, −0.0] kg, P = 0.046), representing a 4.6% decrease from baseline values, but not in three interventions in 62 participants involving very-low-energy diet (−0.4 [−2.0, 1.2] kg, P = 0.610). Because of variability in methodology and muscles tested, no other data could be meta-analyzed, and qualitative assessment of the remaining interventions revealed mixed results. Despite varying methodologies, diets and small sample sizes, these findings suggest a potential adverse effect of diet-induced weight loss on muscle strength. While these findings should not act as a deterrent against weight loss, due to the known health benefits of losing excess weight, they call for strategies to combat strength loss – such as weight training and other exercises – during diet-induced weight loss.