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. © 2016 World Obesity