Introduction Diet-induced weight loss is a first-line treatment for overweight and obesity, but it is often associated with loss of lean body mass. This raises questions about possible effects of diet-induced weight loss on muscle function, notably strength because of its correlations with mortality, and whether any such effects remain long term.
Methods This clinical trial (NCT02030249) investigated the effects of an 8-week weight reducing meal replacement diet providing 3,390 kJ (810 kcal) per day on muscle strength in 77 overweight/obese (body mass index (BMI) ≥ 25 kg/m2) pre-diabetic men and women aged 25-70 years. Handgrip strength was measured with a hydraulic hand dynamometer immediately after the weight reducing diet (8 weeks) and at 26 weeks (i.e. 4 months after completion of the diet).
Results BMI at baseline was 37.0 ± 7.8 kg/m2. The 8-week diet induced an average body weight loss of 11.6 ± 4.0 kg relative to baseline, and at 26 weeks weight was 12.4 ± 6.9 kg less than at baseline. Handgrip strength was significantly reduced at 8 weeks in both hands, with the effect being larger in the dominant (-1.8 ± 3.23 kg, p<0.005) than in the non-dominant hand (-0.84 ± 3.21 kg, p<0.05). Sex and age had no effect on these outcomes for handgrip strength. At the 26-week time point, handgrip strength was still reduced relative to baseline values in both the dominant and non-dominant hand.
Conclusion Significant reductions in handgrip strength occurred after an 8-week weight reducing diet in pre-diabetic overweight and obese adults, and the effect had not dissipated at 4 months after completion of the diet. This highlights the need for long-term follow-up studies to determine whether any diet-induced reductions in muscle strength persist over time, as well as the possible long-term implications for balance and performing activities of daily living.