Nutrition/Obesity
Grip strength: are some adiposity phenotypes more detrimental than others? A mendelian randomisation study Amy Taylor* Amy Taylor John Vincent Dylan Williams Rachel Cooper Snehal Pinto Pereira
Background
Improved understanding of associations between location and type of adiposity with grip strength may help identify specific underlying mechanisms and inform interventions for maintaining muscle strength.
Methods
In up to 340,258 UK Biobank participants (aged 38-73 years) of European ancestry, we investigated cross-sectional observational associations between regional adiposity (visceral, abdominal subcutaneous and gluteofemoral adipose tissue [VAT, ASAT and GFAT respectively] and anterior thigh muscle fat infiltration [ATMFI]), body fat (BF) percentage, and grip strength. We also performed Mendelian Randomisation (MR) to estimate effects of total (BF) and regional (VAT, ASAT, GFAT, ATMFI) adiposity, along with ‘metabolically favourable’ (MetFA) and ‘metabolically unfavourable’ adiposity (MetUFA), on grip strength.
Results
Higher BF percentage, MetFA and ATMFI were consistently associated with lower grip strength across observational and MR analyses. In MR analysis, an SD increase in BF was associated with a -0.12SD decrease in grip strength (95%CI:-0.16,-0.08), a one SD increase in MetFA was associated with a -0.30SD decrease in grip, (95% CI:-0.44,-0.16) and a one SD increase in ATMFI was associated with a -0.05SD decrease in grip (95% CI:-0.09,-0.01). Higher VAT was associated with lower grip in observational but not in MR analyses. Associations for higher ASAT were inconsistent: observational analyses suggested weaker grip; MR analyses indicated stronger grip (particularly in females). Higher GFAT was associated with stronger grip in observational analyses only and there was no strong evidence in MR for associations with MetUFA.
Conclusions
This study confirms the importance of muscle fat infiltration in determining muscle strength. Future interventions to improve muscle function might benefit from focusing on preventing and reducing fat infiltration in muscles. ‘Metabolically favourable’ adiposity may have detrimental consequences for muscle strength.