Thigh-muscle volume change in response to diet, exercise, and weight-loss in overweight and obese individuals-8-year follow-up data from the Osteoarthritis Initiative.

OBJECTIVES

Weight loss is considered an essential treatment component for knee osteoarthritis (OA), but data on weight-loss-associated changes in skeletal muscle is sparse. This study aimed to assess volumetric changes in major thigh muscle groups during weight loss.

METHODS

Included in this longitudinal analysis of the Osteoarthritis Initiative were participants who had (a) stable weight (SW) (body mass index (BMI) ± 3%); (b) moderate weight loss (MWL) (5-10% BMI); (c) extensive weight loss (EWL) (> 10%) and available segmentations of thigh muscles on MR imaging for baseline and 8-year follow-up. Exclusion criteria included Kellgren and Lawrence score > 3, baseline BMI < 25, and severe comorbidities. Linear regression was used to compare mean percentage change of muscle sub-volume between weight change groups and between different weight loss methods (diet/exercise alone or combined), adjusted for age, gender, baseline BMI, and race. Standardized response means (SRM) for volumetric and cross-sectional area (CSA) muscle changes were calculated.

RESULTS

Two-hundred-ninety-one participants were included. Decrease in muscle sub-volume over 8 years was 5.1% [95% CI - 6.0, - 4.2] for SW, 10.0% [- 11.3, - 8.6] for MWL, and 12.8% [CI - 15.0, - 10.5] for EWL. Individuals who reported diet and exercise had less muscle loss than those with diet alone (5.2% vs. 8.5%; p = 0.036). SRM was higher for volumetric (0.91-0.94) than CSA (0.40-0.48) quantification.

CONCLUSION

Loss of skeletal muscle volume during aging in increased in individuals with or at risk for knee OA who lose weight. Participants who reported exercise exhibited less muscle loss than those who reported dieting alone. Volumetric muscle quantification was more robust than CSA.