New magnetic resonance imaging (MRI) research suggests the combination of exercise and diet preserves significantly more thigh muscle volume than diet alone in overweight and obese patients at risk for knee osteoarthritis (OA).
For the study, recently published in Skeletal Radiology, researchers reviewed baseline and eight-year follow-up 3T MRI segmentations of thigh muscles in 291 overweight and obese patients at risk for knee OA. The study authors subsequently compared thigh muscle volume changes as well as the impact of diet and diet/exercise in participants who had stable weight (SW), moderate weight loss (MWL) and extensive weight loss (EWL).
Overall, the study authors noted a 12.8 percent decrease in muscle sub-volume in the EWL group (participants with > 10 percent body mass index (BMI) loss), a 10 percent decrease in the MWL cohort (those with 5 to 10 percent BMI loss) and a 5.1 percent decrease in SW study participants (BMI +/- 3 percent).
The researchers also found that study participants who combined exercise with diet modifications had 5.2 percent thigh muscle volume loss in contrast to 8.5 percent for those who utilized diet modifications alone.
“We found a doubled rate of percentage loss of muscle volume in participants with successful weight loss vs. individuals without weight loss over 8 years, and at least 25% lower rates of muscle loss in those participants who incorporated exercise in their weight-loss regimes,” wrote lead study author Katharina Ziegeler, M.D., who is affiliated with the Department of Radiology and Biomedical Imaging at the University of California San Francisco (UCSF) in San Francisco, and colleagues.
Specifically, study authors noted a 4.6 percent change in quadriceps muscle volume loss for the SW group in contrast to 9.1 percent for the MWL cohort and 12.3 percent for study participants with EWL.
Three Key Takeaways
1. Exercise preserves muscle mass during weight loss. Overweight and obese patients at risk for knee osteoarthritis who combined diet and exercise preserved significantly more thigh muscle volume than those who relied on diet alone (5.2 percent vs. 8.5 percent muscle loss).
2. Greater weight loss may lead to greater muscle loss. Patients with extensive weight loss (>10% BMI reduction) had the highest loss of thigh muscle volume (12.8 percent), highlighting the potential downside of aggressive weight reduction without muscle-preserving strategies.
3. BMI alone is inadequate for assessment. The study suggests BMI is insufficient to evaluate body composition changes in OA patients, advocating for complementary metrics like abdominal circumference, subcutaneous fat, and thigh muscle volume for a more comprehensive evaluation.
While the researchers utilized reduced BMI to define weight loss in the study, they suggested that BMI in isolation is an inadequate barometer for evaluating diet- and exercise-related changes for overweight and obese patients with OA.
“ … Drawing on different measures of body composition, such as abdominal circumference, subcutaneous fat, and thigh muscle, may provide a more complete picture of which diet- or exercise-associated changes in body composition are most beneficial to individuals with OA,” posited Ziegeler and colleagues.
(Editor’s note: For related content, see “New MRI Study Questions Use of Corticosteroid Injections for Knee OA,” “Emerging Topics in Interventional Radiology: The Role of Geniculate Artery Embolization to Treat Knee Osteoarthritis” and “MRI Shows Racket Sports Can Worsen Knee Arthritis for Some.”)
In regard to study limitations, the authors acknowledged that their multi-slice volumetric assessment offered less information on changes with hamstring and quadriceps muscles than imaging evaluation of the entire muscles. They also noted that the limited cohort size thwarted subgroup analysis of weight-loss regimes and conceded that advanced OA in the right knee was overrepresented in the group of people with extensive weight loss.
