Bariatric surgery is one of the most successful long-term treatments for severe obesity. Of the large reduction in weight, about 24-42% is thought to be fat-free mass (FFM), and about 90% of FFM lost is skeletal muscle mass (SMM). Exercise interventions during the rapid weight loss following bariatric surgery suggest that exercise does not attenuate the loss of FFM. However, eccentric exercise may potentially attenuate the loss of SMM because the higher force production may stimulate hypertrophy.


All participants began 6–8 weeks after undergoing Roux-en-Y gastric bypass or sleeve gastrectomy. SMM in lower body was measured via magnetic resonance imaging (MRI). Nineteen females (age = 37.6 ± 9.8 yr, height = 164.4 ± 7.2 cm, weight = 106.9 ± 15.6 kg) were randomly assigned to one of three groups: eccentric exercise (ECC; n = 6), concentric exercise (CON; n = 7), or standard-of-care control (SCC; n = 6). Exercise groups performed 30-minute lower body exercises sessions three times per week for 16 weeks. At the end of 16 weeks, all participants repeated baseline testing for SMM.


Thirteen individuals completed the study. All groups lost weight: ECC: 21.8 ± 3.3 kg (p < 0.001); CON 19.9 ± 4.0 kg, and SCC 21.4 ± 3.7 kg (all p < 0.001). Skeletal muscle mass decreased in all groups: ECC: 0.90 ± 0.5 kg (p = 0.09), CON: 1.19 ± 0.6 kg (p = 0.06), and SCC: 0.77 ± 0.5 kg (p = 0.18). There were no significant differences in SMM change between intervention groups. The skeletal muscle loss in percent of total weight loss was 3.7 ± 4.1%.


Some SMM loss still occurred regardless of resistance training, but the loss was less than anticipated.