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Surgery and muscle strength

Gastric bypass improves muscle strength and physical performance

The study sought to examine changes in body composition, strength, physical activity and physical performance 12 months following RYGB

Roux-en-Y gastric bypass (RYGB) improves relative muscle strength and physical performance in people with obesity, according to a study led by researchers from the University of California, San Francisco, San Francisco, CA. However, as well as resulting in dramatic weight loss, the surgery also results in lean mass and absolute grip strength decline.

The study, "Changes in Lean Mass, Absolute and Relative Muscle Strength, and Physical Performance After Gastric Bypass Surgery," published in the Endocrine Society's Journal of Clinical Endocrinology & Metabolism, sought to examine changes in body composition, strength, physical activity and physical performance 12 months following RYGB.

"Our research found while Roux-en-Y bariatric surgery patients are likely to see the maximum amount of strength they can exert decline as they lose weight, they actually see an increase in their relative strength - a measure of strength relative to their size," said the study's first author, Dr Diana Alba of the University of California, San Francisco (UCSF). "Our participants' physical performance also improved following surgery. The findings suggest that postoperative loss of muscle mass and absolute strength may not be a meaningful problem."

In the prospective cohort study, researchers examined the body composition, handgrip strength, physical activity and physical performance (chair stand time, gait speed, 400-meter walk time) of 47 obese adults (37 women, 10 men, aged 45 ± 12 years (mean ±SD) and BMI44±8), before and six and 12 months after gastric bypass surgery. Relative strength was calculated as absolute handgrip strength divided by BMI and also as absolute strength divided by appendicular lean mass.

Patients experienced substantial 12-month decreases in total body weight (-37±10 kg or 30±7%), fat mass (-48±12% of baseline) and total lean mass (-13±6%). Mean absolute grip strength declined by 9±17% (p<0.01). In contrast, relative muscle strength increased by 32±25% (strength/BMI) and 9±20% (strength/ALM) (p<0.01 for both). There were statistically and clinically significant postoperative improvements in all physical performance measures, including mean improvement in gait speed of >0.1m/s (p<0.01) and a decrease in 400m walk time of nearly a full minute (from 5.3±0.7 to 4.4±0.7 min, p<0.01).

"Having good muscle strength and physical function is essential to helping people carry out their day-to-day lives," added Alba.

Other authors of the study include: Lucy Wu, Kathleen Mulligan, Thomas Lang, Jonathan T Carter, Stanley J Rogers, and Andrew   Posselt of UCSF; Peggy M Cawthon of UCSF and the California Pacific Medical Center in San Francisco, CA; Sheena Patel of the California Pacific Medical Center; Nicole J King of the San Francisco Veterans Affairs Health Care System in San Francisco, CA; and Lygia Stewart, Dolores M Shoback, and Anne L Schafer of UCSF and the San Francisco Veterans Affairs Medical Center.

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