Gastric bypass surgery leads to improved strength, physical performance

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Relative muscle strength and physical function improve in adults after Roux-en-Y gastric bypass surgery, according to findings published in The Journal of Clinical Endocrinology & Metabolism.

“In addition to the metabolic and cardiovascular risks incurred by obesity, there are well-established associations between obesity and impaired skeletal muscle quality, poor physical performance and higher risk of functional decline, suggesting that bariatric surgery-induced weight loss could potentially lead to improvements in these parameters,” Diana L. Alba, MD, clinical instructor in the division of endocrinology and metabolism in the department of medicine at the University of California, San Francisco, and colleagues wrote. “However, while there is profound loss of fat mass after bariatric surgery, there is also substantial loss of lean mass, including muscle mass, raising the possibility of a negative effect on muscle strength and physical performance.”

Alba and colleagues conducted a prospective cohort study of 47 adults (mean age, 45 years; mean BMI, 44.1 kg/m2; 79% women) who underwent Roux-en-Y gastric bypass surgery at the University of California, San Francisco, or the San Francisco Veterans Affairs Medical Center.

Measurements for height, weight, handgrip strength, gait speed, physical performance, physical activity and dietary intake were collected before surgery and at 6 and 12 months after the procedure.

Handgrip strength, which was used as a measure of absolute muscle strength, was measured using a Jamar hand dynamometer. Handgrip strength was also used to determine relative muscle strength, which was calculated in two ways: by dividing absolute muscle strength by BMI and by appendicular lean mass.

Gait speed was assessed by asking participants to walk 4 m at a usual pace. Physical performance was measured by a standing test or a 400-m walking test. In the standing test, participants were asked to stand five times in succession from a seated position as quickly as possible without using their arms. Physical activity level and dietary intake were both assessed via questionnaire.

After surgery, the participants had a mean percentage weight loss of 30% and a 66% decrease in excess body weight.

The researchers found a decline in mean absolute muscle strength at 6 months (–11.9%; 95% CI, –6.3 to –17.5) and 12 months (–8.8%; 95% CI, –3.4 to –14.1) after surgery, but relative muscle strength improved both when calculating using BMI (31.9% at 12 months; 95% CI, 24.3-39.6) and appendicular lean mass (9.2% at 12 months; 95% CI, 2.8-15.7).

Besides improvements in relative muscle strength, the researchers found that mean gait speed increased from 1.1 m per second before surgery to 1.3 m per second at 12 months after surgery, making for a 13.3% improvement (95% CI, 6.5-20). Participants also took nearly 2 seconds less at 12 months after surgery to complete the standing test (11.6 seconds) compared with before surgery (13.4 seconds; P < .01). A smaller sample of participants (n = 15) completed the 400-m walking test, but the researchers noted a 14.3% improvement (95% CI, 8.6-20) in the time it took to complete the test at 12 months after surgery compared with preoperative measures.

Although strength and physical function both improved, the researchers did not find a significant change in self-reported physical activity at either time point after surgery. Dietary protein intake decreased after surgery at 6 months (52 g per day) and 12 months (49 g per day) compared with presurgical levels (78 g per day; P < .01), but the percentage of total kilocalorie intake from protein increased from 16.7% before surgery to 20.3% at 6 months after surgery (P < .01). The increase did not remain significant at 12 months, however.

“Despite declines in lean mass and absolute muscle strength after [Roux-en-Y gastric bypass surgery], both relative muscle strength and physical performance improve substantially. The magnitude of the physical performance improvements is clinically significant and suggests that [Roux-en-Y gastric bypass surgery] improves a person’s ability to perform activities of daily living,” the researchers wrote. “No clear predictors of physical performance changes were identified, so we propose that the observed physical performance improvements may result from changes in biomechanics, which simply make it easier for a person to move around and to perform physical tasks.” – by Phil Neuffer

Disclosures: The authors report no relevant financial disclosures



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