Lean Mass Loss and Altered Muscular Aerobic Capacity after Bariatric Surgery

Introduction: Patients undergoing weight loss surgery do not improve their aerobic capacity or peak oxygen uptake (VO(2)peak) after bariatric surgery and some still complain about asthenia and/or breathlessness. We investigated the hypothesis that a post-surgery muscular limitation could impact the ventilatory response to exercise by evaluating the post-surgery changes in muscle mass, strength, and muscular aerobic capacity, measured by the first ventilatory threshold (VT). Methods: Thirteen patients with obesity were referred to our university exercise laboratory before and 6 months after bariatric surgery and were matched by sex, age, and height to healthy subjects with normal weight. All subjects underwent a clinical examination, blood sampling, and body composition assessment by dual-energy X-ray absorptiometry, respiratory and limb muscle strength assessments, and cardiopulmonary exercise testing on a cyclo-ergometer. Results: Bariatric surgery resulted in a loss of 34% fat mass, 43% visceral adipose tissue, and 12% lean mass (LM) (p < 0.001). Absolute handgrip, quadriceps, or respiratory muscle strength remained unaffected, while quadriceps/handgrip strength relative to LM increased (p < 0.05). Absolute VO(2)peak or VO(2)peak/LM did not improve and the first VT was decreased after surgery (1.4 +/- 0.3 vs. 1.1 +/- 0.4 L min(-1), p < 0.05) and correlated to the exercising LM (LM legs) (R = 0.84, p < 0.001). Conclusions: Although bariatric surgery has numerous beneficial effects, absolute VO(2)peak does not improve and the weight loss-induced LM reduction is associated to an altered muscular aerobic capacity, as reflected by an early VT triggering early exercise hyperventilation.