Impacto de la cirugía bariátrica sobre la condición física asociada a la salud y la variabilidad del ritmo cardiaco en adultos con obesidad severa

Abstract

The worldwide increase in the prevalence of obesity observed in the last five decades has led it to reach pandemic proportions. Obesity has consistently been associated with multiple morbidities, autonomic dysfunction, a significant deterioration in physical fitness and, consequently, a reduction in life expectancy. To treat obesity, particularly severe obesity, bariatric surgeries (BS) have been developed and increased, which have been shown to generate a significant reduction in body weight, which is usually the main indicator of success in obesity treatments, and an improvement in comorbidities. However, there is still no clarity on the impact of bariatric surgery on cardiorespiratory fitness, muscle strength, and heart rate variability. Considering that these parameters have a predictive value for health, the purpose of this doctoral thesis is to determine the changes in physical fitness and heart rate variability in adults with obesity, together with analyzing whether variations in these health indicators are associated to weight loss after bariatric surgery. To meet this objective, two systematic reviews and meta-analyses were conducted, as well as a cohort study with women who underwent sleeve gastrectomy. In the latter, handgrip strength and knee extensors (through dynamometry), cardiorespiratory fitness (through ergospirometry) and heart rate variability (by taking a short recording with a telemetric heart rate monitor) were evaluated in the preoperative period and then one month and three months after surgery. A post-surgical increase in heart rate variability (spectral, temporal, and nonlinear parameters) was observed, along with an absolute reduction in peak oxygen consumption (VO2peak) and handgrip and knee extensor strength. However, VO2peak and handgrip strength relative to body weight showed an increase after bariatric surgery. Changes in absolute VO2peak were directly related to weight loss after surgery. Likewise, meta-analyses and metaregressions showed that bariatric surgery leads to a significant reduction in the absolute values of VO2max/peak and lower-limb muscle strength in the short-term (up to 12 months post-surgery). In addition, subjects who experienced a higher reduction in body mass index (BMI) after surgery also suffered a higher absolute loss of VO2max/peak and strength. In conclusion, despite the apparent recovery of cardiac autonomic function, bariatric surgery seems to negatively affect cardiorespiratory fitness and lower-limb muscle strength in the short-term. Considering that a low level of these fitness components is associated with a high risk of morbidity and mortality, independent of BMI level, and that even small increases in cardiorespiratory fitness or muscle strength can affect the risk of morbidity and mortality in clinically significant ways, is that the observed reduction in cardiorespiratory fitness and strength after bariatric surgery could be mitigated by prescribing an individualized and supervised physical exercise program as an essential part of the management of these subjects, both before and after surgery. More extended follow-up studies are needed to confirm the adverse effect of BS on physical fitness, as well as to study the consequences of these changes on the health of this population. Combining body composition, cardiorespiratory fitness, muscle strength, and other health outcomes assessments, including larger sample size and multiple time points, could provide a better understanding of the link between weight loss, changes in muscle mass, cardiorespiratory fitness, muscle strength, and health in this population