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Bariatric surgery reduces aerobic exercise capacity

par Zhou, Na ;Faoro, Vitalie ;Forton, Kevin ;Dereppe, Hubert; [et al.]
Référence 29th Great Wall International Congress of Cardiology (GW-ICC)
Publication Non publié, 2018-10-16

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Résumé :

Let’s begin with one story. I had a patient whose BMI was 38, with hypertension and diabetes. She had tried to lose weight several times by dieting and exercise, but she was having trouble maintaining her weight loss. When she stopped the program, her weight fluctuated up and down like a Yo-Yo. She did not feel well and become very quickly breathless during exercise. Why? Because she had more subcutaneous and abdominal fat which led to difficulties breathing. Her heart carried that fat mass like a burden, so she was quickly tired. Last year, her doctor suggested an operation to reduce the size of her stomach. The goal was to lose weight. Three months later, she enthusiastically told me: "I have already lost 20 kg and now I can walk further without breathlessness". Had her physical condition already improved? Yes? No? Does weight loss after surgery equal improved physical condition? In the future, will she still improve? Introduction:Bariatric surgery has become an important treatment option in severe obesity.However, previous studies of aerobic exercise capacity after bariatric surgery weight loss showed contradicting results with either an increased, unchanged or reduced exercise capacity depending on the different protocol.The impact of weight loss after this surgery on exercise capacity remains unclear and lack of long-term outcomes makes guidelines difficult.Aim of the study:The purpose of this study was to determine how much aerobic exercise capacity during cardio-pulmonary exercise test was affected by weight loss in healthy obese women 1 year after bariatric surgery.Methods:We included healthy obese women who underwent body weight measurement, blood sampling and CPET, before and 1 year after bariatric surgery. Patients were tested on a cyclo-ergometer with an incremental increase in the workload until exhaustion. Oxygen uptake (VO2), VCO2 and ventilation were measured continuously via a facial mask.Results-01:Total 40 obese women included, with a mean age of 42 years old and a mean body mass index >40 kg/m2. One year after surgery, the weight loss was around 36 kg and the patients’ dyslipidemia, fasting blood sugar and inflammation factors were markedly reduced (p<0.01). Comparing the CPET’s before and after surgery, we found that the peak VO2 and VO2 at first ventilator threshold (VT1) were reduced after surgery when the VO2 was expressed in absolute value (p<0.01), but not when corrected for(by ?) body weight. In this graph, absolute maximal oxygen uptake and percentage of VT1 reduced but relative maximal oxygen uptake and percentage of VT1 increased. Why? The resultants showed that exercise capacity reduced in unweight baring exercise like pedal the bike (ergometer), because of muscle mass loss after surgery; but if we divide VO2 by patient's body weight, the exercise capacity relative increased, because of lower weight baring (during) exercise just like throw his heavy bag during working or running.There was no difference in maximum VE and VE/VCO2 at VT1. Ventilation and chemosensibility remained unchanged after surgery. Maximum HR had no difference after surgery and O2 pulse increased slightly, so the cardiac adaptation seems to remain unchanged. However, a mild hemodilution may have impact oxygen transport to the muscles.An increased end exercise respiratory exchange ratio (RER), lower max workload with an early VT refers to muscular deconditioning, probably due to loss of lean muscle mass. (Fewer muscles mass produce more lactic acid more quickly during exercise, so RER increase even more in less time.)Conclusions, while bariatric surgery provides weight loss and decreases metabolic and cardio-vascular risks, exercise capacity are reduced with a decreased Peak VO2 and a low ventilator threshold probably related to a muscular deconditioning.This study does not explore that in what proportions the lungs, heart and muscles contribute to limit the physical condition after weight loss? We are currently extender the protocol by adding more measurements such as: DXA, DLCO/DLNO, Exercise Echocardiography and Dynamometer. I hope that next year I will have new results to share with you.