Energy, substrate and protein metabolism in morbid obesity before, during and after massive weight loss

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Abstract
OBJECTIVE: To investigate the effect of surgically induced weight loss on energy, substrate and protein metabolism of morbidly obese patients. DESIGN: A prospective, clinical intervention study of morbidly obese patients before and after surgical treatment. SUBJECTS: Eight morbidly obese patients (BMI 47.88±7.03). METHODS: Total energy expenditure (TEE; doubly labeled water method), sleeping metabolic rate (SMR; respiration chamber), body composition (deuterium oxide component of doubly labeled water), substrate metabolism (48 h dietary records, 48 h urine collection and gaseous exchange in the respiration chamber) and whole body protein turnover (primed-continuous infusion of L-[1-13C]-leucine) were measured before, 3 and 12 months after vertical banded gastroplasty (VBG). RESULTS: The TEE decreased as a result of a decreased SMR (64%) and non-SMR (36%; P=0.001). SMR as a function of fat-free mass (FFM) decreased after weight loss (PP<0.05), although 3 months after VBG protein oxidation did not decrease enough to prevent loss of FFM. The energy used for protein turnover was approximately 24% of SMR and did not change after weight loss. CONCLUSIONS: Compensatory processes that oppose weight loss of morbidly obese patients exist, as demonstrated by the disproportional reduction of SMR, and a low PAI. Protein turnover is not a major contributor to the disproportional reduction of SMR.