Abstract
BackgroundThe resting metabolic rate (RMR) decrease, observed after an obesity reduction therapy is a determinant of a short-time weight regain. Thus, the objective of this study was to evaluate changes in RMR, and the associated hormonal alterations in obese patients with a very low-calorie ketogenic (VLCK)-diet induced severe body weight (BW) loss.MethodFrom 20 obese patients who lost 20.2 kg of BW after a 4-months VLCK-diet, blood samples and body composition analysis, determined by DXA and MF-Bioimpedance, and RMR by indirect calorimetry, were obtained on four subsequent visits: visit C-1, basal, initial fat mass (FM) and free fat mass (FFM); visit C-2, − 7.2 kg in FM, − 4.3 kg in FFM, maximal ketosis; visit C-3, − 14.4 kg FM, − 4.5 kg FFM, low ketosis; visit C-4, − 16.5 kg FM, − 3.8 kg FFM, no ketosis. Each subject acted as his own control.ResultsDespite the large BW reduction, measured RMR varied from basal visit C-1 to visit C-2, − 1.0%; visit C-3, − 2.4% and visit C-4, − 8.0%, without statistical significance. No metabolic adaptation was observed. The absent reduction in RMR was not due to increased sympathetic tone, as thyroid hormones, catecholamines, and leptin were reduced at any visit from baseline. Under regression analysis FFM, adjusted by levels of ketonic bodies, was the only predictor of the RMR changes (R2 = 0.36; p < 0.001).ConclusionThe rapid and sustained weight and FM loss induced by VLCK-diet in obese subjects did not induce the expected reduction in RMR, probably due to the preservation of lean mass.Trial registrationThis is a follow up study on a published clinical trial.
Highlights
The resting metabolic rate (RMR) decrease, observed after an obesity reduction therapy is a determinant of a short-time weight regain
The absent reduction in RMR was not due to increased sympathetic tone, as thyroid hormones, catecholamines, and leptin were reduced at any visit from baseline
Because very low-calorie ketogenic (VLCK)-diets target body fat mass (FM) with little reduction in fat free mass (FFM) [6], the working hypothesis was that VLCK-diet may induce a minor or null reduction in the RMR, preventing body weight regain
Summary
The resting metabolic rate (RMR) decrease, observed after an obesity reduction therapy is a determinant of a short-time weight regain. It is widely accepted that during periods of energy deficit or restriction (eg., weight-loss diets), the human body tends to diminish energy expenditure by increasing the efficiency in its use and by decreasing the resting metabolic rate (RMR) [18]. This phenomenon of metabolic adaptation to weight reduction is called adaptive thermogenesis, Published research has shown that a very low calorie ketogenic (VLCK)-diet was able to induce a significant weight loss and maintained their efficacy along 2 years [10, 11]. Because VLCK-diets target body fat mass (FM) with little reduction in fat free mass (FFM) [6], the working hypothesis was that VLCK-diet may induce a minor or null reduction in the RMR, preventing body weight regain.
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