Timeline over which compensatory mechanisms are activated during weight loss with a very-low-calorie diet
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Background: Diet-induced weight loss (WL) activates several compensatory mechanisms, both at the level of energy intake (EI) and energy expenditure (EE), which increases the risk of relapse. Unfortunately little is known regarding when these mechanisms are activated and how they respond with progressive WL. Purpose: To assess the timeline over which compensatory mechanisms are activated during WL with a very-low-calorie diet (VLCD). Material & methods: Twelve healthy obese men and women underwent an 8-week VLCD. Body weight and composition, resting energy expenditure (REE), exercise efficiency (at 10, 25 and 50 W) and subjective feelings of appetite (in fasting and for 2.5 h after a meal) were measured at baseline, day 3, after 1 week, when each individual participant lost 5 % and 10 % of his/her baseline weight and at the end of the intervention. Results: Significant WL was seen at day 3 and got stronger with progressive WL. REE was significantly reduced at 5 % WL and remain stable until end of study. A significant increase in exercise efficiency at 10 W was only seen at end of VLCD (average WL of 18.4±2.3 kg). No significant changes in subjective feelings of appetite were observed, but there was a tendency (P=0.058) for an increase in subjective feelings of hunger in fasting at day 3. Conclusion: Losing weight with a VLCD (ketogenic diet) leads to a significant reduction in REE from 5 % WL with no changes afterwards, while an increase in exercise efficiency at 10 W is only seen at the end of the intervention. Subjective feelings of appetite do not seem to change significantly over time, even though a slight increase in fasting hunger may be seen at day 3. Relevance The assessment of the timeline over which compensatory mechanisms, both at the level of EI and EE, are activated with WL is extremely important to health professionals working within obesity management. This knowledge will provide health professional with the understanding of when compensatory mechanisms start to be activated and also, potentially, when a plateau is reached. This information is very valuable since it can be used to try to help obese people to lose weight and maintain it in the long term.