Weight Loss and Hunger

Weight loss reduces all components of the energy budget, i.e. resting energy expenditure (EE), the thermic effect of feeding and the energy cost of physical activities. The corollary of this observation is that to achieve energy balance at a lowered body weight (if EE is not increased through purposeful physical activity), energy intake (EI) needs to be kept at this lowered level of EE. While the math of the equation is simple, the operationalization has proven to be quite different. In fact, a dominant feature of weight loss is that it produces increases in hunger that appear within the first days, persist into weight loss and for at least a year after the intervention. As such, identifying strategies that abate changes in hunger and facilitate post-weight loss appetite control should be viewed as a central tenant of obesity interventions. However, data points to the possibility that it may well be the reduction in EI needed to produce weight loss that actually increases hunger. If this were to be the case, then forcing lower EI after weight loss likely exacerbates the state of increased hunger, paving the way for weight rebound. If there is somewhat a set value of EI for each individual, then current dietary strategies aimed at tailoring a food landscape conducive of reduced hunger with reduced EI needed to sustain weight loss, are destined to fail. Primary hypotheses- The increase of EI to pre-weight loss values will significantly attenuate weight loss induced increases in hunger. Secondary hypothesis- The increase of EI to pre-weight loss values will significantly attenuate weight loss induced metabolic adaptations (Greater than Predicted decreased in EE). The increase of EI to pre-weight loss will significantly improve post weight loss ghrelin, PYY and GLP-1 responses. Research plan- Fifty individuals living with obesity (25 men and 25 women BMI ≥ 30 kg/m2) will undergo a 20-week weight-loss intervention. After weight loss they will be randomly assigned to a 1-month experimental condition comprising of either : 1) a weight maintenance diet; or to 2) an increase of EI to pre-weight loss levels combined with increased exercise to maintain energy balance. A detailed investigation of energy balance variables will be conducted at all three time points. Relevance- Discovery drives paradigm changes, which hold the promise of catalyzing innovation in treatment. The clinical impact of a setpoint EI is that it would inform more tailored personalized dietary intervention based on one's individual pre-weight loss EI rather than post-weight loss outcomes, which is the current standard of care for maintenance of weight loss. In other words, it could inform the precise corrections in EE (from physical activity) needed to not exacerbate appetite control, and to likely favour healthier weights.