Investigating the Early Markers of Weight Loss

The study will include 30 women randomized in two distinct groups: G1: Slow weight loss and G2: Rapid weight loss . The total duration of the program will be different for each group, being over 20 and 10 weeks for G1 and G2, respectively, in attempt to match the groups on amount of weight loss (approximately 20 pounds per subject). Participants who meet the inclusion criteria will be randomized to rapid or slow weight loss groups. The energy deprivation of the rapid and slow weight loss will be in -1000 kcal/day and -500 kcal/day, respectively. Calculated based on the baseline resting energy expenditure (REE; determined by indirect calorimetry) and their physical activity level measured for one week. The diet macronutrient composition will be personalized for each participant based on the results of 2-day energy intake at preliminary session, measured with food items selected from a validated food menu. Individuals will be instructed to maintain the level of energy restriction and macronutrient composition during the diet period, however they will be able to do food exchanges, based on the Canadian Diabetes Association system. It will be measured participant's body weight, body compositions, appetite sensations, resting energy expenditure, energy intake, palatability, olfactory performance, food reward, food reinforcement and impulsivity. Participants will have 7 sessions in total: 1 preliminary, baseline, 7 days of intervention, 3 follow ups and final assessment.