Exercise training and weight loss, not always a happy marriage: single blind exercise trials in females with diverse BMI

Individuals show high variability in body weight responses to exercise training. Expectations and motivation towards effects of exercise on body weight might influence eating behaviour and could conceal regulatory mechanisms. We conducted two single-blind exercise trials (4 weeks (study 1) and 8 weeks (study 2)) with concealed objectives and exclusion of individuals with weight loss intention. Circuit exercise training programs (3 times a week (45-90 min), intensity 50-90% VO2peak, for 4 and 8 weeks) were conducted. 34 females finished the 4 weeks intervention and 36 femalesthe 8 weeks intervention. Overweight/obese (OV/OB) and lean (L) female participants´ weight/body composition responses were assessed and fasting and postprandial appetite hormone levels (PYY, insulin, amylin, leptin, ghrelin) were measured pre and post intervention for understanding potential contribution to individuals’ body weight response to exercise training (study 2). Exercise training in both studies did not lead to a significant reduction of weight/BMI in the participants’ groups, however, lean participants gained muscle mass. Appetite hormones levels were significantly (p<0.05) altered in the OV/OB group affecting fasting (-24%) and postprandial amylin (-14%) levels. Investigation of individuals’ BMI responses using multiple regression analysis revealed that levels of fasting leptin, postprandial amylin increase, and BMI were significant predictors of BMI change explaining about 43% of the variance. In conclusion, tested exercise training did not lead to weight loss in female participants, while a considerable proportion of variance in body weight response to training could be explained by individuals’ appetite hormone levels and BMI.