ICECAP: Intermittent versus Continuous Energy Restriction Compared in an Athlete Population

This study will comprise of 3 phases: [1] Pre-energy restriction phase, [2] Energy restriction phase, and [3] Post-energy restriction phase. The Pre-energy restriction phase consists of training participants how to use a mobile application for self-monitoring energy and macronutrient intake during a diet log over 1 week. The diet log will be followed by a 4-week period of weight maintenance. Weight maintenance energy requirements will be estimated for each participant using a sequential series of prediction equations that take into consideration age, sex, body size and physical activity level, as described previously (1). Participants will be instructed to contact the lead researcher (JP) if weight is gained or lost consecutively for 3 days, in which case they will be provided with an amended diet prescription to maintain weight stability. During the Energy restriction phase all participants will be randomised to continuous or intermittent energy restriction interventions. The continuous intervention consists of 12 weeks on a diet eliciting a weekly weight loss of 0.7% of the participant's Pre-energy restriction body weight in line with previous findings (2). The intermittent intervention consists of 12 weeks of total energy restriction administered as 3 weeks of energy restriction on the diet described above, followed by 1-week of energy balance on a diet at 100% of maintenance energy requirements, for a total of 15 weeks. Both interventions will be administered by the lead researcher (JP). If the participant achieves a weekly weight loss of < 0.5% of their Pre-energy restriction body weight, then the daily energy intake of the prescribed diet will be reduced by 5% to help keep participants at approximately the same rate of weight loss throughout the study, in keeping with a method commonly used by athletes to amend energy intake during weight loss interventions. Adherence to the allocated intervention will be evaluated via weekly review of participant food diaries and partially by success in reaching weekly weight loss targets. In the Post-energy restriction phase participants will complete a 6-month free-living period during which time there will not be any scheduled dietary support from the research team. The macronutrient prescription in energy restriction and energy balance will be based on previous nutritional recommendations for athletes undergoing weight loss interventions (3): protein intake of 2.3 g/kg of body weight, dietary fat intake of 20% of energy intake, with remaining energy intake allocated to carbohydrate to support training demands. (1) Gerrior S, Juan W, Peter B. An Easy Approach to Calculating Estimated Energy Requirements. . Preventing Chronic Disease. 2006;3(4). (2) Garthe I, Raastad T, Refsnes PE, Koivisto A, Sundgot-Borgen J. Effect of two different weight-loss rates on body composition and strength and power-related performance in elite athletes. International journal of sport nutrition and exercise metabolism. 2011;21(2):97-104. (3) Helms ER, Aragon AA, Fitschen PJ. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. Journal of the International Society of Sports Nutrition. 2014;11:20.