Dietary periodisation to support training outcomes in elite distance athletes (Supernova 1)

The aim of the study is to investigate the effects 3 weeks of adaptation to the low carbohydrate high fat (LCHF diet), on substrate use and subsequent race performance in elite female and male race walkers. Intervention diets will be: 1) control (described separately); 2) LCHF or 3) periodised CHO diets (described below): High-fat low carbohydrate diet (LCHF) : 70-80% fat, 15-25% protein, <50g/d CHO: recently re-emerged dietary strategy to promote increased ability for fat utilisation as a muscle fuel and promoted by Professor Tim Noakes as “the future of endurance performance” Periodised diet involving a careful integration of sessions with high CHO availability (high muscle glycogen, CHO feeding during session), low CHO availability (low pre-exercise glycogen or overnight fasted or delayed refuelling) and well-timed protein intake. With target energy intake isocaloric to LCHF but as follows: CHO 8.5 g/kg body mass, protein 2.1 g/kg body mass, fat 1.2 g/kg body mass. Interventions will last 3 weeks and dietary treatments will commence on the first day of intervention and last until the end. Training will include weekly hill sessions, reps sessions at the track, long walks of 20-45km, and self-selected training sessions based on individual training plans. The diets will be designed by researchers and sports dietitians and all food will be provided for the participants in an individualised fashion (i.e. based on each participant's body weight). Check lists will be available at main meals where a member of the research team will supervise compliance and check that all daily snacks for that day have been consumed. No food or drinks (other than water) will be consumed outside of individual meal plans. Non-energy drinks including black coffee, tea and carbonated water or diet soda can be consumed ad libitum but will require reporting. Subject allocation into dietary treatments will be done based on preference as belief effect is important in exercise nutrition research. Expected training volume per week will be between 120 and 150 km.