Low Carbohydrate Availability, Not Energy Availability, Alters The Immune Response To Exercise In Elite Race-walkers

Abstract

PURPOSE: To compare the effects of a ketogenic low carbohydrate (CHO) high fat (LCHF) diet, and a low energy availability (LEA) diet, on innate immune response during a short-term training intervention in endurance athletes. METHODS: Twenty elite male race walkers completed one of three 5-7 day diet/training phases in a parallel groups design. During the initial 5 day Harmonization phase, all athletes consumed a high energy availability (HEA) diet equating to 40 kcal.kg-1fat free mass (FFM).day-1. Athletes were then assigned to either a HEA (n=6), LCHF (<50 g CHO.day-1 and isocaloric to HEA, n=7) or a LEA diet (15 kcal.kg-1FFM.day-1, n=7) for the 7 day Intervention phase. Subsequently, all athletes were placed back on a HEA diet for a further 5 days (Re-feed phase). On day 5 of each phase, athletes completed a 25 km hybrid laboratory-field race walk protocol at ~75% VO2max. Venous blood samples were collected pre-, post-, and 1 h post-exercise and analyzed for serum ferritin, white blood cell counts, cortisol and blood glucose concentration. RESULTS: Serum ferritin decreased from Harmonization to Re-feed in all 3 groups (HEA: 30%, 20-40% (mean change, 95% CI); LCHF: 38%, 22-54%; LEA: 40%, 17-63%, p<0.01), however, the magnitude of decrease was similar between groups.During the Intervention phase, the LCHF had a larger post-exercise increase in total white blood cells (67%, 61-72%), neutrophils (77%, 71-82%), monocytes (49%, 32-65%) and lymphocytes (41%, 31-51%) than both HEA (p<0.001) and LEA (p<0.001). Similarly, a small increase in cortisol (14%, -10-39%) and a decrease in blood glucose levels (46%, 18-74%) were evident during the post-exercise period during LCHF, which was significantly different to, and occurred in the opposite direction to changes seen in HEA and LEA. No differences in any marker measured occurred between HEA and LEA, or between the Harmonization and Re-feed phases. CONCLUSIONS: Adherence to a ketogenic LCHF diet for 5 days resulted in transient perturbations to the immune response to exercise, however, the LEA intervention did not influence immune markers. It appears that the acute restriction of CHO, rather than energy intake, has a more detrimental impact on the immune response to exercise in elite endurance athletes.