The influence of low energy availability, with varying protein content, on the inflammatory response to an acute exercise bout.

Abstract

Adequate energy availability is essential to support the body's physiological processes, including the immune system, but currently, there is limited evidence on the effects of brief exposure to low energy availability on the immune system of healthy active people. Therefore, this study's primary aim is to investigate whether an acute period of low energy availability affects immune function in healthy adults. The secondary aim is to verify whether protecting protein intake during the period of caloric restriction, can influence the results, since protein is a macronutrient that can influence several pathways of the immune system. Ten healthy, physically active men aged between 18 and 40 years will participate in eight sessions in the laboratory, being: A) the first session to collect preliminary data; b) the second session to complete familiarization of the exercise test that will be completed in the experimental trials; c) six experimental test sessions, each of which will involve tests conducted pre and post a 4- day experimental diet. The experimental sessions will include: 1- A control condition, with maintenance of energy balance (45kcal/kg FFM/day); 2 - A low energy availability condition, with proportional reduction of all macronutrients(15 kcal/kg FFM/day; LEA) and 3 - A low energy availability test with protected protein intake (LEA-PROT). Each experimental diet will last for five days and will be conducted in a randomized order. On day 1 (baseline tests) the participants will undergo resting metabolic rate (RMR) and body composition assessment. They will also complete a cycling test, comprising a 45 minute fixed load test at 65% of peak power, immediately followed by a wingate test. They will then follow the assigned diet for the next four days, before returning to the lab on day 5 to repeat all test procedures. Blood samples will be collected before, during and after the exercise for the analysis of biomarkers indicative of the immune system, which will include the oxidative response of polymorphonuclear leukocytes, the response of inflammatory cytokines (IFN-³, IL-10, IL-6 and TNF-±) and soluble TNF receptors (sTNFR1 and sTNFR2).