Individual variation in hunger, energy intake and ghrelin responses to acute exercise

Purpose: To characterise the immediate and extended impact of acute exercise on hunger, energy intake and circulating acylated ghrelin concentrations using a large dataset of homogenous experimental trials; and to describe the variation in responses between individuals. Methods: Data from 17 of our group’s experimental crossover trials were aggregated yielding a total sample of 192 young, healthy, males. In these studies, single bouts of moderate to high-intensity aerobic exercise (69 ± 5% VO2 peak; mean ± SD) were completed with detailed participant assessments occurring during and for several hours post-exercise. Mean hunger ratings were determined during (n = 178) and after (n = 118) exercise from visual analogue scales completed at 30 min intervals whilst ad libitum energy intake was measured within the first hour after exercise (n = 60) and at multiple meals (n = 128) during the remainder of trials. Venous concentrations of acylated ghrelin were determined at strategic time points during (n = 118) and after (n = 89) exercise. Results: At group-level, exercise transiently suppressed hunger (P < 0.010; Cohen’s d = 0.77) but did not affect energy intake. Acylated ghrelin was suppressed during exercise (P < 0.001; Cohen’s d = 0.10) and remained significantly lower than control (no exercise) afterwards (P < 0.024; Cohen’s d = 0.61). Between participants, there were notable differences in responses however a large proportion of this spread lay within the boundaries of normal variation associated with biological and technical assessment error. Conclusion: In young men, acute exercise suppresses hunger and circulating acylated ghrelin concentrations with notable diversity between individuals. Care must be taken to distinguish true inter-individual variation from random differences within normal limits. KEY WORDS: Physical activity, Energy balance, Appetite, Variation