Effects of fasting or a vegetarian diet on subjective ratings of appetite and mood during strenuous physical activity

Abstract

Thirty-four subjects participating in "fasting marches" at a health spa were studied during three days of hiking 14-27 km daily and the combined effects of either fasting (n=10) or a hypocaloric lactovegetarian diet (n=20). Hunger, satiety, tiredness, irritability and contentedness, assessed by visual analogue scales, and the energy intake (fasting fixed to 1.1 MJ, 253 kcal/day, lactovegetarians mean 4.8 MJ, 1147 kcal/day) assessed by dietary recall were analysed. Lactovegetarians on their hypocaloric diet experienced more hunger before meals than fasters but a similar degree of tiredness. The combination of exercise and a hypocaloric diet, probably resulting in varying degrees of ketonaemia, seems to lead to responses which can be explained by a combination of psychological and physiological reactions. Fasters, although less hungry than lactovegetarians, complied equally well with the endurance program, but displayed lower mood. Key words: appetite, exercise, fasting, hunger, mood