24-h passive heat and cold exposures did not modify energy intake and appetite but strongly modify food reward.

Effects of acute thermal exposures on appetite appear hypothetical in reason of very heterogeneous methodologies. The aim of this study was therefore to clearly define the effects of passive 24-h cold (16°C) and heat (32°C) exposures on appetitive responses compared to a thermo neutral condition (24°C). Twenty-three healthy, young, and active male participants realised three sessions (from 1 pm) in a laboratory conceived like an apartment dressed with the same outfit (Clo=1). Three meals composed of three or four cold or warm dishes were served ad libitum to assess energy intake (EI). Leeds Food Preference Questionnaires were used before each meal to assess food reward. Subjective appetite was regularly assessed and levels of appetitive hormones (acylated ghrelin, GLP-1, leptin, and PYY) were assessed before and after the last meal (lunch). Contrary to the literature, total EI was not modified by cold or heat exposure (p=0.120). Accordingly, hunger scores (p=0.554) were not altered. Levels of acylated ghrelin and leptin were marginally higher during the 16 (p=0.032) and 32°C (p<0.023) sessions, respectively. Interestingly, implicit wanting for cold and low-fat foods at 32°C and for warm and high-fat foods at 16°C were increased during the whole exposure (p < 0.024). Moreover, cold entrées were more consumed at 32 °C (p<0.062) and warm main dishes more consumed at 16°C (p<0.025). Thus, passive cold and hot exposures had limited effects on appetite and it seems that offering some choice based on food temperature may help individuals to express their specific food preferences and maintain EI.

Evaluation of the efficacy of a light ration adapted to cold weather during a 20-day expedition in Greenland.

INTRODUCTION: Limiting body mass loss during military expeditions/training in the cold by providing rations containing easy-to-use, highly palatable, and familiar foods is feasible, but the bulk/weight is too high to be realistically used in a military context. We carried out an analysis of lighter rations adapted to cold weather (1,011 g, 15.7 MJ/3750 kcal) during a 20-day expedition in Greenland. METHODS: Ten French soldiers daily reported all foods and beverages consumed, the reasons they did not consume certain foods, the palatability of each consumed food, the timing of intake, and the sensation of hunger using a diary. RESULTS: Although energy intake increased in the 3rd week (vs 1st week; p = 0.015), it was insufficient to prevent the loss of body mass (-4.2 ± 1.9 kg, p = 0.002). More extensive analyses showed that 1) energy intake increased only during dinner (p = 0.024) and that hunger levels continued to increase before dinner (p = 0.029), 2) palatability increased during the 3rd week (vs 1st week) especially for savory day foods (p< 0.001), and 3) lack of hunger and lack of appeal (33 % each) were the main reasons for not consuming certain items. CONCLUSION: Soldiers placed in total autonomy during a 20-day expedition in the cold and provided rations that were slightly undersized but adapted for cold conditions, surprisingly, remained picky, leading to large losses of body mass. Our results suggest a margin for improvement to stimulate spontaneous food intake. For example, more energy-dense and savory foods during the day and the replacement of certain disliked items.