Effects of extreme environments on food intake in human subjects

Abstract

fax +31 43 3670976, email M.Westerterp@HB. Unimaas.nl Effects of extreme environments on food intake in human subjects are analysed as behavioural and physiological adaptations to annual and circadian rhythms, temperature and altitude. Effects of the environment on food intake through food availability have direct consequences on energy balance and body weight. Different geographical regions show variations in the composition of dietary foods, i.e. the relative proportions of carbohydrate, protein and fat. In developing countries the annual cycle appears to affect body weight through dependence on food availability. In WestEuropean countries this effect appears to depend on physical activity. Energy and macronutrient intakes appear to follow a circadian pattern, with breakfast being relatively high in carbohydrate and dinner being relatively high in fat. In cold conditions, maintaining an adequate food intake is important in sustaining normal physiological responses to cold. Evidence for a possible coldinduced increase in appetite is poor. A condition influencing level of intake is the palatability of the food. High altitude, i.e. hypobaric hypoxia, appears to reduce appetite, energy intake and body mass, irrespective of acute mountain sickness (AMS). Meal size is reduced and meal frequency increased. Under circumstances of AMS, dissociation between appetite and hunger occurs. Thus, spontaneous adaptation to extreme environments requiring increased energy intake occurs first by adaptation of body weight to a new energy balance. In general, prevention of a negative energy balance occurs by learning with respect to food intake. After return to normal, adjustment of energy intake to the original energy balance occurs with restoration of body weight. Energy balance: Body weight: Hypobaric hypoxia: Macronutrients: Seasonal effectsThe environment: biotic and abiotic factors Ecologically, the environment is characterized by abiotic and biotic factors. The fluctuations, range and interplay of these factors at a certain place determine the habitat of an individual (Bakker et al. 1995). Abiotic factors include temperature, humidity, pressure and day length, also represented by climate, altitude and latitude. Ambient temperature and humidity mainly depend on latitude and a more terrestrial or marine situation, pressure mainly depends on altitude. The abiotic factors day length and rhythmicity depend on latitude.Biotic factors are represented by the other organisms that are present in the same habitat. Their roles range from providing food, shelter or clothing, to being a predator. Distribution and abundance of organisms in a certain habitat are determined by biotic and abiotic factors, as well as by their interplay (Lack, 1954). Adaptation to the environment may take place to a certain extent, and over shorter or longer periods of time, since adaptation can be behavioural, physiological or genetic (Krebs & Davis, 1978;van Rhijn & Westerterp-Plantenga, 1989;Bakker et al. 1995).As such, an ecosystem is dynamic rather than...

Disturbed eating at high altitude: influence of food preferences, acute mountain sickness and satiation hormones

“…Most refer to central neurological effects such as cerebral edema in AMS [37,38]; 83 peripheral, gastrointestinal factors, such as alteration in the secretion of 84 4 neuroendocrine gastrointestinal and pancreatic hormones [1,11,20,32,41] foods [19]. In animal studies hypoxia decreased the 'incentive' to consume food 93 rather than changing 'hunger' or 'appetite', thus shifting the taste spectrum toward 94 'unpalatable' for a given diet [8].…”

“…Most refer to central neurological effects such as cerebral edema in AMS [37,38]; 83 peripheral, gastrointestinal factors, such as alteration in the secretion of 84 Exclusion criteria were: more than three nights above 2500 m in the month preceding 111 study entry; chronic diseases necessitating regular medication such as arterial 112 hypertension, coronary heart disease and pulmonary hypertension; patients with 113 malignancy, transplant patients, patients with clinically significant heart valve disease 114 or with congenital heart or lung disease; lactose intolerance, celiac disease or 115 relevant food allergies or specific food requirements (e.g. vegetarians, Kosher) that 116…”

The ability of habitual exercise to influence appetite and food intake in response to high- and low-energy preloads in man

“…Appetite responses are thus dependent to some extent upon previous energy intake and sensitive to energy deficits induced through differences in intake. However, in contrast, energy deficits induced through increases in exercise do not generally result in short-term increases in hunger ratings or in an elevated energy intake (King et al 1997a;Blundell & King, 1998), and athletes in situations that require sustained performance, such as the Tour de France cycle race, have to learn in respect to food intake in order to prevent negative energy balance (Westerterp-Plantenga, 1999); in addition, becoming sedentary does not down-regulate food intake (Murgatroyd et al 1999). This uncoupling between energy intake and energy expenditure when energy expediture is manipulated by exercise has been reported to persist for several weeks in obese individuals (Woo et al 1982a, b); it has also been reported to occur to a lesser extent when energy expenditure is manipulated by diet .…”

Eating Decisions Based on Alertness Levels After a Single Night of Sleep Manipulation: A Randomized Clinical Trial

“…[19][20][21] External influences include food presentation and environmental conditions. [22][23][24][25][26][27][28][29] External factors can shift awareness away from internal drivers of food intake, potentially causing diminished accordance with health goals and internal signals of satiety. 30 Thus, the act of self-monitoring food intake volume and food type, as well as satiety requires awareness, which is influenced by alertness, which is influenced by sleep.…”