Nutrition and the responses to extreme environments

Area of Science:

• Environmental Physiology
• Human Metabolism
• Nutritional Science

Background:

• Energy requirements are influenced by environmental conditions, including temperature.
• Previous research on thermal stress and metabolic rate has yielded varied results.
• Understanding human physiological responses to extreme environments is crucial for health and performance.

Purpose of the Study:

• To investigate the impact of cold and hot environments on human energy requirements.
• To clarify the factors contributing to increased metabolic rate in extreme temperatures.
• To assess the role of diet composition in thermoregulation and adaptation.

Main Methods:

• Analysis of existing studies on human metabolic rates in different thermal environments.
• Review of physiological data related to heat transport, ventilation, heart rate, and metabolic adjustments.
• Evaluation of evidence regarding dietary modifications for heat/cold tolerance and altitude exposure.

Main Results:

• Cold environments minimally increase metabolic rate (2-5%) primarily due to clothing, with body weight and activity being key factors.
• Discrepancies in hot environment studies are linked to heat protection levels; extreme heat increases energy demands via physiological strain.
• No evidence supports macronutrient modification for heat/cold adaptation; high-carbohydrate diets show promise for high-altitude tolerance.

Conclusions:

• Energy expenditure in cold is mainly determined by body weight and activity, with minimal impact from clothing.
• Extreme heat significantly elevates human energy requirements due to increased physiological workload and heat stress.
• Dietary interventions are not proven for thermoregulation, but carbohydrate intake may benefit high-altitude performance.