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Energy expenditure climbing Mt. Everest.
K R Westerterp1, B Kayser, F Brouns
1Department of Human Biology, University of Limburg, Maastricht, The Netherlands.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|November 1, 1992
Summary
High altitude expeditions cause weight loss due to reduced energy intake and increased energy expenditure, leading to a negative energy balance. Fat mass loss significantly correlates with this energy deficit.
Area of Science:
- Human Physiology
- Altitude Physiology
- Metabolic Studies
Background:
- Weight loss is common at high altitudes.
- The cause of negative energy balance (anorexia vs. increased energy expenditure) is unclear.
Purpose of the Study:
- To investigate the causes of weight loss at high altitude.
- Simultaneously measure energy intake, energy expenditure, and body composition.
Main Methods:
- Study conducted during Mt. Everest expedition and high-altitude preparation (Alps, hypobaric chamber).
- Measured energy intake via dietary records.
- Measured average daily metabolic rate (ADMR) using doubly labeled water and resting metabolic rate (RMR) via respiratory gas analysis.
- Assessed body composition using body mass, skinfold thickness, and total body water.
Main Results:
- Subjects experienced a negative energy balance (-5.7 MJ/day) at high altitude.
- Average fat mass loss was 1.4 kg, accounting for two-thirds of total weight loss (2.2 kg).
- Energy deficit significantly correlated with fat mass loss (r=0.84, P<0.05).
- Energy intake on Mt. Everest was 9-13% lower than during high-altitude preparation.
Conclusions:
- High altitude induces a negative energy balance primarily driven by reduced energy intake.
- Fat mass loss is a significant component of weight loss at extreme altitudes.
- Both reduced appetite and increased metabolic demands may contribute to energy deficit.