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Energy at High Altitude
  1. NE Hill, Specialist Registrar in Diabetes and Endocrinology1,
  2. MJ Stacey, RAMC, Physician Trainee1 and
  3. Lt Col David Woods, RAMC, Consultant Physician3
  1. 1RAMC and Clinical Research Fellow, Imperial College, London
  2. 3Consultant Physician in Endocrinology and Diabetes Northumbria and Newcastle NHS Trusts, Honorary Clinical Senior Lecturer University of Newcastle, MDHU Northallerton
  1. Dept Endocrinology and Diabetes, Wansbeck General Hospital, Northumberland. NE63 9JJ 01670 564022 01670 523091 DoctorDRWoods{at}aol.com

Abstract

For the military doctor, an understanding of the metabolic effects of high altitude (HA) exposure is highly relevant. This review examines the acute metabolic challenge and subsequent changes in nutritional homeostasis that occur when troops deploy rapidly to HA. Key factors that impact on metabolism include the hypoxic-hypobaric environment, physical exercise and diet. Expected metabolic changes include augmentation of basal metabolic rate (BMR), decreased availability of oxygen in peripheral metabolic tissues, reduction in VO2 max, increased glucose dependency and lactate accumulation during exercise. The metabolic demands of exercise at HA are crucial. Equivalent activity requires greater effort and more energy than it does at sea level. Soldiers working at HA show high energy expenditure and this may exceed energy intake significantly. Energy intake at HA is affected adversely by reduced availability, reduced appetite and changes in endocrine parameters. Energy imbalance and loss of body water result in weight loss, which is extremely common at HA. Loss of fat predominates over loss of fat-free mass. This state resembles starvation and the preferential primary fuel source shifts from carbohydrate towards fat, reducing performance efficiency. However, these adverse effects can be mitigated by increasing energy intake in association with a high carbohydrate ration. Commanders must ensure that individuals are motivated, educated, strongly encouraged and empowered to meet their energy needs in order to maximise mission-effectiveness.

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