Understanding Hypothermia

Understanding Hypothermia

Background to Hypothermia and what the body is trying to achieve


Before getting too far into the nitty gritty of symptoms and treating hypothermia, we’ll start by trying to understand the broader concept what happens to the body when it gets cold; too cold. The word itself is broken down into two important parts; ‘hypo’ means low - as for many medical conditions - and ‘therm’ meaning temperature.


The Core

The main functions of the body – the things that keep us alive – are the internal organs; the heart, lungs, liver etc, including the brain, and without these organs functioning properly, you die. It’s that simple. The main organs are contained in the trunk or torso of the body, which is more correctly known as the ‘core’, and the body is efficient at keeping the core at the optimum temperature of 37 degrees Celsius (98.6 Fahrenheit). To maintain that temperature takes energy in the form of food, which is literally burned (aka metabolism) by the body to keep us warm. It is the muscles and internal organs that generate our heat, and muscles at exercise generate even more heat.

Calorie Intake
In normal lowland conditions men typically requires 2,500 calories a day (women approx 2,000) just to keep going. Combine the base calorie requirement with a strenuous day in the hills and there’s a clear requirement to eat more, especially if the weather is likely to be cold and wet. Many people watch what they eat, in terms of calories, with low calorie food being preferable for a normal day. However, in the hills the opposite is true as we need lots of calories to keep ourselves warm and walking efficiently.

Some people in the group many need help in understanding the different types of food and calorie content, and advice about what’s best to take.  

Insufficient calorie intake, combined with vigorous exercise leading to exhaustion, is a factor making someone particularly susceptible to hypothermia.

Heat Loss

The body loses heat by the following methods: 

  • Conduction – loss of heat via contact with something colder than the body, for example wet clothes or the ground if lying down. Water conducts heat away from the body 25 times faster than air. If you sit on the ground you will lose heat through conduction

  • Radiation – loss of heat to the still cold air around you

  • Convection – for the purposes of hypothermia, this is wind chill

  • Evaporation – when sweat evaporates, it cools you down. 


The main causes of hypothermia are;

  • rain, or immersion in water in a cold environment

  • poor clothing - unsuitable or leaky waterproof

  • insufficient calorie intake

  • exhaustion

  • lack of appropriate fitness for chosen route

  • dehydration

Medical Factors

Combine the above with medical factors, such as having or recovering from a cold, hypoglycaemia (low blood sugar), or hypothyroidism (aka underactive thyroid gland), or any other condition that affects judgement, and the risk increases. Those who have little knowledge of hypothermia are more likely to succumb to it, and older people are more likely to die from it.