What is Thermoregulation in Cold?
Heat production parallels the increase in O2 uptake, the magnitude of which depends on the muscle mass .engaged in slivering or work and the duration of activity. Shivering alone can produce only a four-fold increase above basal rates of heat production. The increase in O2 uptake during shivering thermo genesis is also accompanied by an increase in cardiac output. This increase is due to increase in stroke volume, which is associated with cold-induced peripheral vasoconstriction. The effect of the mechanisms used to protect against heat loss depends on the body surface area in comparison with body mass. The problems may arise in malnourished subjects who have lost both fat mass, as well as, lean body mass. Cold acclimatization can occur in human subjects but it is minimal. An important modifying factor on the thermoregulatory response to cold is the individual's provision of subcutaneous fat, since fat reduces thermal conductance from the core to the body surfaces. Physical fitness has mixed effects; the fittest individuals show more heat production but at the same time, being lean in structure, they lose heat more quickly. Severe losses of body weight in a cold environment complicate the normal physiological responses to cold. Thus, maintaining an adequate intake in cold environment especially under physically active conditions is important. There is a common belief that cold climatic conditions lead to an increased appetite. The evidence for this conclusion is derived from
Changes in body weight; self reported intakes in cold environment at sea level (SL). However, the reported increase in appetite is also associated with changes in other aspects of subject's environment such as increased activity levels, energy expenditure due to thermo genesis, social isolation and modification in the diet. In animals, increased energy expenditure caused by increased thermo genesis due to cold environment is compensated by increased intakes,
In human subjects, increased energy intake requirements do not always trigger an increase intake and appetite immediately. Humans can adapt over a period of time to a high fat diet to make the food energy dense. Now that we are aware of the concept of thennoregulation, let us look at the dietary patterns and the factors affecting food intake of the people residing in cold conditions.