Do you know of any studies and/or articles pertaining to the effects of a low body temperature and weight loss? Also, are there any safe ways to increase body temperature?
There is a strong link between thermogenic processes in the body and weight loss/gain. In fact, the whole subject of weight loss is inherently a lot more complicated than we generally give it credit for and involves a wide range of interactions between different hormones, muscle fibre types, neurotransmitters, proteins and other substances that are well beyond the scope of this response to discuss. Though there is a considerable amount of research studies looking at the processes involved, many have been carried out on small mammals, and it seems clear that humans may rely on certain methods and chemical reactions to varying degrees in comparison. Of course, almost all of these interactions are well beyond the scope of the fitness professional to influence, as our main area to target is that of physical activity (in itself a powerful stimulus to body temperature and energy expenditure).
Indeed, thermoregulation itself is an incredibly complex and not entirely clear subject and other variables such as age, gender and menstruation affect it. Again, as these variables are beyond the scope of the fitness professional to alter, we will not discuss them further.
However, to answer your question, low body temperature in general is likely to be something associated with a lack of thyroid activity. Typically, this is something you would associate with weight gain as opposed to weight loss, although less than three percent of people who are obese have an under active thyroid. The thyroid hormones Thyroxine (T4) and Triiodothyroxinine (T3) are chiefly responsible for increasing metabolic rate and would be called into action in the event of a sudden drop, stimulated by the hypothalamus. Signs of an under active thyroid would include cold intolerance, weight gain, decreased appetite, elevated cholesterol and muscle cramps.
However, what research can tell us is that a drop in metabolic rate is commonly seen with people who are on a calorie restrictive regime or performing excessive amounts of moderate intensity aerobic training that tends to encourage the loss of lean body weight (metabolism largely being related to fat free mass), hence leading to a reduction in metabolic rate and therefore intolerance of cold. Several research studies have shown either a decline in the function of the hypothalamus (that directly regulates body temperature) or a drop in T3 levels that would contribute to a reduction in metabolic rate and the associated cold intolerance you mention.
To answer the second part, the reduced body temperature is in this case more of an effect rather than a cause and goes to highlight the problems with rapid weight loss, restrictive calorie regimes and excessive amounts of exercise. Metabolic processes within the body are actually designed to resist increases or decreases in weight outside that of a healthy norm, and this is why we see a catalogue of further health problems in those who adjust their lifestyles in an effort to remain under or overweight. This is compounded by the emotional stress of dieting and weight loss that stimulates cortisol release, which hampers conversion of thyroid hormones (from T4 to T3). This pattern is commonly seen in those with anorexia nervosa and to a lesser degree in those with depression.
To prevent the problems with temperature regulation would require restoring normal thyroid function and diet and may well lead to some weight gain as the body begins to normalize its functions. If this is a client of yours, then these temperature intolerances should be a cause for concern, and I would recommend you discuss a visit to a healthcare professional for help dealing with this and to rule out any other possible causes. The role of the fitness professional in this instance is to encourage the (sometimes reluctant) client to seek further help, rather than to attempt any diagnosis or treatment. For information on some studies you could review, please see the references used below and look into journals on endocrinology, clinical nutrition, metabolism and general medical sources, though remember where the scope of practice of the fitness professional ends.
- Katzeff HL, O'Connell M, Horton ES, Danforth E Jr, Young JB, Landsberg L. (1986) Metabolic studies in human obesity during overnutrition and undernutrition: thermogenic and hormonal responses to norepinephrine. J Metabolism. 1986 Feb;35(2):166-75
- McArdle, Katch & Katch (2001) Exercise Physiology 5th Edition, Lippincott Williams and Wilkins, Baltimore MA.
- Natori Y, Yamaguchi N, Koike S, Aoyama A, Tsuchibuchi S, Kojyo K, Demura R. (1994) Thyroid function in patients with anorexia nervosa and depression. Rinsho Byori. 1994 Dec;42(12):1268-72.
- Prentice AM, Black AE, Coward WA, Davies HL, Goldberg GR, Murgatroyd PR, Ashford J, Sawyer M, Whitehead RG. (1986) High levels of energy expenditure in obese women. Br Med J (Clin Res Ed). 1986 Apr 12;292(6526):983-7.
- Ramazan Sari, Mustafa Kemal Balci, Hasan Altunbas and Umit Karayalcin (2003) The effect of body weight and weight loss on thyroid volume and function in obese women. Clinical Endocrinology Volume 59 Page 258 - August 2003
- Rudolph L. Leibel, M.D., Michael Rosenbaum, M.D., and Jules Hirsch, M.D. (1995) Changes in Energy Expenditure Resulting from Altered Body Weight. N Engl J Med 1995;333(6):399
- Schutz Y, Bessard T, Jequier E. (1987) Exercise and postprandial thermogenesis in obese women before and after weight loss. Am J Clin Nutr. 1987 Jun;45(6):1424-32.
- Spiegelman, Bruce M. and Flier, Jeffrey S. (2001) Obesity and the Regulation of Energy Balance. Cell Volume 104, Issue 4 , 23 February 2001, Pages 531-543
- Vigersky, RA., Andersen, AE., Thompson, RH., and Loriaux, DL., (1977) Hypothalamic dysfunction in secondary amenorrhea associated with simple weight loss. N Engl J Med 297:1141-1145
- Welle SL, Campbell RG. (1986) Decrease in resting metabolic rate during rapid weight loss is reversed by low dose thyroid hormone treatment. J Metabolism. 1986 Apr;35(4):289-91.