Lean People Turn Up The Heat, Obese People InsulateTuesday, April 6, 2010
Humans, like all mammals, face the challenge of maintaining our body’s core temperature (at around 37 degrees Celsius or 98 degrees Farenheit) despite changes in ambient temperature. This maintenance of temperature comes at a caloric cost – indeed, a considerable proportion of the calories we burn each day are used solely for regulating our body’s temperature.
When ambient temperatures drop, our bodies can respond with two mechanisms to maintain body temperature: burn more calories to produce more heat (adaptive thermogenesis) and/or reduce blood circulation to peripheral tissues (like arms, legs and skin) to reduce heat losses (insulation).
Now Sander Wijers and colleagues from the University of Maastricht in the Netherlands, in a paper just published in OBESITY, addressed the question whether obese subjects differ from lean individuals in their response to cold exposure .
In their experiment, they exposed 10 lean and 10 obese subjects for 48 h to mild cold (16 degrees Celsius or 61 degrees Farenheit) in a respiration chamber.
They found that the lean but not the obese subjects effectively increased their mean daytime energy expenditure (by burning more calories). Lean subjects also showed a larger decrease in distal skin temperatures, whereas obese subjects decreased proximal skin temperatures more prominently
From these findings the researchers conclude that while lean individuals have to burn calories to protect their body temperature, most obese individuals can effectively cut losses by depending on their better insulation (offered by the layer of body fat).
This finding may have interesting public health implications. The recent discovery of brown adipose tissue, which is known to burn more calories with cold exposure, has led to the speculation that reducing ambient temperatures may help people burn more calories and thereby help reduce obesity rates.
However, the present study suggests that although lower ambient temperatures may help lean people burn more calories, obese individuals will simply cut losses and make good use of their insulation.
This would mean that even if mild cold exposure may be a measure to prevent increases in body weight in lean people, it is highly unlikely to do much to help drop pounds in those who already have excess weight.