Besides high-energy food intake and a sedentary lifestyle, a factor that may be playing a role in expanding waistlines of people is our over-dependence on technologies to control ambient temperature. By controlling the ambient temperature for comfort, we may be minimising the extent to which we would otherwise be using our body’s energy to control body temperature.
Reducing the intake of food and increasing physical activity levels have been proven strategies to reduce weight. But long-term adherence is difficult.
“Regular exposure to mild cold may provide a healthy and sustainable alternative strategy for increasing energy expenditure,” notes a paper published on January 23 in the Trends in Endocrinology and Metabolism journal. “In parallel to physical exercise, one should promote temperature training as part of a healthy lifestyle.”
Similar to cold exposure, exposure to hot temperature also results in increased usage of body energy. “During rest and normal daily life, it is to be expected that extreme high temperatures will raise the energy expenditure,” Wouter van Marken Lichtenbelt from Maastricht University Medical Centre, The Netherlands and the lead author of the study said in an email to this Correspondent.
Though producing heat through shivering is by expending energy, shivering thermogenesis is more for short-term protection. In contrast, nonshivering thermogenesis (NST) is a cold-induced increase in heat production that does not hamper co-ordinated movements. It instead occurs in the heat-generating, calorie burning brown fat (brown adipose tissue); some studies have attributed it to skeletal muscles.
According to Prof. Lichtenbelt, in most young and middle-aged people, the increase in non-shivering thermogenesis varies from a small percentage to 30 per cent in response to mild cold exposure.
In contrast to a study published last year in the Journal of Clinical Investigation in which researchers found a reduction in brown fat when people were exposed to 17 degree C for two hours a day for six weeks, Lichtenbelt and his team found an increase.
The authors found cold acclimatisation occurred when 16 subjects were exposed to 15 degree C for six hours a day for 10 days.
The authors state that brown fat would increase and non-shivering thermogenesis would in turn increase even at a bit warmer temperature of 18-19 degree C. But the time taken to achieve similar results would take longer.
Answering a question whether cold exposure in any way changes the basic metabolism rate in an individual, he noted: “Yes, your resting metabolic rate goes up, but your cold-induced metabolism goes up to a larger extent.” As the metabolic rate goes up, the energy expenditure goes up as well. As a result, people are less likely to become obese. Compelling our bodies to spend more energy to maintain thermal balance through cold exposure may appear to be one of the ways to remain healthy. But many large-scale studies need to be undertaken to evaluate the correlation of cold acclimatisation and its beneficial effects before it is advanced as a public health measure akin to exercising.
“We still need long-term studies,” he noted. “The article was meant to indicate that from a physiological point of view there are several lines of evidence that temperature variations and mild cold can be healthy.”
But as he states in his paper, cold exposure should be complemented with healthy lifestyles like exercising and reduced intake of high-calorie food.