This week I read an article in the New Scientist by Chloe Lambert about ‘good fats’. Now this wasn’t the usual spiel about avocados, nuts and olive oil (although all of these are indeed both good and fats), but rather, it was about ‘brown fat’ and its apparent ability to help us to lose weight.

The existence of brown fat in humans and its impact on our metabolism has only recently been discovered. It appears that these kind of fat cells are able to burn food directly as a mean of producing heat. This is in contrast to the usual process of storing energy from food in white fat cells, which is then only released during activity, such as exercise.

Brown fat cells have a disproportionately high number of mitochondria, and these mitochondria contain the protein thermogenin (or UCP1), which enables them to turn energy directly into heat. In fact, brown fat can produce up to 300 times more heat per gram than any other tissue in the body. Indeed, the primary function of these cells is to regulate the temperature of the body, something which is particularly necessary in certain and mammals and babies who are unable to shiver to stay warm.

In humans, brown fat exists in the neck, shoulders and around the spinal cord and the amount of brown fat varies from person to person.

Brown fat is activated when the body is exposed to cold temperatures and when it is active it increases the rate at which the body burns calories. With regular cold exposure the body is able to adapt, with the brown fat acting as an internal calorie furnace, thus reducing the requirement for the body to shiver to keep warm.

While it may be that the colder you are the better, in terms of ramping up brown fat cell activation, it appears that temperatures of around 17 degrees Celsius are low enough to initiate activation. Lambert cites one trial of Japanese men, who spent two hours a day in a room of 17 degrees for a six week period, resulting in a reported boost in brown fat activity by 50 per cent and a reduction in body fat by five per cent. At the start of the experiment the men burned an average of 108 calories during the two hour period, while by the end they were burning an average of 289 calories. While this doesn’t necessarily indicate that the total calorie burn was as a direct result of the brown fat alone, there is enough evidence from this, and other studies, to suggest that by activating brown fat through cold exposure you may be able to increase the rate of your resting calorie utilisation.

The other positive effect of brown fat activation is that it releases hormones that help to regulate the metabolism of glucose and fatty acids, leading to more stable blood sugar and insulin levels, which could potentially benefit people at risk of diabetes and fatty liver disease.

While brown fat may sound like the answer to all of our weight loss and blood sugar regulating problems, the downside is that we only have a small amount of it in our bodies and, as we age, it diminishes. Moreover, in one study, the boost in brown fat activation experienced by subjects who spent an extended period of time sleeping in a cold room reverted again once the subjects had spent a month sleeping in more temperate conditions. Finally, as Lambert discovered in her own attempts to activate her brown fat cells, we tend to over-compensate when we are cold by eating more, negating the potential positive impact of brown fat activation.

But it’s not all bad news for fat activation and there could be another option. In 2012 a third type of fat was discovered in the human body known as ‘beige fat’. While this type of fat has a different origin to that of brown fat, it does contain the same thermogenin protein, enabling it to burn calories to generate heat. In the case of beige fat, (unlike brown fat), there is potential to create more beige fat, by converting white fat in to beige – again from cold exposure, but also potentially through exercise. In the case of the latter, there is some evidence that the hormone irisin, which is produced when muscles contract, may help stimulate the production of beige fat from white, although this is as yet unconfirmed.

While brown fat may not be the weight loss panacea some hoped for, and while I know exercise and a moderate diet are the key to overall health, this new knowledge may have seen me sneakily opening the window at night and resisting the temptation to turn the heating on in the office. Well. there is no harm in trying, right?

Happy cold showering!