You’re out there freezing (assuming you live in the Northern Hemisphere, here in Australia it’s summer). You’re shivering and actually feel some warmth. It is your muscles burning off energy to warm you up a little bit. But what you don’t know is that at the same time the muscles release irisin. The irisin goes straight to your white fat cells and some are gradually transformed into brown fat cells and activated. And the brown fat cells burn energy rather than storing it relieving the muscles from some shivering activity. Clever don’t you think?
Some puzzling findings
But let’s take a step back. Babies are actually born with a supply of brown fat in the neck region. This is nature’s way of helping infants to keep warm by burning energy when needed. When growing up the brown fat disappears. Or so it was thought. But brown fat has been rediscovered in adulthood in the same neck region. Now a new study suggests that shivering and moderate exercise are equally capable of stimulating the conversion of energy-storing white fat into energy-burning brown fat. Around 50 g of white fat stores more than 300 kilocalories of energy. The same amount of brown fat could burn up to 300 kilocalories a day. Quite a difference. There are a few puzzling findings here. It makes sense for shivering to produce and activate brown fat to help in the process of keeping warm. But the communication between muscle and fat through the irisin hormone to achieve this is quite astonishing. Even more surprising is the fact that exercise can achieve the same result. It is not intuitive since exercise produces heat. It is speculated that muscle contractions during exercising mimic shivering and thus achieve a similar effect. The scientists found that around 10-15 minutes of shivering resulted in equivalent rises in irisin as an hour of moderate exercise. Just be aware that it might take up to a week for the brown fat to be fully developed.
The facts about brown fat
We now know that brown fat is present in most, if not all, adults. Adults with more brown fat are slimmer than those without. When we are cold, we first activate our brown fat because it burns energy and releases heat to protect us. When that energy is insufficient, muscle contracts to produce shivering, thereby generating further heat. The brown fat can provide around 20% of the heat needed, representing a proportion of total energy expenditure sufficient to impact the body’s long-term energy balance. There is excitement in the brown fat field because its energy-burning capacity makes it a potential target to combat obesity. Glucose levels are also lower in humans with more brown fat, potentially providing protection against diabetes.
Your daily treat
So there you have the food connection. As long as you regularly exercise for about an hour or, if you prefer, spend 10-15 minutes in a cold room at 12-14˚C you can have your daily ice cream without putting on weight. I know what I prefer to do.