Simple nouns can be misleading. There is the “actor†who has spent years in repertory and now performs Shakespeare in the West End and there is the “actor†who last week was trying to master year 10 trigonometry and this week landed the role of “Dougie†in a forgettable soap; both “actors†but very different beasts. Then there is the “salad†you get served up in plastic in a fast food restaurant and the “salad†lovingly crafted by your partner complete with home-made dressing and garden-picked veggies. Two things can go by the same name and yet be totally different in nature. Just so is white fat a very different thing to brown fat in your body and a new study has found how to boost those brown fat levels.
The main function of brown fat is to generate heat which is why in humans it is at its highest in babies. In the animal kingdom it is at high levels in hibernating animals. Where 50g of white fat stores around 300 kilojoules, brown fat burns around 300 kilojoules daily.
We already know that cold temperatures stimulate brown fat and that exercise can also turn white fat into brown fat. However, this study has made a new discovery.
The research involved exposing volunteers to increasing levels of cold. The subjects experienced temperatures from -7 degrees Celsius down to -11 degrees Celsius until it made them shiver. Most subjects started to shiver around -9 degrees Celsius. The researchers wanted to see what hormones are released by cold temperatures and shivering and how they may relate to fat deposits.
Blood samples were drawn throughout the experiment and special instruments detected when the subjects began to shiver.
The results showed that shivering muscles release a hormone called irisin. They also found that brown fat exposed to cold releases a hormone called FGF21. Irisin was discovered by Harvard researchers in 2012 and has been shown to turn white fat cells into brown fat cells. The researchers found that subjects released the same amount of irisin after 10-15 minutes of shivering as they do after one hour on an exercise bike.
The researchers theorise that exercise may be mimicking shivering and the effect is turn white fat into the energy burning brown fat that you want. Is that exciting news? It’s giving me shivers and is exceptional news for the athletes in Sochi…they are getting double the benefit.
