White or brown, bad or good? We’re not talking about the nutritional value of sliced bread here – we’re talking fat, with a raft of research emerging over the last few years that challenges all our preconceptions.

Up until just a few years ago, it was thought that adults only ever had ‘bad’ fat – the normal white fat that stores calories, meaning you’ll put on weight if you have too much of it.

However, over the last few years we’ve begun to understand that some people have a different kind of fat in their bodies – a fat that might actually help them lose weight by burning calories rather than storing them.

Step forward brown fat. Until recently this was thought to be present only in children, but in 2009 it was discovered that, although it dwindles with age, brown fat is still active in up to 7.5 per cent of adults. While white fat primarily stores energy as triglycerides, brown fat dissipates chemical energy as heat; the more brown fat you have, the more weight you can lose, the faster your metabolism will be and the better your insulin sensitivity, leading to lower risk of type 2 diabetes.

Even better, it’s been shown that energy-storing white fat has the capacity to transform into energy-burning brown-like fat – cue rising numbers of research studies as scientists strive to find more ways to turn white fat into brown fat.

But it may not prove to be a magic bullet to treat obesity, warns Jan Nedergaard, a physiologist at Stockholm University in Sweden. He believes stimulating brown fat is more likely to help keep healthy people from becoming fat, rather than making obese people skinny: “Everybody would like to take a fat person and make him slim, but that demands a high-burning capacity that brown fat probably doesn’t have.”

Nevertheless, with the mindset that prevention is in any case better than cure, we take a look at some of the studies that are starting to shed light on this fascinating topic.