• Dr Sally Norton

How can we help our body burn fat, not store it?

While we all know that ‘brown is best’ when it comes to bread, pasta and rice rather than processed white versions, stripped of fibre and bleached, did you know that your body is made up of both brown and white fat and brown is better than white here too?

This week’s post is packed with the very latest research, so it's a bit of a science lesson. But if you can get to grips with the human biology behind how our body burns and stores fat, you’ll be well on your way to a much more informed approach to weight-loss.

The science bit

There are two types of fat cells (or adipocytes) in the body – brown and white, also known as Brown Adipocyte Tissue (BAT) or White Adipocyte Tissue (WAT). The main difference between the two is that unlike white fat cells which primarily act to store fat, brown fat cells seem to have some positive links to muscle cells and are involved in generating heat from fat, so are found in both hibernating animals and babies who are unable to control their body temperature by shivering.

It wasn’t clear until now whether brown fat persisted into adulthood but a recent study using MRI scanners has further confirmed the presence of brown fat in adults. Another study showed that this adult brown fat was still active – in that it was able to burn energy in cold conditions with the aim of warming us up. The scientific interest (and weight loss interest!) in this lies in the crucial fact that if we can increase the amount of brown fat in our bodies we may be able to burn more energy. Investigators in the field report that 50g of white fat stores more than 300 kilocalories of energy, while 50g of brown fat may BURN up to 300 kilocalories a day. Which would you prefer?!

Slimmer people seem to have more brown fat – with studies of children showing that brown fat levels are lower in fatter kids.

So is it possible to boost brown fat?

Well, as brown fat is important to help warm us up when we are cold, it may not be that surprising then that shivering seems to stimulate the transformation of white into brown fat (helped along by hormones or chemical messengers called irisin and FGF21). Lead researcher, Paul Lee said “White fat transformation into brown fat could also protect animals against diabetes, obesity and fatty liver. Glucose levels are lower in humans with more brown fat.”

Another study has shown that we may be able to change white fat cells into cells closely resembling brown fat by exercise too; yet another reason to keep active! Kristin Stanford, PhD, from Joslin Diabetes Center in Boston, reports: “Our results showed that exercise doesn’t just have beneficial effects on muscle, it also affects fat. It’s clear that when fat gets trained, it becomes browner and more metabolically active. We think there are factors being released into the bloodstream from the healthier fat that are working on other tissues.”

Conversely, however, there is some evidence that our poor diet may be contributing to a reduction in our brown fat, which could be very bad news for our metabolism. A study on mice who were fed a high-fat and sugar diet (equivalent to our increasingly consumed ice-cream, doughnuts and the like) showed that their brown fat underwent changes to make it more like white fat – i.e more of a fat-storing foe than a fat–burning friend. In addition, the researchers linked these changes to the development of a pre-diabetes state.

So what does this all mean?

Once more it seems that our body is much more clever than we give it credit for – and could help us if we work with it rather than against it. A lot more investigation is needed into this exciting new area of obesity research before we know whether we can really manipulate these discoveries to our advantage. However, for the time being, two things seem clear – and fit in with what we know already:

1. Exercise is good – it may boost our brown fat as well as having multiple other benefits. So whilst the calorie burn of exercise may not be that great at the time, if we develop a higher level of brown fat then we increase our fat-burning capability long-term – even when we’re sitting still!

2. Over-eating of food laden with both sugar and fat (i.e processed food not proper food) is bad for yet another reason. It may be producing a very vicious circle – the more rubbish food we eat, the more we destroy our ability to burn it off and the more we increase our tendency to store it instead.

So, there is even more of a reason to make brown your favourite colour!


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