‘It’s simple – if it jiggles, it’s fat.’ Arnold Schwarzenegger
Your body fat comes in three main types – energy-hoarding white fat (white adipose tissue, or WAT) and an energy-burning brown fat (brown adipose tissue or BAT) and dangerous visceral fat, which can develop around your internal organs when you put on weight.
The colour of brown fat comes from its huge number of energy burning factories, known as mitochondria, within its cells. Brown fat evolved to keep hibernating animals alive during their winter sleep, and to warm infants before they are able to generate heat by shivering. As a newborn baby weighing 8kg you had around 400g of BAT which was mostly found along your upper back, between your shoulder blades and at the back of your neck (that adorable roll of baby fat). By the time you reached adolescence, your BAT had mostly disappeared and, as an adult, your brown fat is mostly confined to the deep regions of your neck where it’s thought to warm the blood travelling through your carotid arteries – this helps to avoid a ‘cold shock’ headache when blood reaches your brain.
The more BAT you have, and the harder your BAT works, the more fat you can burn. Some people inherit greater quantities of BAT and tend to have lower body weight and seem to never put on weight, no matter how much they eat (grrr). Others of us inherit little BAT or retainer very little in adulthood, so we tend to put on weight despite eating healthily. Low levels of BAT also increase the likelihood of developing type 2 diabetes.
The good news is that scientists have found that some white fat cells show a few BAT-like characteristics, and have dubbed this ‘beige’ rather than ‘brown’ BAT. Researchers at the Sahlgrenska Academy at the University of Gothenburg believe there is a way to reactivate your original brown fat to boost the speed at which you burn calories and generate heat. The race is now on to find a drug that enhances the effects of beige BAT or – the Holy Grail of obesity prevention and treatment – converts your WAT to BAT.
Why you don’t want visceral fat
Having a spare tyre around the waist is a visible sign of carrying too much white adipose fat. But what about the fat you can’t see? Visceral fat is also found in your abdomen, but rather than causing a roll, it’s packed around your internal organs such as your heart, liver, kidneys and pancreas. This type of fat is particularly harmful as it releases hormones, free fatty acids and other chemicals that travel direct to your liver. Within the liver, they switch on genes that increase your production of cholesterol, clotting factors, inflammatory substances and glucose. As a result, people who carry too much visceral fat (sometimes known as being apple shaped) have a dramatically increased risk of high blood pressure, raised cholesterol, unwanted blood clots, heart attack, stroke and type 2 diabetes than those with low levels of visceral fat and a smaller waistline.
The best way to measure visceral fat is to simply measure your waist circumference at roughly the widest point. Having a waist measurement over 88 cm (35 inches) in a woman and 102 cm (40 inches) in a man indicates you have an increased risk of heart disease.
Ideally your waist should measure less than 94 cm (37ins) in a man and 80 cm (32ins) in a woman.
Even a modest weight loss of 5% to 10% of your current weight will improve your blood cholesterol level, lower your blood pressure and improve your general health, as much of your initial weight loss comes from visceral fat. If you are overweight and lose just 5-10% of your body fat you could lose around 305 to 40% of your visceral fat.
The following table shows how much weight you would need to lose to achieve a 5% or a 10% weight loss based on your current weight.
|Current weight||A 5% weight loss is:||A 10% weight loss is:|
|12 stones||8.5 lbs||1stone 3 lbs|
|13 stones||9 lbs||1 stone 4 lbs|
|14 stones||10 lbs||1 stone 6 lbs|
|15 stones||10.5 lbs||1 stone 7 lbs|
|16 stones||11 lbs||1 stone 8 lbs|
|17 stones||12 lbs||1 stone 10 lbs|
|18 stones||13 lbs||1stone 11 lbs|
|19 stones||13 lbs||1 stone 13 lbs|
|20 stones||1 stone||2 stones|
Even without weight loss, increasing your level of physical activity can also reduce central obesity and decrease your waist circumference by stimulating loss of visceral fat and altering the way fat is distributed around your body, even if your overall weight is unaffected,
To exercise for weight loss, studies show you need to achieve at least 60 minutes of physical activity (eg brisk walking, dancing, gardening) on most days of the week.