Just being thin doesn’t mean you’re not carrying around excess fat

British researchers have found that it is possible to be a healthy weight for your height, but still have unhealthy levels of fat in your body. And the worrying thing is that internal fat is particularly dangerous and causes serious health problems. Even scarier is knowing that because this fat can’t be seen, you may not be aware you’re at risk until it’s too late. Here’s what you need to know about hidden fat:

How is it possible to be thin on the outside and fat inside?
Fat doesn’t just get stored under your skin – it also builds up inside your body. This kind of fat is called visceral fat, while external fat is called subcutaneous. Visceral fat can be wrapped around organs like your heart, liver, kidneys and pancreas or streaked through underused muscles, although it’s mostly found in your abdomen. Just as it’s possible to be slim and have this hidden fat, there are some people who may be overweight but fit, and have less dangerous visceral fat than their skinny friends.

How does internal fat build up? The biggest risk factor appears to be lack of exercise, according to the researchers who studied visceral fat. They found that people who exercise regularly tend to have lower levels of internal fat than couch potatoes, even slim ones.

Other risk factors include:

• Your genes.
• Your body shape (apple-shaped women are more likely to store internal fat than pear-shaped ones).
• Crash dieting. When you go on a diet only a small amount of fat is lost from your internal stores, but when you gain weight, the first place it goes to is your abdomen.
• Smoking.
• Drinking alcohol.
• The kind of fats you eat. If you eat mostly saturated and trans fats, you are likely to have more visceral fat than someone of the same height and weight who eats mostly unsaturated fats.
• Long-term stress. This triggers the release of high levels of cortisol, a hormone that seems to encourage fat storage in the abdomen.
• Menopause. When oestrogen levels drop, fat gets stored around your middle.

Why is internal fat so dangerous?
Body fat is more than just slabs of lard. It’s like another organ – it has blood vessels and releases hormones and proteins that affect your metabolism. Body fat can have an impact on all sorts of things, including your fertility, mood, immune system and ability to think clearly. Internal fat appears to secrete more chemicals. Plus fat being wrapped around major organs can lead to conditions like heart disease and high blood pressure. It also seems to affect glucose levels, possibly triggering type 2 diabetes.

How do I know if I've got too much internal fat? It’s tricky. A specific MRI scan is the only certain way. Some body-fat monitors (used by gyms) may be able to give you an idea, and if you look thin, but have a higher than expected fat reading, that could be a clue.

A quick test to asses your risk
The more times you agree with the statements below, the greater your chance of having high levels of visceral fat.

• You’re completely inactive or exercise for less than 30 minutes a day.
• You’re apple-shaped (you store your fat around your stomach not bottom and hips).
• Your waist is more than 80cm (for women).
• You have been a crash or yo-yo dieter.
• You smoke.
• You drink more than one unit of alcohol a day.
• You eat mostly saturated fats (ie red meat, butter, cheese etc) rather than unsaturated fats (ie vegetable oils).
• You often feel stressed.

How can I get rid of internal fat?
Exercise is the best way, according to the British study. The researchers got 20 volunteers to do cardiovascular exercise for an hour, three times a week, and after six months they’d lost around 60% of their hidden fat. They say you should avoid very strenuous exercise and concentrate instead on doing at least half an hour’s moderate aerobic activity, such as walking, every day.

Other things that may help

• Changing your eating habits in an effort to lose weight. This doesn’t mean going on a diet you can only stick to for a short while – it means replacing unhealthy foods with healthy, low-fat ones and creating an eating plan you can follow for the rest of your life. If you lose lots of weight only to put it back on, all you’re likely to be doing is increasing your levels of internal fat.
• Increasing the amount of beans and pulses you eat. Early results from one English study suggest that they somehow cause fatty tissue to be redistributed around the body, rather than just building up around the stomach.
• In conjunction with exercise and healthy eating, cutting right down on alcohol, quitting smoking and learning to control your stress levels with techniques such as meditation may also help.

What the scientists found
A team of British researchers, led by Professor Jimmy Bell at London’s Hammersmith Hospital, took MRI scans of over 400 women and found 40% of them had high internal fat levels. These included a 33-year-old actress, who was 1.75m and 57kg, giving her a BMI of 19.9 (within the healthy range of 18.5 to 25). A scan showed she had three litres of internal fat – that’s three times the healthy level of one litre. The woman, who didn’t want to be named, was shocked by the result but admitted she didn’t eat healthily and never exercised.

Did you know...?
High levels of hidden fat may be rife in the fashion industry. If those incredibly thin models don’t exercise, go from one fad diet to the next and puff away on fags, chances are they could be carrying around more internal fat than you!