Every new year, many of us resolve again to lose that stubborn fat around our hips and bum. It’s dimply, it jiggles and it’s visible to all. We loathe it. But this is not the fat that we should be worried about, not least in terms of our metabolic health. Visceral fat is the fat we ought to be more concerned about.
There are two main types of fat. Subcutaneous fat and visceral fat. Subcutaneous fat, the fat stored directly under the skin, makes up about 80% of our total body fat. A moderate amount is good for your health and can help you live longer.
Visceral fat, on the other hand, is the deadly fat. It is the fat inside your abdomen – inside and around your organs, like liver and kidneys. Visceral fat is more metabolically active than subcutaneous fat. It drives inflammation and causes insulin resistance, which promotes diabetes, cancer, cardiovascular disease, dementia, and aging.
Visceral fat is not always visible from the outside. In 2015, an original research paper, published in the Annals of Internal Medicine, an influential medical journal, concluded that people with high visceral fat and a normal Body Mass Index – in other words, Thin Outside Fat Inside (TOFI) – have a higher mortality risk (much more likely to die) than obese people.
TOFI | Skinny Fat | Normal Weight Obesity
These people appear slim and fit. On the outside, they look normal – even healthy. They are not. They are under-lean (not enough muscle) rather than overweight and tend to carry some weight around the middle (pot-bellied/apple shape). People with large waists but a ‘normal’ weight may suffer the metabolic consequences of high visceral fat: insulin resistance, inflammation, high triglycerides, low good cholesterol, high blood sugar, and high blood pressure.
Professor Jimmy Bell, of Imperial College London, coined the phrase Thin Outside Fat Inside (TOFI). Using MRI body scans, he discovered that it was visceral fat that was driving disease. Researchers in Edinburgh have recently discovered that the origins of visceral fat are genetically different from those of subcutaneous fat.
Body size is misleading, as is BMI (Body Mass Index).
A large waist is therefore strongly associated with an increased risk of type 2 diabetes, cardiovascular disease, and death, even after controlling for BMI. This means that even if you are not overweight, having a large waist may mean that you are at a higher risk of health problems than someone with a trim waist.
The Scales Really Do Lie
Body Mass Index (BMI) is the most common measure of obesity and is a ratio between weight and height. It is imperfect on an individual basis because it cannot distinguish between fat, muscle, and bone, but it can give an accurate assessment of population risk – the portion of the population who are overweight or obese compared to the larger population. Increasingly popular home body fat analysers tell you nothing about the distribution of fat in your body. The problem with BMI is that most athletes, sporting heavy muscles, would have a high BMI when in fact they have low levels of visceral fat.
We now know that people with a normal BMI may well have a large volume of visceral fat. It is estimated that up to 40 percent of the UK population is carrying dangerous levels of visceral fat. I suspect that doctors and the public have become side-tracked by BMI.
That said, if your BMI is over 30, you likely have significant amounts of visceral fat. However, a high waist circumference – resembling an apple shape – means you probably have higher amounts of visceral fat. Use the BMI tool on this page to calculate your BMI. People often assume you need to be really fat to be at risk, but once you hit a BMI of 25, your risk of diabetes, heart disease, and cancer all begin to increase.
Obese people are usually aware of the health risks but those I worry about more are the TOFIs. They may not be aware of the danger that lies inside, and their doctor may not be prompted to consider this because they ‘look OK’.
The main cause of excessive visceral fat is a diet high in refined carbohydrates, processed food, and sugar. Visceral fat is mostly hidden and only accurately detected using medical scans such as MRI or DEXA, but these are costly and not widely available. However, you can easily measure your waist circumference. Better yet, measure your waist to height ratio, which correlates almost perfectly with insulin sensitivity (hence a better predictor of risk). You should be aiming to keep your waist measurement less than half that of your height.
You can now see why your bathroom scales are really not helpful in telling you how healthy or unhealthy you are.
Could you be TOFI?
Do you appear lean but…?
- Have been told you are a ‘borderline diabetic’ or have high blood pressure?
- Have an unhealthy diet full of processed food and sweet treats?
- Carry some extra pounds of weight around your middle?
If you are beginning to wonder how you have managed to get away with it – health wise – you probably haven’t.
- Check your waist circumference. Regardless of your BMI, you should try to lose weight if it is ≥80cm (31.5 inches) for females or ≥ 94cm (37 inches) for males. Tip. Measure across the bellybutton.
- Start reducing your visceral fat by managing your carbohydrate intake. First, eliminate all sugars.
- Get your metabolic blood profile checked, particularly your blood fats, blood glucose, and liver tests. We can check all these and more here.
- Increase your lean muscle mass with resistance training. You do not need a gym or weights. Your own body weight will provide enough resistance.
Remember. You can have a healthy BMI and be metabolically obese, and at risk of developing the Metabolic Syndrome. Step out of the dark. Check your waist circumference and take action.