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Normal weight obesity - Can you look slim, have a normal body weight and yet still be fat?

Published:Tuesday | February 2, 2010 | 12:00 AM

A recent report from the Mayo Clinic says yes and suggests hidden fat in your body can increase your risk of serious diseases even when your bathroom scales scale say you are OK. The Mayo researchers call this problem normal weight obesity and estimate that more than 30 million Americans fall into that group.

In a study of more than 6,000 Americans with normal body size and body mass index, the doctors showed that people do not have to be overweight to have excess body fat. Their bodies are normal in weight but have too much fat and not enough muscle. Other researchers have used MRI scans of the body to demonstrate that many normal weight or even underweight individuals have excess and dangerous deposits of body fat, especially in and around their internal organs.

In my own medical practice, I regularly see people who are convinced that they have no weight or excess fat that they need to lose. In a short while, with simple changes in nutrition and lifestyle, they are amazed to see the transformation in their body's shape and size.

DANGERS OF HIDDEN FAT

According to the Mayo Clinic study's findings, a high body fat among normal-weight men and women was associated with an almost 400 per cent increase in the risk for what is called the metabolic syndrome - elevated blood sugar, blood pressure, blood cholesterol and triglycerides in association with obesity. This combination is extremely common among the obese and makes them vulnerable to diabetes, heart disease, stroke, hormone imbalance, some cancers and a long list of other disorders. Last week's column described how fat can damage your liver.

Research has shown that fat cells are not just harmless globs designed to store fat. They also manufacture a variety of powerful chemicals with a wide array of actions. They can create inflammation and pain in your body, put your sex hormones out of balance or elevate your levels of bad cholesterol and triglycerides.

The takeaway message is that even if your weight is normal, too much hidden body fat compromises your health and puts your life at risk.

HOW FAT ARE YOU?

Check your body weight: This is the easiest test, but as explained above, your body weight measurement does not indicate how much of that weight is fatty tissues. A normal body weight does not mean that you are not obese, but if you are overweight the possibility that you are too fat is much higher.

Use your tape measure

Because you accumulate fat around the waist most easily, your waistline is a good indicator of your level of fatness. A waist measurement of more than 34 inches in a woman or more than 38 inches in a man will increase their risk of diabetes, high blood pressure and stroke by more than 500 per cent.

Calculate your Body Mass Index (BMI): This is what experts in obesity have traditionally used in their research. However, it still does not say how much fat is in your body.

The BMI - the tool normally used to determine obesity - may sometimes fall short as an indicator of good health. BMI is obtained by dividing your weight in kilograms by your height in metres squared.

BMI 18.5 to 24.9 - normal weight.

BMI of 30 or higher - obesity

BMI 25 to 29.9 - overweight.

Measure your percentage body fat:

There are many ways to do this. You can input your age, sex, weight and waist measurement into a programme that will provide you with a fairly accurate estimate of your body fat percentage. More sophisticated machines use bio-impedance technology to send a tiny electrical current through your body and give you a reading of your body fat.

Research facilities use other techniques involving immersion in a tank of water or MRI scanning to most accurately determine body fat percentages. For the average person simply wanting to improve their health status, the simpler methods are quite satisfactory.

Please feel free to contact me for a free body fat analysis.

You may email Dr Tony Vendryes at vendryes@mac.com or listen to 'An Ounce of Prevention' on POWER 106FM on Fridays at 8 p.m.

Age-Adjusted Body Fat Percentage

Women

Age Under-fat Healthy Range Overweight Obese
20-40 yrs Under 21% 21-33% 33-39% Over 39%
41-60 yrs Under 23% 23-35% 35-40% Over 40%
61-79 yrs Under 24% 24-36% 36-42% Over 42%

Men

Age

Under-fat Healthy Range Overweight Obese
20-40 yrs Under 8% 8-19% 19-25% Over 25%
41-60 yrs Under 11% 11-22% 22-27% Over 27%
61-79 yrs Under 13% 13-25% 25-30% Over 30%

Source: Gallagher et al. Am J Clin Nut 2000; 72:694-701