THE ENEMY WITHIN. THE GLOBAL
OBESITY EPIDEMIC .
Dr. René Menguy
PART 7: HOW IS OBESITY MEASURED?
A common scientific axiom is that one cannot understand something without first learning to measure it. So is it for that disease called OBESITY. Years ago, when I went to Medical School, obesity was not considered a disease and, in the general curriculum, was only mentioned in passing as a complicating factor such as making a surgical procedure more difficult.
Things have changed. Today, obesity has global implications, is the target of medical and surgical treatments, and of research aimed at understanding its causes. Before all that, Medicine had to find out how to quantify it, just like methods of measuring blood pressure had to be devised before trying to treat it.
Beginning in the nineteen forties, Insurance companies, aware of the impact of overweight on life expectancy, issued tables of desirable weights according to height and sex. For years, these tables have provided physicians with an actuarially weight-based estimate of a patient’s healthiness. However, these tables do not actually measure one’s “fatness” or “thinness”. That kind of quantifier came with the introduction of the Body Mass Index or BMI around 1980.
There are several formulas for computing one’s BMI . Most readers will prefer the English Formula.
BMI= (Weight in pounds) divided by (Height in inches)2 multiplied by 703
For example a 6’ individual weighing 184 lbs would have a BMI of 24.9.
BMI below 18.5= underweight
BMI 18.5-24.9= normal weight
BMI 25.0 and above= overweight
An approximation of one’s ideal weight can be estimated as follows: assume a 110 pound base for a 5 ft height and add 5 pounds per inch over 5 ft plus 5 pounds (medium frame) or 10 pounds (heavy frame).
When evaluating a patient’s weight, physicians want to know the total body fat because fat’s the tissue adversely impacting health, not the bone or muscle mass. The BMI can be used to determine that.
Knowing someone’s excess weight, one may assume that 70% of it is fat. The remainder consists of lean tissue and muscle. In the obese, muscle takes up a greater fraction of total body weight than normal, because the body has to work harder to support the greater fat mass. Example: the Sumo wrestler.
A weight significantly above ideal is unhealthy. A US Veterans Administration study showed that the mortality rate of obese men aged 25-34 was 12 times greater than that of lean men.
Men and women who are 30% to 40% overweight have a 50% higher mortality rate than lean people, usually from coronary disease connected to obesity by hypertension and atherosclerosis. However, a weight significantly below ideal is even unhealthier.
Normally, the contribution of adipose tissue (fat) and other tissues to body weight is as follows:
BONE, 45% in men and 36% in women
MUSCLE, 15% in men and 12% in women
FAT, 15% in men and 27% in women
ESSENTIAL FAT, 3% in men and 12% in women
STORAGE FAT, 12% in men and 15% in women
OTHER TISSUES, 25% in men and 25% in women
The location of excess fat is even more important to health than the excess weight. Today, it is generally recognized that there are two types fat distribution in overweight individuals.
UPPER BODY OBESITY. Obesity researchers refer to these people, whose excess fat is located around the chest, and especially in and around the abdomen, as having central or visceral obesity. Their risk of developing obesity related complications such as heart disease, diabetes and cancer is very high.
LOWER BODY OBESITY. More common in women, is characterized by the accumulation of fat around the buttocks and upper thighs, sometimes to the excessive proportions reminiscent of the Hottentots indigenous to Africa. They are said to have a pear shape. Although far less prone to the obesity related complications of those with upper body obesity, they often suffer from osteoarthritis in their weight bearing joints and varicose veins.
To determine which type of obesity a patient has, clinicians use the waist to hip ratio.
i)The waist circumference is measured with a tape placed snugly around the waist. It should be 40 inches or less in men and 35 inches or less in women.
i) The hip measurement is obtained by placing the tape around the widest part of the buttocks. Normally, the waist circumference divided by the hip circumference should be: 0.8 or less for women and 0.95 or less for men.
To be continued