Womens Health

Guidelines for Healthy Weight

Frederick R. Jelovsek MD

What should I weigh? The answer might be based on your age (older women will need to weigh less) , on your desire to be at low risk for death due to obesity-related diseases, or just according to how you wish your body to look.

As far as your health goes, avoiding an excessive amount of body fat is the best way to lower your risk from heart disease, hypertension, diabetes and even from developing gall bladder disease. Sometimes, it is questionable as to what is ideal body weight.

A recent journal supplement, Chez RA (ed.): Weighing the options on managing obesity. Contemporary Ob/Gyn 1999; June supplement:3-30, looks at the issues of weight and health and what is the best way to manage weight problems.

Is the body mass index (BMI) the best measure of how much fat is in my body?

Body mass index, BMI, is only an indirect measurement of body fat. For scientific research purposes there are more accurate methods of measuring what percent of a body's weight is composed of fat such as hydrodensitometry (underwater weighing) and dual-energy x-ray absorptiometry. Physical measurements such as waist and hip circumferences and skin fold thickness in the back of the elbow are also used.

The BMI happens to be the most commonly used measurement in epidemiologic studies and for middle-aged men and women, it correlates over 90% with fat mass densitometry. For older adults who tend to have less muscle mass proportionally, it loses some of its accuracy as an absolute measurement.

The BMI is also called the Quetelet index and is calculated by the weight in kilograms divided by the square of the height in meters. While it does not distinguish fat mass from lean or muscle mass, it is a very useful approximation to what one should weigh depending on height.

What are the health complications of obesity?

In order to determine what people should weigh, researchers have looked at risk of death by different BMI categories in order to determine what would be ideal. Keep in mind that excess weight can have health-associated problems that do not result for quite a while.

It can make arthritis or low back problems worse, cause diabetes and gall bladder disease. Risk of Type II diabetes (usually adult onset) rises in women at a BMI of over 22 even though the normal range for BMI is 19-25. Deaths from cardiovascular disease in non-smoking women rises slightly at a BMI of 22-25 but takes a dramatic jump at a BMI of over 30.

Each kilogram (2.2 lbs) of weight loss will reduce systolic blood pressure (the first number) by .43 mm Hg and diastolic blood pressure (the second or bottom number) by .33 mm HG in women who have hypertension.

Certain cancers have also been associated with excess weight. Cancer of the gall bladder, breast, uterus and ovaries are more common in obese women and weight loss seems to significantly reduce these risks. Obesity is also a risk factor in for osteoarthritis which is the condition responsible for more than 70% of hip and knee replacements. In overweight individuals weight loss of an average of 11 lbs (5 kg) reduced the risk of developing osteoarthritis by more than 50%.

BMIs of 28-30 have a 2.4 times risk of infertility and ovulatory disorders compared to women with a BMI of 20-22. Excess hair growth and acne can also be associated with increased weight and disappear with weight loss.

What is the definition of overweight or obesity?

While BMI is not the perfect measurement for assessing increased body fat, it is the most easily obtained measurement that has a high correlation with percent of body fat so most of the standards are set using BMI.

Even though there can be some increased health risks within the upper limits of the normal range, various groups such as the World Health Organization, the American Institute of Nutrition and the International Obesity task force, among others have given some guidelines.

Weight Category Definitions

Classification BMI Body Mass Index
Underweight less than 18.5
Normal 18.5 - 24.9
Overweight 25.0 - 29.9
Obesity 30.0 - 39.9
Extreme Obesity 40.0 and greater

You may
calculate your body mass index in pounds or kilograms or look up on the table where your current BMI puts you.

I will never get to my ideal weight -- why even try?

It can be extremely difficult for an obese person to lose weight down to an ideal level. Fortunately many studies show a huge reduction in mortality and weight related problems with even a modest reduction of 5-10% weight loss which is maintained for at least a year.

In fact, losing large amounts of weight does not lower the mortality further than just a 10% weight loss does. Nurses who lost 11 kg (24 lbs) had a risk of type 2 diabetes that was 75% lower than nurses with unchanged weight.

Thus the overall goal should be weight loss but not necessarily all the way to ideal body weight. A 10% loss occurring at a rate of 1-2 lbs per week is what most weight management specialists recommend.

When should diet pills be considered in the management of weight problems?

Various prescription medicines that aid in weight loss have come on and off the market over many years. Some have had dangerous side effects only discovered after years of use. Most have only a temporary effect on aiding weight loss.

As each newer medicine comes available promising effortless weight loss, weight management experts still prefer non medication aided dieting and behavioral modification. There are circumstances in which the experts resort to medicines.

  • individuals with a BMI of over 30 and who have serious health complications
  • individuals with appetite problems to the extent that a women reports she is always thinking of food or has constant food cravings
  • more than one or two failures at weight loss or maintenance of weight loss using behavioral therapy

Surgical bypass therapy should be considered for women who have BMIs of 40 or over 35 with obesity health complications.

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