Are You Overweight? Using the New NIH Weight Guidelines

Source: Health Spotlight, Judith M. Ashley, Ph.D., R.D.

Introduction

If you are facing the effects of "creeping" weight gain, how do you know when you should really get serious about losing those extra pounds? After all, based on the growing percentage of Americans who are overweight (see Table 1), it is likely that many of your friends, colleagues, and relatives are experiencing the same weight gain. How do we know if those "love handles" are not just a middle age phenomenon or a problem that you need to deal with?

In 1998, The National Institutes of Health (NIH) issued standards to help you determine if you are overweight or obese. These standards are based on the most extensive review of the scientific literature conducted to date regarding the relationship between weight and health risk by the Obesity Education Initiative Expert Panel. The Panel systematically evaluated published scientific literature from 1980 to 1997. The report established guidelines, or "standards of care," for physicians and health professionals to utilize in managing patients with a broad range of weight problems. The guidelines included what measurements to use to determine if a person is overweight or obese, as well as how to initiate and maintain a weight loss program.

The NIH recommends two measurements that you can determine at home---the body-mass index (BMI) and waist circumference---which will give you an accurate idea of what shape you are really in. These numbers go beyond a simple bathroom scale reading or a number from a weight-for-height table hanging in your physician's office.

Taking the Right Measurements

Body Mass Index

The BMI describes body weight relative to height and is strongly correlated with how much body mass, including fat, a person has. To calculate the BMI, either weight in pounds and height in inches OR weight in kilograms and height in meters, can be used. The BMI is the weight in kilograms divided by the height in meters squared [wt (kg)/ht (m)2] or the weight in pounds divided by the height in inches squared times 703 [wt (lbs.)/ht (in)2] ] x [703] (see Table 2). For example, for someone who is 5'7" tall, their BMI would be 25 at 159 pounds, or their BMI would be 30 at 191 pounds (see Table 3). The range that is considered healthy is between 19 to 25. A person with a BMI of 25 or greater is considered overweight; with a BMI of 30 or greater the person is considered obese; and with a BMI of 40 or greater, the person is considered extremely obese. Solid evidence demonstrates that the risk for various diseases rises significantly when the BMI is over 25 and that risk of death increases as the BMI reaches and surpasses 30. The BMI number applies to both men and women. Some people who are very athletic and have a heavier muscle mass may have a higher BMI without the same health risks. The BMI is also used to determine whether weight loss drug prescriptions or surgery should be considered. FDA approved weight loss drugs are only recommended for those with a BMI > 30, or a BMI > 27 when an obesity-related disease already exists. Surgery for weight loss is an option when conventional methods have failed for those with clinically severe obesity measured by a BMI > 40, or a BMI > 35 with an obesity-related disease.

Waist Circumference

The waistline, or waist circumference, is a familiar body dimension that reflects abdominal obesity. The easiest way to measure yourself at home is by measuring your waistline at the level of the navel or at the narrowest waist midpoint using a tape measure. A health professional may be more specific in this measurement, using the midpoint between the lower border of the rib cage and the crest of the hip. A woman with a waist circumference over 35 inches (88 cm), or a man with a waist circumference over 40 inches (102 cm), is carrying too much fat around the abdominal organs. Fat around the middle changes the way the body uses fat, which can lead to diabetes, heart disease and cancer. Fat in a large abdomen is more likely to break down and enter the blood where it can clog the arteries.

NIH Weight Loss and Maintenance Recommendations

The NIH guidelines also include strategies for weight loss and maintenance. The first recommended strategy is to focus on reducing overall calories. The diet should be individually planned to help cut back between 300 and 1,000 calories a day. It is estimated that 3,500 calories translates into approximately 1 pound of weight loss, so cutting back on 500 calories over 7 days would mean a 1 pound weight loss in a week. As an example, for those with a BMI in the typical range of 27 to 35, a decrease of 300 to 500 calories per day will result in weight losses of about 1/2 to 1 pound a week and a 10 percent loss in 6 months. For more severely obese people with a BMI > 35, cutting back on 500 to 1,000 calories per day will lead to weight losses of about 1 to 2 pounds per week and a 10 percent weight loss in 6 months. If further weight loss is necessary, an evaluation is made at that point, with adjustment of the diet plan, since it is common to see the rate of weight loss decline and plateau after 6 months because of reduced energy expenditure (lower basal metabolic rate) at the lower weight.

The second recommended strategy takes into account the output part of the energy balance equation: physical activity and exercise. Increasing the loss of calories through physical activity not only helps with weight loss, but it also has benefits of its own, including improvement in physical fitness and appearance. Physical activity should be initiated slowly and become part of any weight loss or maintenance plan. The recommendation is to start out with 30 to 45 minutes of activity, three-to-five days a week, including activities such as walking or swimming at an acceptable pace. With this regimen, an additional expenditure of 100 to 200 calories per day is possible. The goal is to reduce sedentary activity (sitting, lying down, etc.). For many people this translates into a simple habit of getting up and walking as often as possible throughout their normal day. (Please see our article, Weight Loss and Physical Activity, for further information on this topic.)

Summary

The NIH guidelines discussed in this article will be influential on many fronts. By classifying certain measurements into categories (overweight, obese, extremely obese), it will help people decide if they should ask their doctors about their weight problems and the risk it may be posing to their overall health. It will also help physicians and other health professionals to determine if a particular patient should start a weight management program, and what type of goals should be set. Furthermore, since these NIH guidelines are considered the "standard of care," they are laying the groundwork for the types of services and medications covered by managed care companies and other insurance plans in the area of weight management.

Table 1
Overweight and Obesity Trends in US Adults (age 20 and older)

Table 2
NIH Guidelines and Calculations

NIH Weight Standards:
BMI > 25 = Overweight
BMI > 30 = Obese
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Waist Circumference > 35 inches (88 cm) for women
Waist Circumference > 40 inches (102 cm) for men
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How BMI is calculated
Metric Conversion Formula
weight (kg)/height (m)2
Example: 78.93 kg/(1.77 m)2 = 25
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Non-metric conversion formula
[weight (pounds)/height (inches)2 ] x [703]
Example:[164 pounds/(68 inches)2] x [703] = 25
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Physical Activity Recommendation
30 to 45 minutes, 3 to 5 days a week
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Weight Loss Recommendations
5% to 10% of body weight or 1 to 2 pounds per week



Table 3
BMI by inches and pounds