People are often concerned about their weight because fashion trends and celebrities’ physical appearances influence popular body-image ideals—but these ideals do not necessarily represent healthy weight ranges.
Since people usually increase their body fat when they gain weight, overweight often leads to health risks. However, not all weight gain represents excessive fat. Weight gain in bodybuilders, for example, is due to increases in muscle that is part of the body’s lean mass, and there is no evidence that increased lean body mass is unhealthy. Similarly, weight gain during pregnancy is a natural and essential process for supporting foetal growth. Health concerns about overweight are actually concerns about the effects of excess body fat on disease or the risk of disease.
In 1998, a report containing the conclusions of a panel of health experts set guidelines for deciding when excess weight should be considered a health risk. They determined that three pieces of information were needed to decide whether weight loss should be recommended to improve current and future health:
Health professionals currently use the Body Mass Index (BMI) to estimate the health risks associated with being overweight or underweight. BMI is calculated by one of the following methods:
You can also obtain a simple measurement of BMI using following chart. Find your height in the left-hand column, then follow the bottom row to the right until you reach your weight. From left to right, the four chart areas show the ranges of low, normal, high, and very-high BMI.
The Body Mass Index is only one tool for assessing health risks associated with weight. To learn more, read this full article and see a health professional for a more precise assessment.
Note: For a very muscular person, a high BMI does not necessarily indicate overweight, since the extra weight might be muscle, rather than fat.
Abdominal fat has been recognised as the type of fat leading to the highest health risks compared with fat located elsewhere in the body. Waist circumference is considered a good indication of the amount of abdominal fat a person is carrying.
To measure waist circumference, the top of the upper-right hip bone (known as the iliac crest) is marked and a measuring tape is passed around the abdomen at this level. The tape should be snug but should not compress the skin, and the waist circumference measurement should be made at the end of a normal breath following exhalation.
People with weight-related diseases such as cardiovascular disease, and those who have high risk for those diseases, may need to lose weight, even if they are only moderately overweight, in order to promote optimal health.
If you have been told you have coronary heart disease, symptomatic carotid artery disease, peripheral arterial disease, abdominal aortic aneurysm, type 2 diabetes, or sleep apnea, you are in the high-health-risk category for the purpose of determining whether you should lose weight. You are also in this category if you have any two or more of the following heart disease risk factors:
Some less serious diseases are also related to excess weight, and overweight people with these diseases are usually advised to lose weight. These diseases include gallbladder disease, osteoarthritis, stress incontinence, and gynaecological problems such as excessive menstrual bleeding (menorrhagia) and loss of menstrual periods (amenorrhoea). Consult your doctor to find out whether any other health problem you have is related to excess weight.
According to the report of the expert panel in 1998, people should lose weight if they fit any of the following descriptions using the above measures of weight, waist circumference, and health risks:
Height-weight charts such as those published by the Metropolitan Life Insurance Company were once popular for determining appropriate body weight. However, these charts have been criticized because they were based on risk of death rather than disease, and because they were not representative of the entire population of men and women.
Since health concerns about overweight are actually concerns about the effects of excess body fat on disease or the risk of disease, it could be useful to measure body fat directly. A few methods for measuring body fat are available in health clinics, fitness centres, college athletic departments, and other facilities. All of the following can be reliable for estimating body fat if the person performing the measurement is well-trained and if the equipment is of good quality and in optimum working condition:
Although the above methods are considered potentially reliable for estimating body fat, no well-researched guidelines exist for determining what levels of body fat are detrimental to health, and there is no agreement about how to use these measurements to decide when weight loss should be recommended. Excessive percentage body fat has been suggested to begin at 21 to 25% for men and 31 to 32% for women depending on the authority, but more research is needed to confirm this.
Some authorities believe that too much public health emphasis is placed on losing excessive weight instead of focusing on the promotion of a healthy lifestyle, including diet, exercise habits, and other behaviours that reduce the risk of disease. They point out that not all obese people have increased health risks, and that weight-loss programmes frequently fail in the long term, or result in only an insignificant amount of weight loss. At the same time, healthy lifestyle changes often result in a reduction in disease risk and other important health benefits, even if weight change is not impressive.