|
Friday, 19 May 2006 |
|
By Elena Voropay Since the mid-seventies, the prevalence of overweight and obesity has increased sharply for both adults and children. The rates are underestimated because overweight people tend to underestimate their weight and overestimate their height. It is different from being overweight, which means simply weighing too much. While general body weight may come from muscle, bone, fat and/or body water, obesity means having too much body fat. This is what cracks the puzzle of lean bodybuilders who weigh more than they 'should' for their hight, but have minimal body fat covering their developed muscles.
Obesity occurs over time when you eat more calories than you use. The balance between calories-in and calories-out differs for each person. Factors that might tip the balance include your genetic makeup, overeating, eating high-fat foods and not being physically active. Measuring the exact amount of a person's body fat is not easy. The most accurate measures are to weigh a person underwater or in a chamber that uses air displacement to measure body volume, or to use an X-ray test called Dual Energy X-ray Absorptiometry, also known as DEXA. These methods are not practical for the average person, and are done only in research centers with special equipment.
There are simpler methods to estimate body fat. One is to measure the thickness of the layer of fat just under the skin in several parts of the body. Another involves sending a harmless amount of electricity through a person's body. Results from these methods, however, can be inaccurate if done by an inexperienced person or on someone with extreme obesity. Because measuring a person's body fat is difficult, health care professionals often rely on other means to diagnose obesity. Weight-for-height tables, used for decades, have a range of acceptable weights for a person of a given height. One problem with these tables is that there are many versions, all with different weight ranges. Another problem is that they do not distinguish between excess fat and muscle. According to the tables, a very muscular person may be classified obese when he or she is not. The BMI is less likely to misidentify a person's appropriate weight-for-height range. |
|
Get Active 
.png)
