Obesity generally has been defined as an accumulation of fat (adipose tissue) beyond what is considered normal for a person’s age, sex, and body type. Historically, nutritionists have defined overweight as being between 1 and 19 percent above one’s ideal weight, based on the height-weight tables. A person who slipped over 19 was labeled obese. In an attempt to clarify the concept of obesity even further, experts labeled people who were 20 to 40 percent above their ideal weight as mildly obese (90 percent of the obese fit into this category). Those 41 to 99 percent above their ideal weight have been described as moderately obese (about 9 percent-10 percent of the obese), and those who are 100 percent or more above their ideal weight are identified as severely, morbidly, or grossly overweight (about 1 percent of the obese). Even the terminology (e.g., gross obesity) speaks volumes about the way society views this group of individuals.
The difficulty with defining obesity lies in determining what is normal. To date, there are no universally accepted standards for the most “desirable” or “ideal” body weight or body composition (the ratio of lean body mass to fat body mass). While sources vary slightly, men’s bodies should contain between 11 and 15 percent total body fat and women should be within the range of 18 to 22 percent body fat. At various ages and stages of life, these ranges also vary, but generally, when men exceed 20 percent body fat and women exceed 30 percent body fat, they have slipped into obesity.
Why the difference between men and women? Much of may be attributed to the normal structure of the female body and to sex hormones. As mentioned earlier, when considering how much or how little fat a person should have, it is important to think of body composition in terms of lean body mass and body fat. Lean body mass is made up of the structural and functional elements in cells, body water, muscle, bones, and other body organs such as the heart, liver, and kidneys. Body fat is composed of two types: essential fat and storage fat. Essential fat is necessary for normal physiological functioning, such as nerve conduction. Essential fat makes up approximately 3 to 7 percent of total body weight in men and approximately 15 percent of total body weight in women. Storage fat, the part that many of us are always trying to shed, makes up the remainder of our fat reserves. It accounts for only a small percentage of total body weight for very lean people and between 5 and 25 percent of body weight of most American adults. Female bodybuilders, who are among the leanest of female athletes, may have body fat percentages ranging from 8 to 13 percent, nearly all of which is essential fat.