According to the World Health Order (WHO), more than one billion adults are overweight and at least 300 million of them are obese. Since overweight and obesity contribute to multiple potentially fatal diseases, it's important to understand what leads to weight gain and to know what methods are used to determine whether people are overweight or obese.
Causes
An energy imbalance in a person's body causes him to become overweight or obese. If he consumes more calories than he burns, his body stores excess fat. According to the 2001 U.S. Surgeon General's Call to Action to Prevent and Decrease Overweight and Obesity, a person's body weight is determined by his genes, behavior, environment, metabolism, culture and socioeconomic status. However, behavior and environment are large areas that can be adapted to prevent and treat overweight and obesity.
Body Mass Index (BMI)
Physicians often use the body mass index (BMI) formula to assess a person's body weight relative to height. In this way, BMI can be used as a screening tool to determine overweight and obesity. The formula multiplies a person's weight in pounds by 703, divides by inches of height, and then divides again by inches of height. Although the formula may accurately assess body fatness in most people, those who are particularly thin or muscular may receive inaccurate scores.
Assessing Weight
Weight is assessed differently in children than it is in adults because children and teens are in a constant state of physical development. Instead of simply receiving BMI numbers, they are plotted on a chart that indicates their relative positions among all children of the same age and gender. A teen in the 95th percentile or higher for people his age and sex, for example, may be considered obese.
Alternately, adults are simply given a BMI number that corresponds to a range chart. An adult with a BMI score between 25 and 29.9 is considered overweight and an adult with a BMI of 30 or above is considered obese. Other methods of assessing body fat distribution include calculating waist-to-hip ratios, measuring skin fold thickness and waist circumference, and using imaging techniques such as the MRI.
Associated Risks
Weight is more than a superficial issue. Overweight and obese people are at a greater risk for numerous health conditions and diseases, including high blood pressure, coronary heart disease, stroke, type 2 diabetes, cancer, metabolic syndrome, osteoarthritis, sleep apnea, gallstones and reproductive problems.
Gauging Individual Risks
Although BMI may indicate that a person is at risk for certain health conditions related to overweight and obesity, the National Heart, Lung and blood Institute reports that individual risk level can be assessed by looking at two other predictors: waist-to-hip ratio and other risk factors for disease.
Waist-to-hip ratio can be assessed by measuring the smaller circumference of the waist and dividing by the hip circumference at the widest part of the buttocks or hip; a healthy waist-to-hip ratio in women should be no more than 0.8 and in men it should be no higher than 0.95. Other risk factors for disease may include a sedentary lifestyle and pre-existing high blood pressure.
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