How do we Define Obesity and Overweight?

How do we define obesity and overweight?

The prevalence of overweight and obesity is commonly assessed by using body mass index (BMI), defined as the weight in kilograms divided by the square of the height in metres (kg/m2 ). A BMI over 25 kg/m2 is defined as overweight, and a BMI of over 30 kg/m2 as obese. These markers provide common benchmarks for assessment, but the risks of disease in all populations can increase progressively from lower BMI levels.

Adult mean BMI levels of 22-23 kg/m2 are found in Africa and Asia, while levels of 25-27 kg/m2 are prevalent across North America, Europe, and in some Latin American, North African and Pacific Island countries. BMI increases amongst middle-aged elderly people, who are at the greatest risk of health complications. In countries undergoing nutrition transition, overnutrition often co-exists with undernutrition. People with a BMI below 18.5 kg/m2 tend to be underweight.

The distribution of BMI is shifting upwards in many populations. And recent studies have shown that people who were undernourished in early life and then become obese in adulthood, tend to develop conditions such as high blood pressure, heart disease and diabetes at an earlier age and in more severe form than those who were never undernourished.