BMI levels for overweight and obesity are given by the World Health Organization according to a WHO Consultation on Obesity (Geneva, 3-5 June 1997):
For assessing obesity in adult populations, the BMI categories were given as:
"BMI 25 kg/m2 for overweight
BMI 30 kg/m2 for obesity:
- Class I obese: BMI 30-34.9 kg/m2
- Class II obese: BMI 35-39.9 kg/m2
- Class III obese: BMI 40 kg/m2.
The advent of childhood obesity was of particular concern, the meeting noted, as well as the particular susceptibility of some ethnic groups, particularly in Asia, to weight gain and accumulation of abdominal fat."
An increase in BMI is associated with a rise in sympathetic nervous system activity as demonstrated for skeletal muscle nerve activity.