送交者: xj 于 2005-4-20, 13:26:25:
In the current issue of JAMA, researchers at CDC examined three NHANES followup data to determine the puzzling effects of obesity on death. The U shaped relationship between body weight (here denoted as body mass index BMI = kg/height^2, height in cm) and mortality has been well-known. Those who are extremely thin (such as BMI less than 18) and those who are obese (such as BMI greater than 30) are prone to die younger than those whose BMI is around 25.
The important and unexpected finding is that the lowest risk point is BMI at the range of 25-30 instead of 20-25. It is a surprise because our common sense is that the thinner, the better if not extremely thin.
The overweight (BMI: 25-30) people account for more than 30% of US adults (total overweight and obese people accounts for 65% of US adults). The finding from this report is certainly a good news for them. The societal and economical benefits are enormous if considering the impact on the weight losing programs, in addition to the psychological effects.
However, obesity is only one of the risk factors of total mortality. It is also known that overweight or obese people who are free of other diseases such as hypertension and diabetes don't have higher risk of death than others. In fact, in many studies, BMI along doesn't have a significant effect on mortality after adjusted for other risk factors.
Furthermore, the BMI is only one dimension of measuring obesity. Central obesity, assessed by waist circumference, is etiologically more important than BMI. In particular, visceral fat and deep subcutaneous fat, fat accumulated within your abdomen, is highly active in energy, lipid, and glucose/insulin metabolisms. Those who have waist circumference greater than 88cm (in women), and 102 cm (in men) are at higher risk of dying than those with don't.
Will discuss more in my blog if I have time and anybody is interest.