Being overweight is a health concern, but Body Mass Index doesn't tell the whole story because it is part of a larger picture, says a new advisory
by the American Heart Association published this month.
Lead author Dr Cora E. Lewis, professor of medicine and public health at the University of Alabama at Birmingham, said that:
"This larger picture includes important relationships between BMI and other health outcomes, such as cardiovascular disease and its risk factors."
"Arguably, the most important relationship among the cardiovascular disease risk factors is diabetes, which is significantly more common in overweight than in normal-weight people," she added.
The advisory is published in the 8 June online issue of Circulation, the Journal of the American Heart Association.
Many studies looking at the relationship between Body Mass Index (BMI, the ratio of a person's weight in kilos to the square of their height in metres) and risk of death from all causes (total mortality) contradict each other. The authors argue that looking only at death from all causes overlooks the important part that being overweight might play in the development of cardiovascular disease risk.
And BMI is not enough to tell the whole story. An assessment of a person's health risk due to being overweight should also take into account the amount of lean mass or muscle, which reduces health risk, and where the fat is distributed on the body, for instance around the waist presents higher risk than around the hips.
Lewis and colleagues concluded that:
- Being overweight increases the risk of cardiovascular disease, type 2 diabetes and other health conditions.
- Being overweight usually precedes being obese, so everyone who is overweight, adults and children alike, should reduce weight by changing to a healthy diet and doing more exercise.
- More research is needed on the links between overweight and health and this should go beyond looking only at BMI and risk of death.
"Meanwhile, we cannot afford to wait for this research to begin addressing the problem of overweight in our patients and in our society."
"Both healthy eating patterns and physical activity have roles in managing weight and CVD risk and should be encouraged in all," they wrote, explaining that gaining weight is progressive while losing weight is very hard to manage.
About one-third of Americans are overweight, which in BMI terms sits between normal and obese, ranging from BMI of 25.0 to 29.9. Also, the number of overweight children is going up, and overweight children usually turn into overweight and obese adults, said the authors.
Even among children, being overweight is linked to higher risk of developing risk factors for cardiovascular disease, such as obesity, high blood pressure, obesity, higher levels of cholesterol and type 2 diabetes, they warned.
Lewis and colleagues also said it was also important that health professionals:
"Consider the overall risk status of patients regardless of BMI, with the realization that those with [cardiovascular disease] risk factors such as type 2 diabetes mellitus and systemic hypertension are at particularly increased risk from excess weight and may well benefit from weight loss intervention as part of their treatment."
"Mortality, Health Outcomes, and Body Mass Index in the Overweight Range. A Science Advisory From the American Heart Association."
Cora E. Lewis, Kathleen M. McTigue, Lora E. Burke, Paul Poirier, Robert H. Eckel, Barbara V. Howard, David B. Allison, Shiriki Kumanyika, and F. Xavier Pi-Sunyer.
Circulation, Published online Jun 8, 2009.
Written by: Catharine Paddock, PhD