US researchers have concluded in their study that extra weight is not necessarily linked with a higher risk of death.
When UC Davis researchers compared the data to those with normal weight, people who were overweight or obese had no increased risk of death during a follow-up period of six years.
People who were severely obese did have a higher risk, but only if they also had diabetes or hypertension.
The findings call into question previous studies — using data collected when obesity was less common — linking higher short-term mortality with any amount of extra weight.
“There is currently a widespread belief that any degree of overweight or obesity increases the risk of death, however our findings suggest this may not be the case,” said Anthony Jerant, professor of family and community medicine and lead author of the study.
“In the six-year timeframe of our evaluation, we found that only severe obesity was associated with an increased risk of death, due to co-occurring diabetes and hypertension,” Jerant said.
Based on the study, Jerant recommends that doctors’ conversations with patients who are overweight or obese, but not severely obese, focus on the known negative effects of these conditions on mental and physical functioning, rather than on an increased short-term risk of death.
By contrast, Jerant added that it is important for doctors to talk with severely obese patients who also have diabetes or hypertension about their increased short-term mortality risk and treatment, including weight loss.
“Our results do not mean that being overweight or obese is not a threat to individual or public health,” Jerant said.
“These conditions can have a significant impact on quality of life, and for this reason alone weight loss may be advisable,” he said.
In conducting the study, Jerant used nationwide data from 2000 to 2005 of nearly 51,000 adults aged 18 to 90 years who participated in the Medical Expenditure Panel Surveys on health-care utilization and costs.
The surveys include information on health conditions such as diabetes and hypertension.
Mortality was assessed using the National Death Index. Of the 50,994 people included in the UC Davis analysis, just over 3 percent (1,683) died during the six years of follow-up.
The investigators found that severely obese people were 1.26 times more likely to die during follow-up than people in the normal weight group.
However, if people with diabetes or hypertension were eliminated from the data, those who were overweight, obese or even severely obese had similar or even lower death rates than people of normal weight.
Consistent with a number of prior studies, underweight people were nearly twice as likely to die than people with normal weight, regardless of whether diabetes or hypertension was present.
“Our findings indicate that the risk of having an above-normal BMI may be lower than in the past,” Jerant added.
Jerant said that the six-year period of his investigation limits the ability to make assumptions about the link between unhealthy weight and the risk of death over a longer timeframe.
The findings appear in the July-August issue of The Journal of American Board of Family Medicine.