Body mass index measures weight relative to height and is often used to evaluate obesity.
Zheng and his colleagues classified respondents into six groups, depending on their BMI at the beginning of the study and how it changed over the 16-year period they were surveyed.
While slightly overweight people (BMI of 25 to 29.9) whose weight was steady had the highest survival rate, those who moved from overweight to obese (BMI 30 to 34.9) were close behind.
"This suggests that among overweight people at age 51, small weight gains do not significantly lower the probability of survival," Zheng said.
The third highest survival rate among the six groups was normal weight individuals (BMI of 18.5 to 24.9) whose weight increased slightly, but stayed within normal range.
Next came the Class I obese (BMI of 30 to 34.9) whose weight was moving upward.
Next to last were normal weight individuals who lost weight. Although the study attempted to control for illnesses among those studied, it may be that many of these individuals dropped weight because of illness.
The most obese individuals (BMI of 35 and over) who continued to add weight had the lowest survival rate of the six groups.
There weren't enough people who started out as overweight and obese and lost weight to include in this analysis, Zheng said.
"We can't really evaluate the effectiveness of planned weight loss on mortality. Even in the normal-weight people in this study, there was no way to tell whether weight loss was planned," he said.
Zheng noted that the study took into account a wide variety of demographic and socio
|Contact: Hui Zheng|
Ohio State University