Americans born during the early 1960s are likely to become obese earlier in life than those born in the late 1950s, while black women and Hispanic men face the greatest overall risks for obesity, a health study released Monday said.
In findings that could yield important clues to an unhealthy shift in U.S. dietary and exercise habits, the study of 9,179 people now in their late 30s and early 40s found subjects born in 1964 were consistently heavier at specific ages than those born eight years earlier in 1957.
Researchers at the University of North Carolina at Chapel Hill also found the younger group became obese while in their late 20s -- 26 percent to 28 percent sooner than the older group, which staved off obesity until their early to mid-30s.
Overall more than one-quarter of the subjects, all enrolled in the U.S. Bureau of Labor Statistics' National Longitudinal Survey of Youth in 1979, were obese by 37.
The results present a disturbing picture of an obesity epidemic in the United States that has stirred concern about the prospects for weight-related problems such as hypertension, heart disease, diabetes, cancer and depression.
"The most significant finding is this fairly dramatic shift in how quickly obesity developed in the younger group. It's over eight years, but if this trend is continuing, it could have really important implications for the health of the country," said Dr. Kathleen McTigue, co-author of the study.
"By becoming obese at a younger age, you may be developing these other problems at a younger age as well," she added.
The study, published in the Annals of Internal Medicine, suggested younger age groups may be more vulnerable to obesity because of changes in diet and exercise habits.
Meanwhile, the researchers also found people who were overweight by the time they reached the age of 21 were far more likely to be obese by age 37. Women needed to be only mildly overweight to be at risk.
But McTigue, a clinical scholar at the University of North Carolina School of Medicine, said that finding could prove to be a benefit if physicians began aiming intervention programs at overweight children and young adults. "You might be able to prevent the obesity entirely," she said.
Obesity has been increasing at an alarming rate in the United States since 1960. By 1999, the number of overweight people had risen from 44 percent to 61 percent of the national population, while the number of obese people doubled from 13 percent to 27 percent.
Because obesity is difficult and costly to treat, the problem poses a dangerously unhealthy pattern. "Overweight children are at increased risk for becoming obese adults, and obese adults are, in turn, at risk for raising obese children," the study warned.
Research data also showed black women becoming obese more than twice as fast as white women, and Hispanic men reaching obesity 2.5 times as fast as non-Hispanic white men.
Black men and white men tended to gain weight at about the same rate until the age of 28, after which blacks became obese 2.2 times as rapidly as whites.
"It is disquieting to note that obesity is a risk factor for four of the six most frequent causes of death," the authors concluded.