The Development of Obesity in Young U.S. Adults, 1981–1998

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The summary below is from the full report titled "The Natural History of the Development of Obesity in a Cohort of Young U.S. Adults between 1981 and 1998." It is in the 18 June 2002 issue of Annals of Internal Medicine (volume 136, pages 857-864). The authors are KM McTigue, JM Garrett, and BM Popkin.

What is the problem and what is known about it so far?

Americans are becoming overweight at an alarming rate. In 1960, about 31% of Americans were overweight and 13% were obese. By 1999, 35% of Americans were overweight and 26% were obese. Body mass index (BMI) is a way to measure whether a person is of appropriate weight. BMI is calculated by dividing a person's weight in kilograms by the square of his or her height in meters (BMI = weight in kilograms/height in meters ²). An appropriate BMI is between 18.5 kg/m² and 25 kg/m². People with BMIs less than 18.5 kg/m² are underweight, people with BMIs between 25 and 30 kg/m² are overweight, and people with BMIs 30 kg/m² or greater are obese. Obesity is a serious public health problem because obese people are more likely than normal-weight people to suffer from chronic health problems, such as high blood pressure or diabetes, and to die at younger ages. Knowing at what age people are likely to become obese and which groups are at high risk for obesity will be helpful in developing ways to prevent this serious health problem.

Why did the researchers do this particular study?

To determine at what age young adults become obese and whether sex, ethnic background, or year of birth is related to the development of obesity.

Who was studied?

9179 people who were born between 1957 and 1964 and who participated in the National Longitudinal Survey of Youth 1979. The purpose of this survey was to gather information on the workforce activities and other life events of young U.S. citizens.

How was the study done?

The survey gathered information on height in 1981 and on weight 12 times between 1981 and 1998. Using this information on height and weight, the researchers determined at what ages people became obese. They then determined whether sex, ethnic background, and year of birth were related to the age at which people became obese.

What did the researchers find?

By age 35 to 37 years, 26% of men and 28% of women were obese. Black women became obese earliest, followed by Hispanic and then white women. Hispanic men became obese earliest among the men. People born more recently tended to become obese at earlier ages than those who were born in less recent years.

What were the limitations of the study?

This study did not examine factors, such as diet and exercise, that might explain the male–female and ethnic differences in the development of obesity. Without knowing why certain groups become heavier sooner, it is difficult to develop specific strategies to prevent weight gain.

What are the implications of the study?

Obesity starts in early adulthood. To prevent obesity, strategies should target young adults. Special prevention strategies might focus on ethnic groups at highest risk for becoming obese by the mid-30s.