Short- and Long-Term Risks for Middle-Aged Adults Becoming Overweight or Obese

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The summary below is from the full report titled "Estimated Risks for Developing Obesity in the Framingham Heart Study." It is in the 4 October 2005 issue of Annals of Internal Medicine (volume 143, pages 473-480). The authors are R.S. Vasan, M.J. Pencina, M. Cobain, M.S. Freiberg, and R.B. D'Agostino.

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

Excess weight is a major public health problem in the United States. Overweight and obese people are more likely than normal-weight people to have health problems, such as some forms of cancer, diabetes, high blood pressure, and knee arthritis. They also die at younger ages. Although Americans of all ages are increasingly overweight, many find that middle age is a particularly high-risk period for gaining weight.

Why did the researchers do this particular study?

To learn the short- and long-term risks for normal-weight, middle-aged adults becoming overweight or obese.

Who was studied?

4117 white men and women 30 to 59 years of age.

How was the study done?

Starting in 1971, the researchers regularly measured weights of adults living in Framingham, Massachusetts. They calculated each person's body mass index (BMI) as his or her weight in kilograms divided by the square of his or her height in meters. They classified weight as normal (BMI between 18.5 and 24.9 kg/m²), overweight (BMI between 25 and 29.9 kg/m²), or obese (BMI of 30 kg/m² or greater). They then described how often the adults with normal weights at baseline eventually became overweight or obese within short (4 years) and long (10 to 30 years) time periods.

What did the researchers find?

Within 4 years, 14% to 19% of the women and 26% to 30% of the men became overweight, while 5% to 7% of the women and 7% to 9% of the men became obese. Within 30 years, more than half of the women and men became overweight, while about one third of the women and one quarter of the men became obese. Adults older than 50 years of age became overweight or obese less often than the younger adults.

What were the limitations of the study?

Only white men and women were studied. Black and Hispanic people may gain excess weight earlier and more often than white people. People born more recently tend to become overweight or obese at earlier ages than those who were born in less recent years. Whether the rates of becoming overweight or obese that were observed in this study will apply to people who are middle-aged in 2005 is difficult to determine.

What are the implications of the study?

For middle-aged white Americans, the long-term risks for becoming overweight or obese seem very high.