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The Relationship between Intentional Weight Loss and Mortality
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What is the problem and what is known about it so far?
Being overweight is bad for health, leading to problems such as high blood pressure, heart disease, and diabetes. Overweight people also die at younger ages than people who are of normal weight. When overweight people lose weight, they often improve their blood pressure and cholesterol levels. However, it remains uncertain whether overweight people who lose weight will live longer than they would have if they had not lost weight. In fact, studies have suggested that losing weight increases a person's risk for death. This surprising result may be because these studies have been unable to differentiate between people who lost weight because they tried to by changing their diet and exercise habits (intentional weight loss) and people who lost weight because they were sick with conditions such as cancer (unintentional weight loss).
Why did the researchers do this particular study?
To look at the relationships between intentional and unintentional weight loss and the risk for death.
Who was studied?
6391 overweight and obese American adults (35 years and older) who completed a 1989 national health survey. The researchers used a measure called body mass index (BMI) to define overweight and obese. Body mass index 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). A normal BMI is between 18.5 kg/m2 and 25 kg/m2. People with BMIs between 25 kg/m2 and 30 kg/m2 are overweight, and people with BMIs of 30 kg/m2 or greater are obese.
How was the study done?
In addition to asking people about their weight, height, and health, researchers asked them: 1) “Have you tried to lose weight in the past year?” 2) “Is your weight now more, less, or about the same as a year ago?” and 3) “In the last year, about how much have you gained or lost?” The researchers used the National Death Index, a national database of deaths in the United States, to see whether the study participants were alive over the next 9 years. They compared the mortality rates (death rates) of groups of people based on intentional and unintentional changes in weight.
What did the researchers find?
Compared with people who reported no change in weight and who were not trying to lose weight, people who tried to lose weight had a lower mortality rate. People who lost weight without trying to had a higher death rate. People trying to lose weight had a lower death rate regardless of whether they lost weight. The lowest death rate was associated with modest intentional weight loss.
What were the limitations of the study?
The study used self-reported weights and weight changes, which may not be reliable.
What are the implications of the study?
Trying to lose weight decreases an overweight or obese person's risk for death, regardless of whether he or she loses weight. Losing weight is associated with dying only if the weight loss is unintentional.
Article and Author Information
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The summary below is from the full report titled “Intentional Weight Loss and Death in Overweight and Obese U.S. Adults 35 Years of Age and Older.” It is in the 4 March 2003 issue of Annals of Internal Medicine (volume 138, pages 383-389). The authors are EW Gregg, RB Gerzoff, TJ Thompson, and DF Williamson.
- Copyright ©2004 by the American College of Physicians
