By Dr. Brian McDonough, Medical Editor

PHILADELPHIA (CBS) – It is well known that obesity is linked to heart disease but what about being too thin?

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You might be surprised that research has found that being underweight puts people at even higher risk of dying early than obesity. Underweight adults with a body mass index, or bmi, less than 18.5 were about 70% more likely to die during the study period than those with a normal body weight.

The information was based on a review of over 50 studies.

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In case you are wondering whether some of the thin people were very sick, this was accounted for. Those with chronic or terminal illness were taken out of the final report.

The researchers said that someone can be underweight but still have a high body fat percentage. This could increase their risk for problems.

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The report is from The Journal of Epidemiology.