Friday, January 10, 2014

Can You Be Overweight Yet Totally Healthy?

Are metabolically healthy overweight and obesity benign conditions? Annals of Internal Medicine 2013;159:758-69.

Objective
A recent study suggested that the overweight have a lower risk of mortality than those that are at a normal weight. A minority subgroup of obese individuals on the surface seem to be completely healthy. They have no negative metabolic consequences that are normally associated with weight gain, such as high blood pressure, insulin resistance, high cholesterol, etc. This investigation examines whether there is a class of “benign” obesity that does not increase risk of disease.

Methods
This paper is a meta-analysis of 8 studies that compare risk of all-cause mortality and/or cardiovascular events in 5 categories of individuals:

1) Normal weight and healthy
2) Normal weight and unhealthy
3) Overweight and healthy
4) Overweight and unhealthy
5) Obese and healthy
6) Obese and unhealthy 

Healthy individuals lacked any of the normal risk factors for heart disease such as: high triglycerides, low HDL, high blood pressure, high blood glucose, etc. Normal weight is considered a BMI under 25. Overweight is considered a BMI of 25.1-29.9. Obese is considered a BMI greater than 30.

Results
Those that were of normal weight and healthy were considered the reference group. Compared to these subjects, those that were unhealthy and obese had a 265% increased risk of death or cardiovascular events. Those that were overweight and unhealthy had a 270% increased risk of death or cardiovascular disease. Those that were normal weight and unhealthy had a 314% increased risk of death or cardiovascular events. Those that were overweight and healthy had a non-significant 21% increased risk, while those that were obese and healthy had a 25% increased risk.

Comment
Studying the effects of weight on mortality is really challenging. People who smoke are thinner than average and die younger than nonsmokers. People who are sick often lose weight for years before they die. So, sometimes it looks like thinner people die younger than those who are a bit heavier. However, when these issues are properly controlled for, the research literature shows a strong association between overweight, obesity, and early mortality. This study confirms this idea. Subjects who were obese but otherwise healthy had a significant increase in risk of early death or cardiovascular events. 

Take Home Message
Despite recent headlines to the contrary, being overweight is unhealthy. If your BMI is above 25, work to get it lower. If it is below 25, do your very best to keep it there.

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