Dear Dr. Blonz: My question relates to the recent headline that being overweight (as opposed to obesity) may not be such a serious health problem. How do you see this message? – FS, Atlanta

Dear FS: Statistics can reveal mathematical relationships between different things, and these relationships may or may not explain what is going on. Such research can also reveal strange relationships that may have little to do with reality. I remember finding that doctors who eat more meat and consume more alcohol have a much lower risk of dying in a plane crash. This is more of an amusing statistical quirk, not an indication that doctors need to grab a burger and beer before boarding a flight.

Carrying a little extra weight is not incompatible with good health and long life. Conversely, being at or below a “normal” weight is no guarantee of health or longevity – in fact, being classified as underweight can be negative. Healthy foods and an active lifestyle, including activities that you enjoy and that reduce stress, are the key elements. These critical distinctions can be lost in the type of large-scale population studies that are used to arrive at conclusive conclusions.

A standard measure of body weight is the Body Mass Index (BMI), which is calculated based on height and body weight. A BMI of less than 18.5 is considered underweight; 18.5-25 is the ideal body weight; 25-30 is overweight; more than 30 are obese; and over 40 are considered extreme obesity. (More about BMI at To be classified as overweight means that your own weight is above the ideal, but not obese. Back to that heading, one widespread population study reported a slight benefit from being overweight (though not obese), but later studies tended to question those results. (More on this discussion at