Navigating the necessity of losing weight, according to BMI
DEAR DR. ROACH: I was confused by your column the other day, as well as the response regarding weight loss to a writer who is losing height due to aging and/or osteoporosis.
Would it be possible to please obtain more information about why it's not necessary to lose weight unless someone is in the morbidly obese range? I am confused. You also said that it's okay to be in the overweight range (of the BMI) and remain healthy. What about the obese range of the BMI?
Many people, including myself, have vacillated between the overweight and obese range for quite a few years, and don't feel healthy and would like to lose weight. I try to eat well, and I exercise regularly. So, I am unclear on why this is considered sustainable unless I reach the morbidly obese range.
I am tired of people's fat phobia; perhaps your column was an attempt to normalize being overweight and obese in order to avoid fat phobia, which is rampant in society. I could understand that perspective. But, I am still curious about the actual health effects of not losing weight or why you said it wasn't necessary. -- K.E.
ANSWER: I try to base my recommendations on evidence when possible, and the evidence is pretty strong that being overweight does not increase a person's overall risk of death. While this area remains controversial, the most recent data suggest that a BMI (the body mass index is a flawed but widely used way of adjusting weight for a person's height) in the overweight range is not a significant harm and, in some studies, may have an improved mortality rate compared with people who are in the "normal" range.
However, people who are obese do have a clear worsening in mortality risk, and the risk depends strongly on a person's waist size. A smaller waist size for both men and women is associated with improved mortality rates at every level of BMI, reflecting the fact that abdominal obesity (a body shape sometimes called "apples") is much different and much worse than obesity around the hips and thighs ("pears"). At very high levels of obesity, called morbid obesity, there is an increase in mortality that gets worse and worse as the BMI goes up.
The reason I do not emphasize weight reduction for patients who are overweight, and for those people who are in the obese but not morbidly obese range, is because the evidence that weight loss improves outcomes is scanty. Further, nearly every obese patient I have had has heard many times that they need to lose weight, and I feel that emphasizing specific behavioral changes, such as modest increases in exercise and specific dietary changes after a careful review of their eating habits, is more likely to improve that person's health than the advice to just "lose weight."
People who are obese and morbidly obese who have diseases related to their weight, such as diabetes, do benefit from weight loss. However, the best evidence from this comes from trials on weight loss surgery, which is not appropriate for many. The newer diabetes drugs that have become available may dramatically change our understanding of the potential health benefits of weight loss, but having witnessed several spectacular disasters from weight loss drugs, I am awaiting more long-term data before making a stronger recommendation on these new classes of drugs when used specifically for weight loss (as opposed to using them for diabetes).
Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.
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