A "normal" weight - with BMI between 22.5 and 24.9 - was linked to lowest risk
by Hank Dart
It turns out that a healthy weight is a healthy weight. That's the essential conclusion of a large and well-designed new study looking at long term weight and its relation to premature death. What makes this seemingly common sense finding especially newsworthy is that it runs counter to some recent high-profile studies that have concluded that being overweight or slightly obese may actually provide the best protection against premature mortality, even more so than being at what is classified as a "normal" or "healthy" weight. Not surprisingly, these past "obesity paradox" studies made a splash in both the media and scientific circles, grabbing headlines the world over. Yet, many researchers had concerns about the design of these studies, and therefore the
trustworthiness of their findings. The main issue was that the studies did not seem to adequately take into account smoking status and pre-clinical disease, which can have an important impact on both weight and the risk of death. Pre-clinical disease is an illness that has not yet been diagnosed but that can lead to weight loss and increased risk of dying. And weight loss from such illness can happen many years before it is diagnosed. Likewise, smokers also tend to weigh less and have a higher risk of dying. Unless a study is designed correctly, each of these factors can incorrectly sway results to show that being a normal weight increases the risk of death, and being overweight lowers risk. This new study, performed by researchers at the Harvard School of Public Health and Harvard Medical School, was design to address such issues by using participants' maximum weight over a 16-year period. This way, the impact of weight loss due to pre-clinical disease could be limited. A participant with a maximum weight in the "normal" category, for example, would not have gotten there by losing weight -- such as due to an unknown illness.
Following 225,000 middle-aged men and women for another 8 - 20 years, the researchers found a steady increase in risk of premature death with overweight and obesity, compared to normal weight (see figure). Underweight also increased risk in women. The lowest risk of premature death was with a body mass index (BMI) between 22.5 - 24.9, which is a weight of 148 - 164 pounds for someone 5 feet, 8 inches tall.
While these findings are not necessarily surprising - since they fall in line with the guidelines for healthy weight and unhealthy weight - they are quite an important counter to the widespread "obesity paradox" coverage. Next to smoking, weight is the most important health issue in the nation - and increasingly the globe. In addition to lowering quality of life, overweight and obesity increase the risk of heart disease, diabetes, stroke, osteoarthritis, liver disease, and thirteen different cancers.
Working to maintain a healthy weight remains one of the best things people can do for their health and well-being. While it's not easy, it's certainly worth it.