An article in USA Weekend for November 26-28 starts with "Almost 70% of adults in the USA are overweight or obese " and many will try anything to shed pounds, from crazy fad diets to prescription meds." I hope that only the obese are trying to shed pounds, because those considered overweight, according to the generally accepted definition of overweight, are in a group with a lower mortality rate than those considered normal or obese.
In order to compare desirable weight for people of different heights, it is customary to use the body-mass index (BMI), which corrects fairly well for differences in height and a number of studies have shown that mortality is at a minimum at a body-mass index of 25, which is in the overweight range (actually it is the lower end of the overweight range). I will cite only one of these studies here, but you can find other references and a more complete discussion of desirable body weight in my essay at http://www.lewrockwell.com/orig7/deutsch1.html.
In 1905, K. M. Flegal and her associates published a paper entitled . "Excess Deaths Associated With Underweight, Overweight, and Obesity." JAMA 293: 1861-7 (2005) in the Journal of the American Medical Association and it described studies of the relative death rates of subjects who were underweight, so-called "normal" (BMI from 18.5 to 24.9), overweight (BMI from 25 to 29.9) and obese (BMI of 30 or more). As promised by the title, the authors provided estimates of the excess deaths associated with having a body-mass index not in the "normal" range, but the title (and the conclusions) are a bit misleading, since the excess deaths associated with being in the overweight group are a negative number. That's right, they found that there were 86,094 fewer deaths in the overweight group than in the same number of subjects in the "normal" group. If you define normal as the group with the lowest mortality, then you should award this title to the group they call overweight. You would not be able to come to this conclusion reading the title and conclusions of this paper, and it is only grudgingly and indirectly admitted in the results paragraph by the statement "Overweight was not associated with excess mortality." That's correct, of course. It's associated with lower mortality.
I find it particularly convincing to come to this conclusion on the basis of this paper, because the reluctance of the authors to flag it indicates that it is extremely unlikely that their data collection was marred by attempts to obtain this conclusion. If you check out my on-line essay, you will find a further discussion of this line of thinking.
The impulse to write this was supplied by a recent Op-Ed piece bewailing the increase in "overweight and obesity." As you can see, they are not synonymous.