Feast and Famine
The special issue on obesity [“Feast and Famine”] did not adequately address the skepticism that has developed concerning health research. Too often we have been encouraged to, say, increase our consumption of broccoli or oatmeal, only to then be told that the initial claims were faulty or exaggerated. These inconsistencies often arise from the misapplication of the basic principles of scientific methodology. There is a chronic failure to select unbiased samples, to identify appropriate control groups, to employ reliable statistical techniques and to recognize that correlation does not necessarily imply cause.
Christopher Bruce
Calgary, Alberta

I am a little surprised that you permitted the use of such a fuzzy measurement as body mass index (BMI). Like a number of other people at my gym, I am well into the  “overweight” zone, not because of fat but because once a person carries a substantial amount of muscle, that person rates as overweight on a BMI scale. BMI is not only widely used in both popular works and professional analyses but is cited in public policy making, which makes the notion that it applies to only some part of the population a bit dreadful.
David Seaver
via e-mail

I was disappointed that your solutions for obesity and overeating explored pharmacological interventions and food choices and ignored the interrelation between emotions and food. All addictions, including food obsessions, have the same roots: low self-esteem, a feeling of an inexplicable void, the inability to process emotions or responses to stress, and a sense of being out of control, which manifests as a variety of self-destructive and compulsive tendencies.
Jennifer Delaney
via e-mail

The Consequences of Corpulence
Paul Raeburn should have consulted us before addressing our 2005 paper on the excess mortality associated with levels of BMI in the U.S. in “Can Fat Be Fit?” We did not state or imply that excess fat carries no health risks. On the contrary, we found that death from all causes was more likely among the obese (BMI 30 and over) than among those of normal weight.

We found no excess mortality among the overweight (BMI between 25 and 30)—a finding that has been reported by other large prospective studies such as the Seven Countries Study and the Cardiovascular Health Study. Our study carefully controlled for smoking and other possible confounding factors. Nevertheless, we checked whether the results could have been affected by smoking or preexisting illnesses by running numerous additional analyses. These analyses, published online by the American Journal of Epidemiology in August 2007 and on the Centers for Disease Control and Prevention Web site, found no confounding in our results.

It is important to remember that nutritional reserves may offer a survival advantage in some illnesses. That may be particularly true for the elderly, among whom most deaths occur. [more]

Katherine M. Flegal, Ph.D.
Centers for Disease Control and Prevention

Barry I. Graubard, Ph.D.
National Cancer Institute

Soup Is Good Filling?
In “The World Is Fat,” Barry M. Popkin states that humans did not evolve to become satiated by beverages because water lacks calories. Calories in drinks such as soda contribute to obesity, he explains, because people tend to consume them in conjunction with more calories from food. But many people lose weight by going on soup diets, and he notes that we did evolve to consume breast milk (a breast-feeding baby will get full). Why is it that soup and breast milk can satiate humans if beverages cannot?
Forest Ray
New York City

POPKIN REPLIES: Many studies have shown that soup does make us feel full, whereas caloric and noncaloric beverages do not. We are unsure if this appetite satisfaction is because of the salt or fat in soup, the way it is consumed, our perception of it as a filling food, or other reasons. Similarly, many studies have demonstrated that beverages containing sugar, high-fructose corn syrup or alcohol are handled differently by the body than when sugar or high-fructose corn syrup is incorporated in solid foods; as a result, the overall caloric intake from solid food does not adjust to account for the calories in these beverages. The mechanism responsible for that weaker compensatory response to fluids is unknown. I posited the hypothesis that humans may lack a physiological basis for processing carbohydrate or alcoholic calories in beverages because only breast milk and water were available for the majority of our evolutionary history. Another possibility is that carbohydrate- and alcohol-containing beverages may produce an incomplete satiation sequence that prevents us from becoming satiated on them. George Bray of Louisiana State University, my co-author for a study that will amplify these theories, suggests that one possible mechanism is the way the gastrointestinal tract responds to the form in which it is exposed to nutrients.