A recent study showed that there are very few differences in eating habits between people with "normal" BMI and those who are "overweight" and "obese". 75% of the obese say that they eat healthy. Comparable percentages work out, snack between meals, and eat out. Even the numbers who eat everything served are not great enough to explain the difference in body weight. The people conducting the survey did admit that they didn't include the quantity of food eaten. Still, this shows that there may be no simple difference. At the least, the obese are not living unhealthy lifestyles. Consider that other studies that show obesity (but not morbid obesity) has little harmful effect on health. Now combine that with the study I wrote about a couple of days ago showing that people in the 19th century tended to have a "normal" BMI but were subject to chronic health problems and you start to wonder about the "obesity epidemic".
Is it possible that our standards of what is "normal" were set at a time when people were undernourished and unhealthy and that the current "epidemic" is actually what healthy people really weigh?
A few other factors - when doing a story on obesity, TV always shows people who are 50+ pounds overweight but you can be just 10-20 pounds overweight and still be considered obese. The BMI figures were adjusted down in the mid-1990s so that many people who were normal according to the old measure are now overweight or obese.