The fashion industry is rarely logical or rational, but they're probably not going to like a growing consensus in the scientific community: Namely, that it's better to be overweight than excessively skinny.
This doesn't mean that you're off the hook on exercise and eating right. Eating crap and sitting on the couch is still going to kill you. But it turns out that starving yourself and running for ten hours can also kill you.
Essentially, study after study indicates that if you've got a chronic disease, such as diabetes, being skinny is more likely to kill you than being overweight. But why?
First of all, the word "obese" is tricky to define. Many studies use the Body Mass Index, or BMI, which was developed by a Belgian social scientists in the 1800s with no medical training, to define it. The problem is that a bodybuilder is technically "obese" under the BMI because he's heavy. He may have health problems: Obesity, however, is almost certainly not one of them.
In other words, the obese person may actually be at a reasonable weight by other scientific measures. But we don't know, because there's no widely accepted method of measuring obesity other than... the BMI.
Secondly, it's not really clear how fat is too fat. I know people that could run me into the ground with little trouble, and they're not what you call rails. Plenty of people are overweight or obese and in good health. It's a riddle.
The problem is that people define healthy as a "look" when it's a set of habits. If you eat a healthy diet, get an hour of exercise a day, and avoid stress, you're doing a lot for your health. But science has also found that the body tends to cling to weight. On some level, we're still a species convinced a starvation period is right around the corner.
So what to do with this paradox? Simple: Eat a healthy diet, get exercise daily, and work on reducing your stress. Health isn't about looking good. Health is about feeling good, about being there for the people who love you, about having the energy to spare to hang out with friends. Develop good habits, and there are rewards waiting... even if they're nothing to do with looks.