New genetic research has discovered that people missing a small portion of their DNA, about 30 genes, will become morbidly obese. The missing DNA was not found in any people of normal weight.

The affected people tended to be normal weight as toddlers, became overweight during their childhood, and then became severely obese as adults.

If you're overweight, it's unlikely that this research applies to you directly, as the deletions have been found in only 7 out of every 1000 people.

What the research does suggest for most of us is that genes do matter and can give us a strong likelihood of becoming overweight or a strong likelihood of being skinny.

Most of us know this intuitively. We know that obesity runs in families. Some families tend to be skinny and other families tend to be fat, even if they're eating just about the same things. But skinny people don't believe it. They think they're skinny because they're virtuous and fat people are fat because they're lazy and gluttonous.

Obviously, there are some overweight people who are overweight because they do eat too much. In some cases, they have a genetic defect in their appetite control, so they're hungry all the time, and it's difficult not to overeat when you're very hungry. In other cases, they may be overeating for emotional reasons. Or they may be overeating because they were raised by parents who told them it was sinful to waste food, so they always clean their plates even when they're served too much food.

I see severe weight problems as analgous to a person who is born with some other genetic defect. Imagine a man born with genes that produce too little growth hormone, so the man is only 5 feet tall when he is fully grown. Imagine that he wants to make the college basketball team. Highly unlikely, but perhaps possible. By investing a huge amount of effort, the man might be able to overcome his handicap. Most people wouldn't be willing to invest that much effort.

The same is true of people with genes that predispose them to severe obesity. With a huge amount of effort, they may be able to avoid gaining weight. But the effort is huge, and again, most people wouldn't be willing to invest that much effort.

I don't think the kind of overweight that is most common -- putting on 10 or 15 pounds in middle age --  is likely to be caused by a genetic defect. It's the severe obesity that I would expect to be genetic.

And if a single deletion can cause morbid obesity, it's likely that other genetic differences can do the same. The researchers are continuing to look for other gene defects associated with morbid obesity.

Clearly, even if you have a genetic defect, you can help to minimize its impact by figuring out how you can eat less, or eat differently. Many very overweight people find that low-carbohydrate diets work better for them. Some people find that metformin and Byetta help them lose weight; others don't.