Why babies get fat

The NY Times reports:

Babies whose mothers smoked during pregnancy are at risk of becoming obese, even though the babies are usually small at birth.

Babies who sleep less than 12 hours are at increased risk for obesity later. If they don’t sleep enough and also watch two hours or more of TV a day, they are at even greater risk.

It seems unlikely to me that these things really cause obesity. Maybe it is a simple matter that those who do not follow health guidelines tend to smoke and get fat, but there is no direct relationship between a mom smoking and a baby getting fat. There could also be genetic reasons for a correlation. I expect that official health guidelines will list these things as causes of childhood obesity, but they are more likely to be spurious correlations.

New research indicates HFCS may be causing obesity:

When rats are drinking high-fructose corn syrup at levels well below those in soda pop, they're becoming obese -- every single one, across the board. Even when rats are fed a high-fat diet, you don't see this; they don't all gain extra weight.

That quote is from a psychology professor. I would think that medical researchers could figure stuff like this out, but I guess they are too busy doing retrospective cohort studies.