They were comparing people who sleep 5 hours a night or less with 7 or more.

Most of us need 8-10 to be properly functional. It is easy to train ourselves to "need" 6 or less, but we become constantly impaired if we do so. The first effect of our impairment is that we do not realize how impaired we are, but other people in our life can see it, and it shows up on ability tests.

Therefore I'd summarize this by, "People with severe sleep deficits put on weight faster than people with mild sleep deficits." If you're actually getting enough sleep, I'm not sure what conclusion I would draw either way.

Cheers,
Ben