How long are you sleeping, just out of interest?
For me, long, deep sleep that leaves me waking up refreshed is a sign of good health. The more active I am, the more sleep I need.
I wouldn't be concerned too much right now. It could be that your body is busy doing some healing or other restorative work that wasn't possible with your previous diet. Or maybe you weren't sleeping enough before. If you start needing more than 9 hours to feel refreshed without being active, or you start feeling unrefreshed no matter how long you sleep, then I would start to look at possible causes.