I use to feel this when I was younger. I would gain about 30lbs every winter and never feel like getting out of bed. However, not so much for the last couple of years. I don't know if I grew out of it or if its do to my weekly routine... of working rotating 12hr shifts Days/Eves/Nights, lifting weights for 2 hours 2 times a week, and drinking energy drinks all day long everyday.