This. I had a health issue this summer that stopped me from riding for 5 weeks. I decided to radically change my diet and dropped that last 10 lbs that I just couldn't loose through cycling. When I got back on the bike I hadn't lost much fitness and it was just a few rides untill I felt I was back. Eat well ( and probably less) during down time or its a double whammy. Now, if you're one of those naturally skinny people then you can disregard this, although eating right usually makes you feel better regardless.