Photo gallery: 6 ways to keep the weight off

2. Change up your fitness routine

Regular exercise is key to staying healthy and fit -- and to fending off weight gain. But it's easy to get bored with your exercise program, especially during the colder months, when you may not want to go outside. Change your routine regularly -- with the seasons, if possible -- and keep trying new sports and activities. Maybe this fall will be the right time to take running seriously, in time for a charity 10K, or perhaps this winter you can start a martial art. Keep exercise fun -- and social, if that's your thing -- and it won't become a chore.