Winter weather is a big reason why people put on weight in colder months. Not all of us can afford a gym membership, leaving us to fend for ourselves as we try to walk or run in the elements. While there are other indoor options, like yoga, Pilates and home gyms, many people with modest exercise schedules simply abandon the practice when it turns cold. Winter also means shorter days, which don't lend themselves to getting out on the sidewalk or hiking trails. When darkness and cold have arrived before you get home from work, only the dedicated are inspired to get out and burn some calories. Residents that live where the climate is warm year-round have an easier time, but much of the United States suffers through moderate to severe weather conditions during the winter.