The average Thanksgiving meal has around 4,500 calories, or about twice the recommended calories for an entire day. If you eat well and exercise all year, one day of splurging is not a big deal. But Thanksgiving is the informal start of the holiday eating season. Between Thanksgiving and New Year’s, adults can gain up to 10 pounds. Here are some easy ways not to overdo it this year. Have breakfast and lunch before the feast. Eat slowly. Cut down on alcohol, which has tons of calories. And throw away or give away the leftovers.