Holiday Weight Gain Studies Studies are very mixed on whether holiday eating causes weight gain. The Good1 In several studies over the last thirty-one years, subjects gained approximately 3/4 to 2 lbs. during the holiday season However, in one study participants felt they had gained 4x as much weight as they actually gained Two other key finding: Although the amount of weight gained between the holidays was small, it represented the majority of the weight gained for the year ...