Is it really true that people tend to gain more ...

It could be true because people tend to eat heavier foods in winter, do less exercise outdoors and fail to monitor their bodies because of all the layers of clothing they wear.

In addition to the reasons given above, I think our bodies naturally make us gain weight in the winter time to create an insulated layer to protect us from the cold. Our mood is affected by the low temperatures and the decrease of sunlight, triggering our appetite for foods high in sugar and fat content such as chocolate that help produce endorphins(the happy pills:o)

I've heard that too.I guess because the holidays make people lazy and the cold weather makes us crave comfort foods.Personally I lose weight in the winter.I work out constantly to stay warm and keep my sleep cycle regular.Because of the cold I don't run around in the yard with my dogs,so I need another way to expel my energy or I won't sleep!