Why Perimenopause Weight Gain Happens Perimenopause weight gain can feel confusing and discouraging, especially when the habits that used to work suddenly stop working. There comes a moment for so many women when they look in the mirror and think: “What is happening to my body?” The weight gain seems sudden.The bloating feels constant.Sleep gets lighter.Energy gets lower.The brain fog creeps in.And the things that used to work… suddenly don’t anymore. You try harder.Eat less.