What causes weight gain during menopause? if hormones are replaces (hrt) does this counteract some of the gain? i still exercise/diet but cant lose

It's complicated: I don't think we have a definite answer. Certainly metabolism changes with age and the body becomes more efficient at making and storing fat. Genetics, diet, and exercise are factors and the hormone changes of menopause contribute but simple replacement is not usually effective. There may be a role for testosterone supplementation, which is available but outside FDA approval at this time.