maybe sad isnt the trigger for the weight gain, they've got to that weight for some reason either health, not self motivated or dont have the friends around you to motivate them or personal reasons like having kids. the new the daily routine change means they are not the lady they used to be and dont have the time to burn it off. for example having kids amazing as it is, changes the personal time they used to have to themselves to go the gym or take part in sport. magazines and tv shows probably dont help.
maybe seeing other women doing things they used to do and be makes them sad. not being able to fit into the clothes on the wadrobe.