Hello, I was wondering what could cause excessive weight gain. Pretty much over night I gained weight i'm talking 3 to 4 sizes. I have extreme constipation and sometimes do not go for a week or two at a time. I was wanting to know if bowel problems could cause me to gain. Also what are some other things that could cause it. I know over eating isn't the cause so I was considering going to the doctor and was wondering what tests might be run to find out what is wrong with me.