I Am Fat And Out Of Shape

My dad has been forcing me to go on walks with him. Well, he jogs, I try to jog for a minute and a half before giving up and walking. He tells me I'm out of shape all the time and that "we have to get me to a gym and shed that belly". It hasn't been working. Also the p.e teacher at my school told me on the first day of school, that I had "filled out". Everytime he sees me he gives my belly a pat and asks if I'm taking any p.e classes because I "need to get some exercise".