There are a lot of people who started running to loose weight. I am one of them. I came across an article, in Running Times by Rachel Toor, talking about the issues of weight and running. Rachel Toor describes reading a biography, Seabiscuit, where carrying an extra pound or two can handicap a 3,000 pound horse.
Everyone has heard you are what you eat. I know when I eat like crap, I run like crap. Weight loss, for me, did make it easier on my knees and back. In my home, we all eat the same foods. It isn't called dieting, it's just what is for dinner.