I’ve never met someone with a weight problem who didn’t know why they had it. Sometimes it’s eating too much, and sometimes it's not enough exercise, many times it's both. Some folks are sweet "freaks;" others salt and snack food "junkies." I’ve noticed these "either/or" patterns in people I’ve worked with.
Of course, family genetic history plays a part, but it’s also a number of other things: habits, poor behaviors, boredom, self-hatred, emotional rescuing, etc.
Are you someone who just has big portions? Do you love food more than anyone or anything? Do you love food more than you love yourself?
What’s the reason you’re overweight? Define it, and then surrender it to God, asking for help. I'm living proof that help will come. Check with your doctor, too.