Agnostic and atheist aren’t mutually exclusive things. 99.9% of atheists are agnostic about there being a god because it’s unprovable. Same way you’re likely agnostic about Russell’s teapot en.m.wikipedia.org/wiki/Russell's_teapot
It’s your genetics. I’m the same way. Can eat basically anything. At my absolute heaviest I was 5’11 165lbs, which is heavier than I like to be. But I just cut out the 10 sodas I drank a day and lost the 10 lbs I wanted to in like a month.