You're either weak or fat. Work on it.
Or just a really big dude naturally, but u can still work on it.
OK to make it simple I will omit any climb that I consider a 'mountain' and post the toughest 'hill' in my area:
1.72 miles,
10% grade with almost no variation.
It's a good hill to test yourself on or work out on because it is so consistent.