No, three meals a day is not too much - I hope I didn't unintentionally imply that you should skip meals. However, in leading groups of beginners, I often see them bring far more than they can eat (or bring heavier food than necessary.)

The only way to know how much you need is to take what you think you need, then go out and see if you have any food left at the end of the hike - or if you didn't take enough. The suggestion about starting with a public campground is simply to avoid hiking out hungry if you guess wrong.

I'm 5'10" and about 185 - and 66 years old, which is also a factor: I manage about 8 - 10 miles a day, and probably don't burn as many calories as you (I'm guessing you might hike farther in a day?) So, I don't need as much food as you might.