Nutrition, Joeman, that has to be the start of it.
Don't ask your body to carry you around the footie pitch like a trojan for 90 minutes if you're only gonna give it Coke and burgers (please, I'm not assuming - just making a general point).
I could bang on and on about yer 50 grams of protein daily, green leafy veggies, no saturated fats yadah yadah yadah, but a much easier way is to check out some books by Adelle Davis.
I found 'Let's Eat Right To Get (or is it 'Keep?) Fit' in an old bookshop a few years ago. It was first written in 1958 I think, 'updated' in 1970 for my version, but I know there have been updates/reprints and the like and plenty of titles are available in North America, where I think she comes from.
Even then it was very critical of the direction being taken by the general North American diet. F**k knows what the more recent updates say.
Anyway, she goes into great detail about what foodstuffs are gonna give you what benefits (including some pretty remarkable ones), gives evidence, research, case histories and basically all the info (I needed anyway) to plan a healthy, nutritous diet. Doesn't have to be boring and/or taste like shit...
Then I began to wonder 'why IS all the bread I can buy now white and full of additives?', 'why IS there flouride in my water?', 'why HAVE all the good old basic foods (natural peanut butter, genuine wholegrain bread, unsaturated oils etc) all but disappeared from the shelves?'
Yeah, of course I'll find a conspiracy in it, but seriously chap, just from buying a copy of that book I am now a static 66 kilos (sorry, don't do pounds any more), at 5' 10" (ah the English, we don't confuse our systems). I do little exercise, smoke, occasionally drink, eat more or less wtf I like when I like, but know enough to avoid anything processed, packaged, McDonalds etc.
Oh, and I'm veggie, but that is for my personal reasons and zero per se to do with nutrition, other than I don't want CJD for Xmas.
Let me know how you get on