Diet and lack of Sun Rich. And definitely need more excercise.
Eat more fruit and fresh veg. Try not to eat too many simple carbs, especially snacking before bedtime. Dont eat chocolate, and try to avoid caffeine. Get more protein.
Take 12 fish oil per day.
http://www.hollandandbarrett.com/pages/product_detail.asp?pid=146&prodid=581&cid=17&sid=0^^ That fish oil.
Eat a breakfast that isnt high in fast burn carbs (in other words a crappy cereal). If you must eat cereal, make sure its decent oats. Always try and get plenty of protein for breakfast. Your body will start to burn excess carbs and fat stores. If you cant get protein, try and drink a fresh fruit smoothie. Bulk up with some natural fat free yoghurt and some milk.
Get a nice lunch thats high in protein and also got some vegetables. I eat a lovely omlette for lunch (not practical for everyone - but im lucky enough to get home for lunch). Or if you cant, then a decent meat salad with chicken or tuna.
All i eat for dinner is a decent piece of meat and a side salad or vegetable portion.
I feel fantastic every morning i get up. Even when/if i have a cold which is damn rare.
Always remember that good prep with food is the best way to stick to a good lifestyle. I try and plan my meals a week ahead.
I used to be a total gym rat as well, but just dont get the time these days. Walking the dogs, MTB and running are all the excercise i get. The Mrs likes to get me jumping about in front of the TV like a loon to some high impact aerobics as well. Also bedroom olympics are a great form of excercise!!! Get as much of that as possible.
One last tip. This is one i struggle with. Get away from the laptop/pc a few hours before you go to bed. The light that is given off by the screen actually makes the mind more active. Its similar to a light given off by the spectrum of the sun (IIRC), which prepares the body for excercise. It can cause restlessness in bed.