Starting with the bad, the first weeks are when you are likely to suffer the most aches and pains. I had yet to lose sufficient weight to really enjoy exercising until two weeks had passed. Even after two weeks occasional stomach aches and wobbles may be felt. I recall after around three weeks doing an enormous poo and my lower abdomen felt bruised and ached all morning after that.
On the other hand, as time passed my energy and mental acuity increased. I spend less time on the computer, and more time in the garden. I rarely watch DVDs before going to bed, and sleep earlier. I wake early, at around six, when I do some of my best writing, or work in Photoshop, then as it gets light go out for an hour’s gardening.