I used to go to the gym before I started this diet (I was the fat person there!) but I went last week and didnt have the energy for more than 5mins brisk walking on the treadmill, got on the bike instead and 2 mins later... had to go home. I would have usually done an hour on treadmill/bike.
Yesterday I took the dog out for a briskish walk, and same thing.. 10 mins later I had no energy.
I know this diet says not to over-exert yourself when exercising, I imagine we are just no taking in enough calories to sustain a work-out.. a mild walk is about all I can manage till I am finished with this diet.