I mountain bike race so i train quite hard, i am unable to do this diet during the summer months while racing. It is very hard to find the balance so you really need to start off gently and listen to your body. I would recommend that you do low intensity no longer than an hour on ss. Anything above that you havnt got the glycogen that is needed and therefore as your weight gets lower you can be in danger of eating into your muscle mass. This dosnt happen at the higher end as there is enough mins,vits etc in the cambridge packs, but as your weight gets near your goal you dont have the fat to burn for energy. Hope that helps a little.