the person who introduced me to hcg is a fitness instructor at our gym. he did it and continued teaching his high impact cardio kickboxing classes. he started at 275 a little over a year ago and lost 50lbs on weight watchers. he wanted to get the last of it off and diet and exercise weren't doing anything extra. he started hcg at 224 and in 23 days he got down to 195 and looks phenomenal. i beleive that exercising while doing this will help. exercising may increase your appetite but he said it didn't. now he's already conditioned to work out and stuff so maybe it's that if you are working out, you can continue and if you aren't working out, you should wait. 500 cals a day as someone in the fitness industry i can tell you, is hardly enough to sustain a workout since you usually burn that in 1 high intensity cardio session in 1 hour. however, with the hcg and the body's ability to break down stored fat to burn, i just don't know. try it and see. if you feel weak or nauseated, take it down to a lower intensity level or break up the fruit and eat 1/2 an apple for breakfast before you workout. good luck