I suppose that is possible. Are you sure of the cals you burned? Maybe I am a light weight (ok I know that I am!) but I don't burn that many calories in during my average work out. I have been logging what I eat and exercise while working with a nutrionalist and exercise physiologist. We figured out my Basil Metabolic Rate and the additional calories I would need if I exercised X amount during the week. It was really interesting and helpful. She did warn me not do eliminate more than 500 calories in any one day. You need 3500 cal deficit to loose 1 lb. ( I aim for that every week).