i don't know how much you weigh (that makes a difference in calculating weight loss) but i suggest that you just keep at it and only weigh yourself once a week so any ups and downs will not discourage you. there can be many factors: water retention (a quart of retained water weighs over two pounds) replacing fat with muscle or that you are weighing a different times of the day -- sometimes with a full bladder or not having your "daily constitution" just yet. keep at it. if you continue to exercise and take in less calories than you body needs to maintain weight (15 calories per kilo of "ideal" body weight if you want to calculate it) you will lose weight. maybe not a fast as you would like but you will lose. the body loves to gain weight but isn't very cooperative letting it go.
53 & keeping a 1200-1500 calorie diet with 1 hour of aerobics 4 times a week. i haven't lost an ounce in 3 weeks. why?