Your calories are two low for your body weight and your metabolism is going to slow. You can get away with 2000-2500 per day and lose weight. Also protien should be up. As for the hydroxycut. It will mostly increase metabolism to help burn more calories. I do not think you need it but in answer to your question, no, you won't gain weight by stopping to use it unless you increase calories. Once fat is gone, it's gone. Unfortunatly 22lbs in 3 weeks is not just fat. some is water so expect the pounds to slow down and other is muscle. This is bad. A couple pounds a week or maybe a little more since you are big is all you should be losing.

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