Ana, I am a personal trainer, and can tell you that by losing weight within the first week, this weight is easily put back on. Don't get excited over the first week, yes it is only water weight. Speaking of water, how much do you drink, at least 8 glasses a day is recommended. This is the hardest thing for everyone on earth to do... but you have to make the effort. The long term weight loss comes over time. THis happens when you lose your flab, and turn it into lean muscle, through exercise. Good luck!!!