I've been on it a couple of times. You can lose weight fast, but the downside is, like with any "diet", you put it right back on just as fast.Go to their website http://atkins.com/ click on "Atkins Nutritional Approach" then click on Phase 1. That's the phase where people drop weight fast...it allows a maximum of 20 carbs per day. You have no idea how many things you have to cut out of your diet, to keep it to under 20. You practically live on meat, cheese, and a few vegetables.Just remember, it's not a healthy diet long term, and the weight comes back easily when you start eating carbs again.Best way to lose weight is to eat a healthy balanced diet, drink lots of water, and exercise regularly. Sometimes we need a quick fix for a special event though, but it gets tiresome losing the same "X" pounds over and over. I'm doing that now...working on losing 15 lbs of the 20 I gained back during the last year after I got off of Atkins. I lost 35 on the diet though. LOL!Good luck!