It's basically a way to regulate your calorie intake. I do not like all of the ingredients in Slim Fast. The hard thing is finding a diet that you can stick to. The best results happen when accompanied with (moderate) exercise. If you really want to have an impact, give this plan a try -- https://dietdynamo.org/the-mayo-clinic-grapefruit-diet/. It takes a few weeks to start seeing and feeling results, but it is sustainable and it works.