Even slim fast doesnt recommend living solely off of their product.
Here are some more problems with Slimfast.
Soylent is low glycemic and slimfast and most of the others are high glycemic. I hope you know the lower the GI the better.
According to the manufacturers, a number of Slim-Fast products are formulated with sugar alcohols. Sugar alcohols are a type of food additive that some manufacturers use as a sweetener. Sugar alcohols are not easily absorbed by the small intestine. This can result in flatulence, bloating, diarrhea and a laxative effect in those who are susceptible or in those who consume excessive quantities.
Poor Glycemic Profile
In 2008, the American Dietetic Association published research showing that Slim-Fast and certain other meal replacement drinks do not have favorite glycemic profiles for diabetics. This means that these products release glucose rapidly into the blood stream. This can be dangerous for diabetics, but this news is also relevant for those without diabetes. Obesity plus elevated glucose levels are both risk factors for that disease. Additionally, when glucose levels are out of balance, the body stores fat tissue more readily, potentially thwarting the efforts of Slim-Fast dieters. There is too much sugar in these shakes and so little fiber, that your blood sugar levels are going to go through the roof. It’s pretty dangerous if you happen to be hypoglycemic or hyperinsulinemic. Thanks to the sugar levels high/low jumps be ready for constant mood swings, fatigue, unproductivity, intense cravings and cravings again.
Many Slim-Fast products are heavily laden with sugar. That may be an effective ways to tempt dieters into consuming the product, but sugar has detriments beyond that of supplying extra empty calories. According to Lick the Sugar Habit by Nancy Appleton, sugar can upset the mineral balance of the body, suppress the immune system, cause copper deficiencies, and even weaken the eyesight. Constant exposure to the concentrated taste of sugar also does nothing to train the taste buds to enjoy the more subtle sweet tastes of healthy snacks like apples and berries."