Detoxing is just another word for cleansing. The aim of any detox program is to boost the efficiency of the digestive system. It should stimulate the parts of the body that cleans and eliminate toxins. Detoxing will improve the underlying health making a person less prone to be sick. Using a smart detox program can be great for sustaining great health.
As a fitness professional, I am not certified to offer advice on nutrition. I can give facts to my clients, but not opinions on supplements or nutrition programs such as the one you’re discussing. I think you’ll find that unless a fitness professional is a registered dietitian or has a medical licence or certification, that fitness professional will usually advise a client to discuss such matters with a physician before undertaking such an extreme program. I know of no “detox” programs available that are not harsh on the body.