I did my first juice fast in March for three days. It was CRAZY DIFFICULT and awesome at the same time. I eased into my fast with a few days of raw foods and eased out with a few days of raw foods which was also difficult but I recommend it. I really felt cleansed and renewed after the 8-9 days of this.
It helped with my weight loss by practicing mindfulness when eating. I felt like I was able to kind of restart... if that makes any sense. I drank as much juice as I wanted and tried not to drink too much fruit juice to avoid sugar spikes. It is also not recommended to do any strenuous physical activity while on a juice fast. Yoga and walking are probably the most intense you might want to go.
I lost 6 pounds on my fast but gained back 3 after consuming regular solid foods again. I did a ton of research before I started, so if you have any other specific questions let me know. GOOD LUCK! Message me if you need support throughout your fast, like I said they can be CRAZY