At this point I have helped 4 adults (3 being 60+ yrs old) and myself try the diet. Even my own father.
Most can't do all 90 days for whatever reason. Every single person that has tried it for 30 days has lost about 25 lbs. The ones that tried it for 60 days lost 35-40 lbs.
Two of the seniors had blood tests done before and after the juice diet, both showed improved markers on EVERY single thing tracked, including blood sugar and A1C levels, even though they basically lived off the sugar in vegetables for 60 days.
Every single person agrees that vegetable juice plus meat would be the ideal diet for them long term after trying it.
Even with all that said, new people that year it says it doesn't sound healthy. If you told them your diet is 2-3 lbs of salad plus meat a day, they'd say ya that sounds healthy. If you tell them, hey, have 10 lbs of salad a day for 90 days, they'd say that sounds healthy but sounds too hard to eat that much. If you tell them, sure, why don't you juice it instead and make a gallon of juice, they'll say that doesn't sound healthy.
I think weight loss is very simple. It's just not easy. And it's not easy to decide to try. I begged my dad for 3 years to try 90 days of juice, after I tried. Finally he tries it, and is now a believer. My mom though, seeing his great blood test results, and seeing him lose 35 lbs and feel great, still isn't convinced she could give up pastries and bread and just live off salad (juice) for 90 days.
Heck, people will try hormone altering drugs before they try celary, carrot, beet, cucumber juice.