Okay. Here's the take of someone who sorta kinda actually tried this crap once...
Away back when, the squadron commander gave me the straight scoop, as in "You will make the weight limits the Air Force prescribes for your height by the last day of January, or on the first day of February you will not sew on that third stripe." Seeing as that meant no NCO status, I buckled down and did one of the dumber things I ever did.
Daily intake: 500 units of Vitamin E, 3 One-A-Day brand multivitamins, and 45mg of Dexedrine a day (this was back when they prescribed it as an appetite suppressant -- and I'd built up a handy little stock of it, legally I might add), and all the water I could drink.
Additional weekly intake: Saturday night, 6 pm, up at the Jet Stream when Star Trek came on channel 50 out of Detroit, two Polish sausages on hot dog buns, and a mug of beer.
That was it.
I sewed on the stripes, having lost 32 pounds in 31 days. Doesn't matter that I waited too long to find a bed one night when them pills wore off immediately...they found me in the hall, on my knees with my head against the door, sound asleep, and the key was in the lock...
I was younger and stupider back then...and that will be enough of the "Whaddaya mean 'back then'" garbage...
So, on the basis of personal experience, anecdotal as it is, I have to say to anyone that claims of living off water and sunshine (h*ll, I'll be generous and let you throw in a triple handful of vitamins and supplements) are highly suspicious, bordering on outright fraudulent.
Translation: I remain unconvinced.