Depending on what part of a person you consider to be essential, King Louis XVI lost quite a bit of weight very quickly.
Multi-vitamins, yeast, some potassium, and long term medical supervision.
An obese person carries a lot of calories on their backs, literally. They key is accessing them without significant malnourishment. With the right vitamins and minerals, a long term fast is just an extreme caloric deficit.
Unfortunately, he probably doesn’t have much chance of keeping this weight off.
Because the way he lost the weight was extraordinary, and not something he can continue from now on. To lose weight & not gain it back, people need to re-learn their eating & exercise habits. Like keeping healthy snacks (baby carrots, celery sticks, etc.) in the house and not candy & cookies. And walking down stairways instead of elevators, and parking your car at the far end of the parking lot. Little things that you can do, and keep doing for the rest of your life.
He likely didn’t do that this way. So while he has got his weight down to a good number, the problem will be to keep from re-gaining it. Hopefully, a doctor is working with him to help him learn effective techniques. Now is his best chance to start new.
I think after 382 days of not eating he’d find it pretty easy to just not eat.
The link I posted said he lost 125kg (275lbs) that year, and five years later he had only gained back 7kg (15lbs).
But even the “starvation diets” that obese people are put on, at least the ones I am aware of, always have some (low) baseline of caloric needs. Usually this is around 400-500 calories/day.
From your link:
This seemed to discuss one man’s success with this recognized-to-be-dangerous diet strategy.
Actually I’m pretty sure he’s lost even more weight via an even more extreme method starting in 1980. He’s now nothin’ but skin and bones. Or I should say, just bones. 
This story says he died in 1990, and was not confined to the hospital, which makes me wonder just how well he stuck to that “fast”. 
:dubious:
NM
Just as an anecdotal data point, after my bariatric surgery I lost 40 pounds in the first month (when I was on a 600-700 calorie/day mostly liquid diet) after which is slowed and I lost 120 over 7.
True. I don’t think this is an advisable strategy for weight loss or safe for most people, even under medical supervision. Nevertheless, a very obese man eating absolutely nothing for a year seems to satisfy the OP’s curiosity about the fastest a person can lose weight. And it’s a very interesting story. But yeah, don’t try it at home, kids.
Note that starvation is the worst way to try and lose weight. Thanks to eons of evolution where starvation was the bigger risk (not obesity) the body has a process to deal with “not enough coming in”. (I’m sure a real medical expert can chime in…) It shuts down a number of essential processes and begins to use as little calories as possible. As a result, that stored fat will be burned a lot slower than the anticipated 2000 calories a day. Plus, as starvation proceeds, all your muscle mass - which burns extra calories just being there - gets absorbed by the body to also reduce calories needed. Sometimes this includes the heart muscles, which is one reason why people on crash diets risk heart complications - and any seriously intense diet needs medical supervision. People on a habitual low calorie diet, even if not so intense, tend to have difficulty with weight loss because their body has gone into that “survival mode” and allows itself to get by on minimal calories.
Allegedly, the best weight loss regimen was moderate calories and more exercise. Which also made you healthier…
(This was the point of the Atkins diet and similar - the contention that it was consuming carbohydrates that determined the rate of fat burning, while a lack of protein triggered the starvation response; eat only proteins - and fat - and the body would consume fat reserves for the rest without going into starvation shutdown. AFAIK, this has never been concisely proven but the fad diet world seemed to take it to heart.)
I’m pretty sure the skin’s still there. :dubious:
Couple starvation diet with acute influenza, or cancer, or hyperthyroid storm and maybe lose lots. Without something medical causing abnormal metabolic burn?
But very low calorie diets (VLCD), meaning 400 to 800 calories a day, which I think qualifies as “starvation diet”, have been well studied.
Short term (4 to 6 weeks) VLCD can result in 1.4 to 2.5 kg loss per week, but over the course of 16 to 20 weeks it still averages out to 0.7 to 0.9 kg/wk.
Calories out is not a constant and the body adjusts in response to the change.
A pound of fatty tissue is not all fat. Others have mentioned water weight. However, from random googling I’m seeing that adipose tissue is only 10% water.
I’m all for healthy skepticism but he was monitored by doctors aregularly nd he did lose the weight in the time reported. If he did slip, it can’t have been much or often, so the accomplishment stands even if we find out he had a burger in there somewhere.
The show naked and afraid is pretty much a starvation diet. Weight looses usually range up to about 24# for women and 32# for men in 21 days of near starving.
I’m a bit confused at how slowly people think weight can come off. When I wrestled, I generally lost 2-3 pounds in a 2 hour practice (weighing only about 150 pounds). In a pinch, I’ve lost nearly 10 pounds in a day to make weight. Not healthy, not sustainable, but doable (it certainly does suck, though).
The bigger guys (200 pounds+) could sweat out 7 pounds in a practice (and make fun of the smaller guys… they were allowed to eat because they didn’t need to fight to make weight). And then when we’d run laps after practice, the smaller guys inevitably slip and fall in the puddles of sweat they leave on the mat. Not pleasant.
It comes down to the exercise component. Work hard, lose water weight, burn fat and calories, sacrifice muscle at times. Again, not a recommended regimen; but it’s possible.
I can’t believe that, on a board dedicated to fighting ignorance, no one has yet mentioned the fastest way of losing weight: go into free fall. Orbit would be a good long-term option, but jumping off a tall building would work too, temporarily. Instant loss of all weight.*
Losing mass, on the other hand, is trickier. 
- Please read terms and conditions before jumping. Not covered by most health insurance.
That’s nothing, I lost 500 pounds in one night. I’ve really got to be careful in British casinos…