Thanks to blue1 who found the original paper (http://www.cell.com/cell-stem-cell/fulltext/S1934-5909%2814%...), I found this in the comments section: "In this study, the mice were allowed to drink water, but no food was allowed. In general, when limited food & water are allowed, the protocol is referred to as a "fasting-mimicking diet""

So no food, but water was allowed.

Just remember the context: the mice were subjected to chemotherapy schedules... so it's not like "hey take healthy mice, fast them and see them get healthy", but more like "hey take healthy mice, fast them, subject them to chemotherapy, and look... their immune system responds better than if we allowed them to eat pre-chemo" (apologies if I summarised this wrong)

That paper isn't the original- it's a followup. The original is a strict fast (water only) for 72 hours.

The FMD (Fasting Mimic Diet) is for 120 hours (5 days) and has more food allowed:

"The human FMD diet consists of a 5 day regimen: day 1 of the diet supplies
1,090 kcal (10% protein, 56% fat, 34% carbohydrate), days 2–5 are identical in formulation and provide 725 kcal (9% protein, 44% fat, 47% carbohydrate)."

Wow, that's lower than what many calorie restriction experimenters run!

Yeah, it's supposed to "Mimic" a fast. Supposedly it's easier to do than the 3-day water only fast, since you're getting some sustenance, but I haven't tried it.

About 3 years ago, I undertook a water fast that lasted about 17 days. It does take a lot of mental preparation. Nutrition wise, I ate only fruits for about a week before the fast. The first few days were very hard, but then I simply did not feel hunger at all. I intended to continue the fast for 30 days. But from about the 4th day onwards my mouth started having an awful odour and my tongue had a thick white coating that was the source. Into the third week, I simply couldn't bear that smell anymore and gave up. for getting back to regular food, I did the same thing and had only juices and fruits for about 3-4 days.

Now, I'm not an expert, but I read while preparing for the water fast that your body has nutrients it needs to survive for a few weeks. I didn't take any supplements during that time. Unfortunately, at that time i didn't have the means to measure and quantify what changed after the fast. I do remember being in a great mood for a few days after the fast. I don't know how much it benefited me, but it was an interesting exercise

That odour is probably the ketones coming into play when the body starts using fat for energy, instead of carbs or protein. And yes, it's a well known fact.

For 3 weeks straight would be unusual though and not explain the commonly occurring tongue coating.

Sounds more like lack of immunity and candidosis.

You still have to brush your teeth when fasting. Scrape all that plaque biofilm off your tongue. Plaque bacteria feed on all sorts of nutrients in your mouth and in your saliva, not just food residue.

It is not like I didn't brush my teeth. But the layer on the tongue was about 1mm thick, maybe more, and no amount of brushing it would remove it. It would only make my tongue hurt after a while, so i went back to regular brushing. Ketones may be the answer as the other reply explains, but one thing is for sure, having that foul smell in my tongue and nose at the same time 24 hours a day for 2 weeks is no party.

Of course the fast means little if you went back to your usual diet. The key is to have it rejuvenate/regenerate/heal your system, then to break it, but by transitioning to a better/cleaner diet (blended (Vitamix'd) vegetables, lean meats, nuts, and cold-pressed organic oils, for example).

Also, you can add in intermittent fasting (eating within the same 8-hour window each day) and mild caloric restriction (calculate your actual daily caloric requirement (more involved than it may seem), then eat 80% of that).

Then there are the supplements and nootropics. After a water fast is the perfect time to take on the habit of supplementing (in addition to continuing to consume mainly blended vegetables) with things like Acetyl L-Carnitine (and other free-form amino acids), CoQ10 (if you're over 30), Astaxanthin, Ashitaba, Vitamin D & K, Magnesium, (Opti)Zinc, etc. Also, there are nootropics like Cerebrolysin (one month every quarter), NSI-189 (also one month every quarter-- maybe after Cerebrolysin), and (N-Acetyl) Semax (Amidate) + N-Acetyl Selank (also one month every quarter-- or two months if you can't source NSI-189). There's also fasoracetam + coluracetam, Tianeptine Sulfate (mainly if you struggle with depression or anxiety), and many other things.

https://news.ycombinator.com/item?id=12386378

https://www.reddit.com/r/Nootropics/comments/4z4t1q/top_5_an...

You can also look into Oil Pulling (unless you have many fillings).

If you have regularly eaten well for some time before (i.e. no junk food but real food) you probably (?) have a sufficient store of nutrients to keep your system running for 72 hours.

The important question to me: Does drinking coffee (black without sugar naturally) blow the supposedly positive effects of the fast?

As a coffee addict and someone who fasts I keep looking into this. Strictly speaking a fast is supposed to allow a period of detox for the body so coffee isn't really a good idea.

That said it doesn't break your fast since it has a trace calorie content (provided no milk and sugar). After all some proponents of fasting recommend water with lemons or apple cider vinegar (for killing bio films/candida effects). I can't imagine coffee would be that different to lemon water calorie wise.

Pros and cons - if no coffee makes your fast unbearable have some (I always do), but ideally you're looking to consume only water.

>Does drinking coffee (black without sugar naturally) blow the supposedly positive effects of the fast?

I don't think so, but I'm not professional. The caloric content of black coffee is negligible.

> Does drinking coffee (black without sugar naturally) blow the supposedly positive effects of the fast?

I curious about this and the effect of zero calorie soft drinks.

It's not that hard. If you're going to do three days you might as well do a little longer. It takes around three days to switch to ketosis, after which hunger disappears. I did a week with just a sense of determination and knowledge of what to expect, and my relationship with food improved immensely.

It's even easier if you eat a ketogenic diet already.

There is a lot of evidence that the human body can survive for much, much longer than 72 hours without food:

http://www.scientificamerican.com/article/how-long-can-a-per...

http://www.bbc.com/news/magazine-17095605

The first article mentions someone going for 73 days without food, the second 66 days, and many others for shorter periods (but still on the order of multiple tens of days).

Some examples:

"In the 1940s, Mahatma Gandhi survived 21 days on sips of water during a display of civil disobedience."

"Dr Mike Stroud, senior lecturer of Medicine and Nutrition at Southampton University ... who accompanied veteran British adventurer Sir Ranulph Fiennes across the Antarctic, said it was possible to survive 60 days without food."

"In 1981, Republican prisoner Bobby Sands died in Northern Ireland's Maze prison after a hunger strike lasting 66 days."

Of course many factors may influence how long you can go without food, such as the amount of physical activity you engage in. If you're running marathons every day, you're naturally not going to be able to go without food as long as someone who's immobile the whole time, etc.

Fat people can fast for a year with few problems.

Here's a write up from the NIH.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2495396/pdf/post...

Overeating is a psychological disorder. Few Americans would have any ill effects not eating for a few days -- especially the 66% of Americans who are obese or overweight.

I suppose not, but the lack of specification which method of fasting was used is the most glaring omission in this piece.

see my comment above: "In this study, the mice were allowed to drink water, but no food was allowed"

Thanks for taking the time to drill into the study. It's just disappointing that the journalists apparently didn't have the time (or didn't consider it relevant).

Probably there is some minimum, because when you drink just regular water that has some calories as well. And not drinking for a day might be he worst dietary idea ever.

UPDATE: Water doesn't contain calories. Sorry for the misinformation.

My mouth (actually my hands) was faster then my brain. :-)

Please explain where the calories in plain water come from.

According to mass-energy equivalence, every gram of water contains ~2.15*10^13 calories.

So where can I sign up for having my stomach replaced with a matter-antimater reactor or whatever it is this gadget that actually gives me access to this energy?

I think you're missing an algebraic sign there.

I assume you are talking on the physics e=mc^2 type level rather than an energy store that can be metabolized by your body.

If regular water has calories in it, then I would not be willing to drink it. ;)