Personal note: I've been following this diet since Jan 1. I also run ~ 70 miles/week. I've run 3 of my best marathons this year and lost 5 stubborn lbs (145 -> 140, I'm 5'8"). There are other styles of intermittent fasting. I'm enjoying this way of eating.
Aside, a related BBC/Horizon documentary I saw years ago flipped the question of obesity on its head and asked: Why Are Thin People Not Fat?
Looking at 5:2 simply as a "pattern of eating", however, makes it easier to consider not only the apparent health changes but also other potential benefits, including:
- Reduction of IGF-1 - Prolonged period of not eating as a means to promote cell repair - Shining a light on the cultural norms around eating three square meals a day with/without snacks in between.
After watching the documentary it seems like 5:2 may be more than just another "fad" diet.
And the subsequent discussion on HN: https://news.ycombinator.com/item?id=10863626
In my case if I have to do it, I'd rather pay the price the first day, then keep the momentum. Also the third/fourth day there is a payout as you get a nice 'mental high'...
And blimey, the friday evening you can eat anything and it'll taste heavenly :-)
Right now, alot of dieticiens are still behind the research, but they're slowly getting caught up.
Even the new york times published an article admitting that breakfast was not the most important meal of the day. they showed metastudies that showed there was absolutely NO evidence that showed breakfast was better for your health (other than some correlation based studies). It's time to jetison breakfast and live as our ancestors lived - the way we evolved to live. Nobody back then ate 3 meals a day - this is a new phenomenon started recently within the last several hundred years. the roman army conquered all of europe on just 1 meal a day: called lunch, and they got more excercise than any of us. And before that, people ate infrequently because the food supply was so unstable, often going for days without food.
Non the less 2:5 sounds cool; please come back to report your experience! :)
Then it's occasional fruit juice in the morning (bit of an energy boost) and coffee only until the friday.
It's a lot easier than it sounds, the 'key' thing is preparation; pick a week were you don't have a lot of 'social' to do, or any heavy physical things planned, and near empty fridge is good; instruction to the family not to decide to cook your favorite meal during the week and so forth.
Otherwise it's as reported; hunger on the first day mostly, then nothing; you get a bit of a metallic taste in the mouth, but tolerable... You get what I only can describe as a 'high' on the third/fourth day.
I lose roughly 1Kg a /day/ with that method, so if you do it once every quarter or so, that's largely enough to make up for some the odd chrismas/party/easter and so on :-)
However, one time I tried to go for three days, and on the third day I got suddenly extremely lightheaded while hanging out with friends, and it was a scary enough that they insisted I end the fast right there (I agreed). My enthusiasm for fasting was tempered quite a bit after that.
Maybe that wouldn't happen the next time I tried going 3+ days, but I don't want to risk it.
Also, I've noticed that driving any serious distance while even on the second day of a two day fast, or concentrating on hard programming problems, can be pretty difficult. That's the main reason I don't do it much anymore (I was in high school and had nothing better to do when I was fasting before).
The body is more than 50% water, so weight is highly variable based on water retention, and fasting causes the body to excrete a lot of water.
For one, no salt intake will cause you to lose water. Secondly, glycogen depletion also causes you to lose water. The metallic taste in the mouth is ketosis, proof of glycogen depletion.
I did it just for fun but noticed significantly improved productivity during the week.
I too would drink juice in the morning and possibly juice or 2 sugarcubes at lunch but not always and no calories otherwise.
To ease into fasting I would start by skipping dinner. Skipping breakfast was then easy (for me at least) and the rest of the week was no problem.
Then during a boring week in the military I decided to test what I had heard that we have 80% left when we feel completely exhausted. So after a couple of days of my "normal" fasting (IIRC) I skipped even my breakfast juice and continued without. Later that day I went to the gym and started lifting weights. 15 minutes into that I was completely drained and I was shaking for hours afterwards (again IIRC). That was my last time. :-/
I want to try again, but with a family it is way harder (and that experience kind of scared me.)
In this case: body/mind hacking.