Your symptoms sound like hypoglycemia. As someone for whom hypoglycemia is a chronic issue, the best thing I've found for dealing with fasting is to load up on protein-heavy foods with low glycemic indexes prior to the fast.

Edit: I should be more clear - avoid foods with high glycemic indexes prior to the fast. In fact, just avoid them generally; they're usually empty calories.

A good test for whether you're hypoglycemic is to set an alarm to go off every waking hour for three days, and eat a handful of nuts (or something else with a low glycemic load) every time the alarm goes off.

I did this and felt waaaaaaaaay better than normal mood- and concentration-wise. Realizing that I have blood sugar issues is the most important thing that's happened to me in the last five years except for having a kid.

Wait, but what's the test condition? What results should I expect from your experiment if I'm hypoglycemic or not?

Right, sorry. Basically that you feel way better, unmistakably better (mood, concentration, alertness, that sort of thing). Not super scientific, but effective at least in my case.

I'd recommend something different, and drastic.

At Wal-Mart, they sell a glucometer called ReliOn. It's the cheapest strips of the ones out there, 50 for $21.

Start testing your blood sugar. Test it when you wake up. Test before you eat, and then 30 minutes after you eat (up to 4 tests) and look at the carb count on what you ate.

A healthy human should be between 85mg/dL and 100 mg/dL. Numbers over that show "something". Over 140mg/dL causes nerve death. We think that over 100 mg/dL causes pancreatic beta cells to die or mutate.

Then start playing around with how much carbs you eat. Dow what's called, "Eating to the Meter".

Also analysing what you're eating may give you a strong answer why you're feeling bad by 11.

Also, look in my history for what I'm doing (from yesterday).

I copied my technique from this BBC doc: http://www.documentarytube.com/videos/eat-fast-and-live-long...

On my fast days (Tues/Thur/Sun) I eat a decent breakfast, but I don't pig out. Then I just don't worry about food until breakfast the next day (when breakfast tastes particularly delicious btw).

To be honest, the biggest factor tied to failure for me is mood. If I'm in a poor mood, I'm 1000% more likely to feel like I can give in and grab lunch on a fast day. And then once I've had lunch...

The next biggest challenge is other people, especially on Sundays. I might eat fruit salad at brunch, b/c it's both hard and weird to not eat in the company of eating friends.

One thing I try to keep front-of-mind is how awesome it feels to wake up in the morning after a fast day with a sense of accomplishment. And how satisfying it was to need to take 2-inches off the waist of the suit I got married in. Success is addictive.

Edit: I allow myself as much coffee/tea with milk as I feel I need. Yeah, it's not fasting, but it's not eating either.

>Success is addictive.

Be careful not to go too far then.

IF is by definition just about constraining your food intake to a certain window of time. Most people do this later in the day out of necessity or habit (e.g. 2-7), but there's no reason your window couldn't be 6-10.

The downside is that you are much more likely to cheat if you do this, because now you have to go all afternoon and evening without eating, and then go to sleep. Psychologically it's much easier to wake up and be able to say "only 6 more hours to eat" and go to bed a few hours after your last meal than it is to eat your last meal, have 12 waking hours left, then try to go to sleep with a grumbling belly.

Edit: A lot of people practice IF without even realizing it. The most popular form (mentioned in rob_61's linked article) is 16/8. If you don't eat until lunch and don't do a late dinner, it's very likely you fall in the 16/8 window.

Here is the best summary I've seen on IF...

http://antranik.org/intermittent-fasting/

btw, I've been practicing IF for 2+ years and love it.

I've done IF and lost 40 lbs with it. My advice is to eat something really small, and see what the smallest breakfast you can get away with is. After a month or so, try stopping breakfast and see how you make out then.

My understanding is that the gut and vagus nerve are very sensitive to disruptions, any changes in routine have large initial perceived effects, until a new equilibrium is established. I think this mechanism is why diets are so faddish and people think they have food allergies when they actually don't.

So, mitigate the worst of the symptoms, be willing to accept some temporary discomfort, and iterate towards a better diet over time.

Maybe it helps to be a bit heavier. I used to almost faint without breakfast and running to catch the tram, but I gained a bit of weight (back into normal range) since then and now I can do it.

(Travelling and hiking on rice and vegetables seems to be very good for weight loss without hunger.)

How much water have you had? Eat something fatty and high in protein. Your body never enters fat burning mode - as you get used to fasting once per week this process will get easier, like anything really.

Have you tried gradually increasing the fasting window over time?