I don't always fast intermittently, but when I do, I skip breakfast.

Yes and no. Yes, if you skip breakfast and have lunch and dinner, and no snacks between waking and lunch, you are doing IF. No in the sense that you can do IF by skipping dinner instead.

No, it doesn't matter, the effect is the same. Dr. Jack Kruse recommends protein for breakfast if you are doing a leptin reset.

Also, it's probably not a good idea to do IF if you're just starting out on a Paleo diet, or are trying to kick the carb habit. But once you're over those two hurdles, by all means IF away.

Keep in mind that the Leangains protocol, and also what Art De Vany recommends is to work out fasted. Leangains suggests taking 10g of BCAA fairly soon after waking and again before working out, and once more an hour later for a total of 30g. This is to send a signal for muscle growth.

De Vany recommends working out fasted so that we kick in autophagy and/or ketosis and do an insulin reset as well. He also recommends not eating for at least an hour after the workout. There are several answers around here that relate to that and the reasons for it.

So this is slightly different than just skipping breakfast. The key there is that you get more authphagy if you're active and work out. The BCAA is optional of course - if your goal isn't to build muscle, skip it.

The conventional wisdom of course states that you have to eat every few hours and that you should do a pre-workout protein shake and a post workout protein shake. Of course, this "wisdom" is designed to make money for the protein shake industry, and isn't designed to make you healthy. :)

The only thing to keep in mind is that overdoing fasts is going to lead to loads of cortisol release. Cortisol is released when glucose levels get too low as a signal to free up some fat and convert them into ketones and to create some glucose from protein stores - i.e. muscles. Too much cortisol releases can lead to all sorts of problems, so don't do chronic fasting either.

If you over do it, you'll notice your heart racing and sense of anxiety for no reason at all (i.e. typical stress response, but without a clear cause.) If you notice this, eat immediately.

Doing IF a few times a week, especially when working out is perfectly fine. Doing it every day is not.

EDIT/Addendum: since there were a few questions below, rather than answer in more comments, I'll edit the post and move the answers here:

Links to papers on Cortisol and Fasting: This is what I could find, there's probably better out there. I'd ping Jack Kruse, or look at his blog posts for references to theseas he's a Rock Star when it comes to hormones.

Fasting Alters Pulsatile and Rhythmic Cortisol Release in Normal Man

Effects of prolonged fasting on plasma cortisol and TH in postweaned northern elephant seal pups.

Effect of intermittent fasting and refeeding on insulin action in healthy men

Cortisol Is Negatively Associated with Insulin Sensitivity in Overweight Latino Youth - PubMed

Hepatic de novo lipogenesis in normoinsulinemic and hyperinsulinemic subjects consuming high-fat, low-carbohydrate and low-fat, high-carbohydrate isoenergetic diets

BCAAs when you're not working out: it's probably not going to be very effective. You need to damage muscle fibers to get the anabolic repair process to rebuild them. If there's no damage, there's no growth. But, as long as you take in enough protein (and/or carbs), you don't (immediately) go catabolic so there's no neoglucogenesis.

If you don't work out at all, your muscles will eventually atrophy to their level of normal use. Our bodies are adapted to save resources, so unused muscle, which is expensive will be catabolized.

It's especially critical to address this once you pass ~50, as sarcopenia sets in, and then decrepitude. I'm not near that age, but would want to bulk up way before nearing it, so that there's plenty of headroom for when the grim reaper starts to sharpen his scythe.

Can you do daily IF: You can do it every day as long as you don't trip your cortisol too much as it has some nasty effects long term. If your glucose goes too low, you get cortisol trying to get more glucose - that's the anxiety heart racing feeling. If you don't chronically trip this mechanism, it's fine, but likely you will if you don't have some carb/protein intake, or enough skeletal/liver glucose stores.

BCAAs when not fasting: I've had good results taking it even when not fasting, though I'm not sure that's a placebo or not. I suspect a lot of that is wasted since the same aminos are in meat, so taking BCAAs when not fasting is probably not going to have any extra effect over just eating meat.

However, it does seem to signal muscle building, so you'd have to eat a lot more meat to get the same level of those aminos, hence process a lot more calories. Since I'd like to lean out those last stubborn 10-15lbs, I opt for the BCAAs instead of extra protein via meat (which will have an insulogenic response.) Then again Dr. Eades recommends an all meat diet if you're trying to lean out, so it might not matter. Not sure.

In terms of cost, I find the 10g-30g of BCAA a day to be far cheaper than a bunch of extra grassfed bison steaks (which is something like $12-$15/lbs or so), or even CAFO meats. So I don't mind taking extra BCAAs and letting it go to waste. (Now BCAA Powder goes for something like $17 for an orange container, and lasts me about a month. They taste awful an don't dissolve in any liquid I've tried, so I just take two teaspoons and wash it down with water. But at least there's no artificial flavoring and sweeteners and other crap.)

What I do is this: I do a morning IF on days that I work out (and sometimes other days.) After the workout is done, I don't eat for about an hour. When I've had a particularly large workout (usually 1 day on the weekend), the next day I don't do IF though I usually take the BCAAs if I remember to, both because I want to rebuild those muscles. Two days after the heavy workout, I'm back to IFing.

Sometimes, one day a week, I do a much longer fast where I skip both lunch and dinner, this is usually Wednesdays and I rarely work out on those days, if I do, it's a light workout.

On the days that I do the large workouts, I split the workouts in two (lower + upper body.)

The 1st half of my workout is on an exercise bike. Crappy I know, but I set the resistance up to the maximum and do something like 20-30 minutes, so it's really resistance training. I don't take any BCAAs or creatine before this, except for the 10g of BCAAs on waking which is at least 30mins before the 1st workout. I also have coffee before this workout, so that the caffeine opens up the fat cells for easier loss.

Then I rest for 30-60mins, and have a small bit of carbs and rest another 30 mins at least. 15 mins before part 2, I take about a teaspoon of creatine and some BCAAs, in another coffee, then it's upper body work with dumbells. Stuff like rows, presses, clean + press or squats, curls, db raises*, shoulder exercises, etc.

I do multiple sets of each exercise with different weights, then move on to the next exercise. Got the idea from De Vany, though it's not quite what he does, and he wouldn't approve of the curls. (1-2 sets with a pair of 25lbs dumbells at high reps, then 2-3 sets at 40lbs at medium reps, 2-3 sets at 50lbs at lower reps. I want to get a set of 65lbs dumbbels and ditch the 25lbs ones, but nothing is locally available without special order, and the shipping costs the same as the dumb bells themselves.) So each exercise is a pyramid.

• I do two types of DB Raises, one to the front of the chest, and another like this, but on this 2nd one I rotate my wrists inwards on the lift and outwards on the drop, so it also works out the forearms.

About an hour or so after the workout, it's time for lunch, which does have some carbs, usually sweet potato, but more meat than carbs.

Without those bits of carbs in between the two halve and at lunch, I feel like death for the whole day, so for sure I know that I depleted my glucose on the 1st half. The creatine provides some ATP for the 2nd half.

This is probably not perfect, and I'm sure there's ways to improve it, but it seems to work nicely so far. I'd love to hear ideas for improvement, and a source of where to get cheap 65lbs dumbbels (or cheap shipping on the same) as that's the obvious improvement I need to make soon.

Well, there's many different types of IFing, skipping breakfast is one. Precision Nutrition has some useful info on three types here but there are others too, like an extended fast of 36hrs or more.

That said, my version of IF is essentially skipping breakfast too. And if I really want a calorie buffer (say for Xmas dinner), I'll either skip lunch too or just do essentially a protein "snack" for lunch.

I think skipping breakfast works well as long as it really works with your hunger (doing paleo means I'm not subject to mad hunger due to wild blood sugar swings). In the past, I'd skip breakfast because I'd eaten way too much late in the evening and by lunchtime I was ravenous, and I'd start the binge/fast cycle all over again.

So context matters too ;).

Yes, unless it's not.

There are different protocols for IF, but the one mainly used is the 16/8 protocol of never eating breakfasts. If you always ate three meals a day at 7, 12, and 6pm and then just didn't eat one day that is also IF. Rigid schedules such as 16/8 are good for people who like control, but your wife's schedule is natural and she doesn't have to think about it to still benefit.

Your wife surely is reaping the benefits of IF without even having to think about it. I suggest just not telling her what's going on behind the scene and rolling with it.

I don't eat breakfast, but I don't say that I IF though. I think a lot of folks just like to claim they IF because IFing is cool and trendy. Skipping breakfast makes it easy to be cool and trendy. I wouldn't call a fast a fast until you've gone 24 hours without food. I used to do an intentional "eat/stop/eat" fast once per week, Sunday dinner fasting until Monday dinner. Benefits weren't noticable after a couple months, especially since I generally do what most folks call 16/8 fasting everyday.

I did a pretty regimented "Fast 5" style IF stint in 2009 for several months. Then I tried (stupidly) the Eades 6 Week Cure and had to widen my window to accomodate all those shakes and such. FF a few months and I could NOT get back to my IF pattern that had become second nature to me. FF a few months more, and I realized that I informally IF 3-4 days per week. I've never been much of a breakfast eater since I became of age to decide.

I'd say, as long as your wife isn't snacking until midnight, she qualifies.

BTW, if anyone reads "historical" literature -- I'm talking woman-to-woman type advice and such -- they will find that IF is the norm for "women of a certain age". Two meals instead of three.

I eat dinner at about 6:00 p.m. and breakfast at 10 a.m. and small snack for lunch at 2 p.m. So, although I'm eating three meals a day, I figure I'm doing an IF every day because I go 16 hours without eating. It works well for me.

Turn the two terms around:

And then remove the word "just," because very seldom is any X "just" Y, in the sense of "nothing but."

Perform those two operations, and my answer to your well put query is:

Yeppers.