I basically follow the protocol all the time, although I follow it selectively.

FODMAPs = Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols.

The M part I follow pretty closely, insofar as I basically never eat fructose, because I never eat fruit. When I do, it's pretty much only fruit from the good list -- that is, fruit with higher glucose than fructose, like bananas or berries. When I do eat something from the bad list I tend to have some digestive unpleasantness. (The "M" stands for monosaccharides; of the three main hexoses, fructose, glucose, and galactose, it's only fructose that gives us trouble. Free glucose is no problem, and free galactose -- I actually don't think that's ever found in food, although I don't know that for sure. Probably it is rarely.)

The O part -- oligosaccharides, basically chains of fructose or galactose molecules of different shapes and sizes (chains of glucose (i.e., starch) usually don't give anyone trouble) -- is not that much of a problem for me. Well, things like asparagus and brussels sprouts sometimes do, but onions never do, and as far as legumes go, well, I seem to have a superhuman ability for effortless digestion of beans. I really don't understand it. (This paper, which I think is the best introduction to the principles of FODMAPS, says: "The mammalian small intestine does not contain hydrolases that can split the fructose-fructose and galactose-galactose bonds. Thus, fructans and galactans are almost entirely malabsorbed in all people." Whoops, guess they forgot me. I really think that some special bacterial population lodged in my gut back in my vegetarian days and is still chugging away, somehow fully consuming those galactans before the evil bacteria can get a hold of them and mess everything up. I can eat beans without ill effect even after many months of absence.)

The D part: well, in this context the relevant disaccharide is lactose (glucose + galactose). I have no trouble digesting it (NW European ancestry, lots of lactase floating around in my body still), but I never eat it anyway, since I mostly avoid dairy because of suspicions about casein. Anyhow, lactose seems to be different from the other things that fall under the FODMAPS umbrella, because you either have the lactase or you don't.

The P part I know a little less about. Most of those polyols are in weird stuff that paleos aren't going to be eating anyway: Maltitol, Mannitol, Sorbitol, Xylitol ... yikes! But back in the heat of my elimination diet I tried out some mushrooms and got bad results. I thought, mushrooms, what the heck? But it turns out they're filled with nature's polyols. Who would have guessed. (PS, I was surprised by Live Bigger's mushroom inclusion ... I guess these things are individual as always.)

And if you're wondering where the F and the A are, well, I don't eat "fermentable" and I don't eat "and." Does anyone?

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The qualification I would add to all of this is: if you eat these foods with other food then you're much more likely to be OK. And especially if you have small amounts of them with other food.

Now it may be that there is great benefit to be had from completely eliminating the kinds of things that bacteria can rapidly ferment. The goal would then be to rid the digestive tract of these bacteria and then at some future point be able to eat FODMAPs again to the heart's desire.

But I'm much more inclined to think that these foods (again, lactose is a different story) are just not foods we were intended to eat in large amounts. There is research to back this up, e.g., papers like this one: "Fructose intake at current levels in the United States may cause gastrointestinal distress in normal adults." The obvious response to such research is the response a lot of us Paleohackers have, and should have, to mainstream nutrition research: it's all performed on SAD dieters, so it really can't tell us that much. I think better support for my view comes from looking at the physiology: we just don't have as great a mechanism in our small intestine for the uptake of fructose as we do for glucose. Here's a quick summary, from that first paper I linked:

Fructose is normally absorbed in the small intestine via two routes: a low capacity facilitated diffusion via the GLUT5 transporter and a glucose- activated more rapid diffusion via insertion of GLUT2 into the apical membrane (24). Thus, fructose is well absorbed in the presence of equimolar glucose in the proximal small intestine (25), whereas free fructose is slowly absorbed and such absorption occurs right along the length of the small intestine.

So we just don't have the hardware to digest a whole lot of fructose at a quick rate. (Incidentally, this also explains the good and bad lists for fruit: if there's more glucose than fructose (e.g., bananas, berries), then there's less free fructose and less work for GLUT5.) Similarly, we just don't have the enzymes that break up fructose-fructose and galactose-galactose bonds. On the other hand, we seem to be well designed for the consumption of starch. From what I can tell, very few of us are lacking in amylase, the enzyme that breaks down amylose (and amylopectin).

Alternately, we can see this in degrees. Maybe you'll never completely get rid of the bacteria that are rapidly fermenting that fructose and those fructans. But you can limit them, and that might do a lot of good. This is all a murky area, and seems to be so for the researchers pursuing this as well.

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One more thing. If you are experimenting with a FODMAPs approach, you might profit from eliminating entire groups, rather than single foods. Because a lot of those single foods have certain properties in common: that's why they can be grouped together as they are. I guess this was implicit in my categorization above, but I thought it couldn't hurt to make it more explicit. Try thinking of the "fructans" as a category, and the "bad fruit" as a category, and so on. This will probably save you some time, or at least will help you organize your experience.

I did a very strict FODMAPs elimination from 05/10-09/10. I was incredibly frustrated by the lack of information available, and ended up combining a number of resources to create my meal plan- I was only eating unprocessed meat and fish, olive oil, spinach, mushrooms, green peppers, pumpkin seeds, pistachios, and stevia. No probiotics or other supplements.

Pros: My belly bloat and constipation ceased almost immediately! I felt more free in my belly than I can remember.

Cons: I lost too much weight and became very frail- I broke a rib while dancing, which I don't think would have happened were I stronger.

After those 4 strict months, I started experimenting with adding foods back in. I found that small amounts of pumpkin, broccoli, and colored peppers were okay. Small amounts being key.

Then I experimented with cultured dairy and probiotics, which brought serious bloating along with it, but I assumed this was the War of the Bacterias and allowed it to happen without freaking out.

Since then, I've freed up my diet quite a bit- my bloat is back off and on, but now I know what the cause is and can make informed decisions. I no longer deal with constipation, though, and I think this is due to letting my intestines have a solid time to heal.