Starch can be used by any potential nasties (i.e. bacteria) that might be hanging out in your intestines for fuel . In contrast, most mono and di-saccharides (such as those found in fruit) are metabolized before any invading bacterial colonies can feast.

This is from the info page on the SCD (precursor to GAPS):

"The allowed carbohydrates are monosaccharides and have a single molecule structure that allow them to be easily absorbed by the intestine wall. Complex carbohydrates which are disaccharides (double molecules) and polysaccharides (chain molecules) are not allowed. Complex carbohydrates that are not easily digested feed harmful bacteria in our intestines causing them to overgrow producing by products and inflaming the intestine wall. The diet works by starving out these bacteria and restoring the balance of bacteria in our gut." (from http://www.breakingtheviciouscycle.info/beginners_guide/beginners.htm)

Speaking from personal experience, starches can be far harder to digest than fruit.

I can digest any fruit without a problem. White potatoes and white rice make me feel like I've eaten a bag of concrete, and give me acid reflux to boot. Sweet potatoes are somewhat better, but I still don't want to eat them in any quantity. Starches also make me bloat like mad.. I will never have a bigger gut in my life than when I am eating starches. (For the record, no amount of probiotics, bone broth, upping my carbs with other things before adding starches, or any of the other recommendations did a thing to make this any better.)

Apples, pears, bananas, kiwis, oranges... you name it, my body has no issues with these at all. No concrete. No bloating. No swelling. Actually, I think they have improved my digestion by quite a significant margin.

I have been toying with the idea of sprouting some rice and seeing if that's any better, but I'm not holding my breath at this point.

Wait a minute. Isn't starch just a chain of glucose? Fruits contains starch. And I thought that bananas are among the favored fruits because they are relatively higher in starch and lower in fructose than other fruits. Following shows about 25% of carbohydrate in banana is starch:

http://ndb.nal.usda.gov/ndb/foods/show/2260?fg=&man=&lfacet=&count=&max=&sort=&qlookup=&offset=&format=Full&new=

Starches are made of long chains of glucose and therefore take longer to digest compared to monosaccharides (fructose and glucose). The GAPS diet eliminates starches because if you have digestive issues, you are likely not digesting starches well and these starches are then more likely to stay in your gut and be fermented in your intestines, contribute to SIBO or other digestive disorders.

Monosaccharides, like these found in fruits and squashes, are usually better tolerated because their carbohydrates are digested more quickly and you are more likely to absorb them before they reach the regions of your gut where high amounts of bacteria live and can start fermenting these sugars. However, some people with SIBO (small intestinal bacterial overgrowth) can't even tolerate fruits and squashes. I agree that even fruits, non-starchy vegetables and squashes contain small amounts of starches, but not as much as grains or tubers, which is fine for SOME people. Individualization is key with the GAPS diet.

The GAPS diet is not a high-fructose diet by any means. Some people don't eat any fruits and honey. Other can. But in any case, the GAPS diet is a relatively low-carb diet compared to the standard American diet.

I'm right now on GAP intro protocol, stage 6.

Fruit doesn't come right away but they do start you right off with carrots, squash and pumkin, a good alternative starch.

I get omitting starches like rice (that bothers my system), but for me, potatoes arent a problem.

Potatoes and rices are omitted for the purpose of starving yeast over growths, which removal of these items helps to starve.

I was recently traveling and had a problem with the food they gave me, grilled chicken soaking in oils which I couldnt look at let alone eat, I opted for a potatoe 2 nights in a row and I'm perfectly fine and felt no ill effects (but they were expected).

I'm back on protocol again but was happily surprized to see that it didnt have any outward or obvious effect on me, but back to legal foods only!!

SCD allows fructose, because it is a monosaccharide. However, many people have problems digesting even fructose and it cannot be part of THEIR diet, at least until they have healed sufficiently. Fructose feeds Candida, so if Candida is part of your problem you should avoid it.