Gained 9 pounds in one week on unlimited vegetables and shirataki noodles.

Open up your food diary. As an "experiment" you need more than a week, and food intake has to be precise, if not, there's not much value to the experience.

On your noodle and veg diet were you doing a poo every day?

Was the ice cream diet the week straight after?

IBS is a very complicated thing. I hope you are getting support from your medical team. Thinking constipation I expect you are keeping hydrated, dehydration adds to the issue. High fibre can be counter productive too. The causes can be so different for each and every sufferer. Have you heard of salicylate Intolerance? Much of the work into this was done at an Australian Hospital, Royal Prince Alberts (or at least those initials). Some have difficulty in digesting salicylate, its a substance which plants use to protect themselves from moulds and mildews, there are several on-line sites which provide information. The Finegold diet did not go far enough for myself in sals elimination. There is also Histamine intolerance, histamine is produced on different foods as they age some of us react at earlier stages than the majority. One can be intolerant of other things like oxalates/sulphates and more. Some find the FODMAPS diet helpful. It groups foods by the sugars they break into or the ways they are digested how they effect the body as they are absorbed after digestion.

Many people will scoff but using digestive microbes can help improve one's digestive biome. If we lack the quantity and diversity of microbes our foods will not be digested efficiently. Medications particularly antibiotics though others have this as a side effect , excess sugar in the diet and inheritance can all effect our personal biome. I would suggest looking for something which does not increase histamine, a few digestive microbes do increase histamine levels and our reactions.

Many with IBS have allergies or intolerances, where as allergies have virtually instant reactions intolerances can take longer to show up, they can be really insidious. the common ones are gluten, which is in most grains some grains are free of it. I think we can exclude casein and lactose but dairy is often a trigger, those who say they are lactose intolerant are probably more reactive to casein which is the dominant problem. Having allergy and intolerance testing can help avoid eliminating things for them to do little or nothing to improve your condition.

For those with intolerances they may find digestive enzymes useful, they come in single or multiple products to help digest fats, proteins, starches etc. Some are made to work to digest salicylate. There can be many different reasons for enzyme problems, they can be nutritional or microbial. For instance where the body lacks adequate vit c and vit B 5 or 6, the body is less able to deal with histamine.

I've probably given you far too much to think about. Please do your own reading and follow your own symptoms to achieve relief for yourself this way rather than throwing yourself into eating only one food for a week which can make the whole problem much worse.

As a side thought, constipation can be caused by endocrine disruption but this is a difficult problem to get addressed properly. All the very best. I hope you achieve comfort.

If you have a bowel disorder it would be best to talk to your specialist about finding the right way of eating for your needs

First, the body doesn't react immediately to everything you do, so a one week experiment isn't telling you very much. You could easily be seeing changes in your body this week that were caused by a change you made 10 days ago. When you make drastic changes every week, you are just challenging your body and probably causing all sorts of weird fluctuations in digestive transit time and water weight, not to mention confusing the heck out of your endocrine system.

Second, if you have medical digestive issues, switching from one extreme dietary change to another weekly without the previous knowledge of your doctor is a recipe for disaster.

I agree with pretty much all of the above, but want to add this: I read some research that said digestive transit could take up to 50+ hours. Nutrients continue to be absorbed during a good bit of that, and it takes some time for them to be processed biochemically into useful forms. Therefore, even ignoring the effects of constipation, you're well into your experimental week before you start seeing any net fat effect from the experiment, and - when you do the experiments back to back - well into the second experiment while still experiencing effects from the first one.

Poor experimental design, so completely meaningless. Plus meaningless for the reasons everyone else said.

Suggestion: Why not consult with a registered dietician to follow a sensibly balanced diet (from a nutritional and caloric standpoint), and eliminate foods in a properly structured way to see what sensitivities you may actually have?

(I've been diagnosed with IBS-C myself in the past, but rarely experience symptoms nowadays when eating a sensible, balanced diet with enough fiber, enough fat, adequate hydration (from water and foods), and regular exercise (especially exercise that involves moving the midsection). You may be less lucky than I, but I'm pretty sure your current approach is going to be a poor way to find a solution.)