This is a great thread.
In case this adds to the conversation:
I did some international travel Summer 2014 and didn't have any trouble bringing about 10 baggies of veggies and leafy greans in my carry-on. I also took dry packets - bars, chips, and powders in the carry-on, and that was fine. I have a friend who took Beef Stroganoff and because it was liquid they took that, FYI.
I likely went through 4 to 5 different countries' security checkpoints, dogs sniffing/passports/all luggage checked/pat downs/many questions, etc. (not because of IP, just the procedure for everyone in some places).
I also packed about 2 weeks worth of "dry" items and also 8 pre-made puddings in my checked bags, and that was also fine.
Like others have suggested, I mixed things in water bottles (I would drink it and bring the empty one through security between different country's checkpoints) and also sometimes buy a black coffee and then use the cup to mix up some cereal, etc.
Everywhere I went I was able to get green salad (some countries you need to be more careful about raw veggies because the bacteria might effect you poorly, but I was OK - in Africa I mostly stuck to cooked veg though). I usually just found a grocery store when I would arrive in a country and pick up more veg, wash it and use the ziplock bags I had to "replenish".
If I couldn't find 8oz. protein for the day, I just ate an extra bar. I didn't worry during that time as much about restricted, if I needed to do 2 bars rather than 1 I was fine with that, and if I did a lot of walking I added a packet for the day.
Overall it all worked great, restaurants were very accomodating, I would just learn in the given language to say some version of "I have medical problems, no sugar no fat please". I was able to stay 100% IP Compliant and came back with 10 lbs lost.
p.s. I did ask ahead of time for the "low fat low calorie" gluten free meals on the planes, thinking maybe it would get me some extra veg or edible protein, but it was pretty useless. I might have gotten a hard boiled egg or a few ounces of chicken, maybe a few pieces of steamed broccoli from it overall, but mostly it was still full of sugar and fat and dressing and carrots

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