No problem

I just got back from a trip from San Diego to London on American Airlines in coach. I'm 6 feet tall and weigh 330. I think I am right on the edge of being able to do this in anything resembling comfort. With the seat belt all the way out, I can just buckle it (I own an extender, some of the seats have shorter belts!) My biggest problem is not the width, but the leg room - on the way back my knees were hitting all the way - in really uncomfortable places. On the way out however, I got to sit in an aisle seat right behind the bulkhead where the big screen is (in a 777) This was wonderful! I could stretch my legs all the way out! Couldn't even do that in the one time I got a first class seat. There are about 20 coach seats in specific places that allow for more space, AA charges more for these seats, but it is generally worth it! I always try to book an aisle seat on the side where there is only two seats - that way I am only blocking one person and I can lean out into the aisle. I know I wouldn't want to sit next to someone my size (unless they were female and friendly!) because I do take up more than my fair share of the available space.

I already pay extra for those more "spacious" seats and I almost always have to pay more for my luggage. Bigger clothes are heavier! I own a big Samsonite hardside suitcase. Fully packed for this trip it weighed in at 67 lbs. $50 charge right there. I didn't even bring my heavy jacket on this trip, I could have easily gone over 75 lbs. I was also lugging a carry on and a backpack.

So, I think the "Total Weight" including luggage idea would work as long as you got extra space to go with the extra expense!

Some of it you're just going to have to learn by trial and error. Some foods give me problems if I eat them in large quantities or not. I've had intestinal problems in the past too, but I also had them when I was actively dieting at one point. Things are actually slightly better now that I stuff on occasion, but I also try to get enough fiber. It might sound slightly strange, but stuffing a balanced diet makes things easier to handle "on the other end". For me it's the volume, not so much what I stuff with that makes things interesting.

I tend to do better with a variety of items - trying to stuff all one thing tends to make me feel more queasy and I start to develop some aversions. The only time I really puked after after stuffing was when I downed a whole extra large pepperoni and sausage pizza - it was really greasy and I just couldn't keep it down. Too much cheese and the sausage was really spicy.

All-you-can eat buffets are a really good option - lots of different foods to peak your appetite and you don't get bogged down on one item. Make sure to drink enough liquids and take lots of small bites - helps to pack in those last little nooks and crannies!