I'm afraid I'm not a medical expert Nonnie so can't give you an explanation , you just asked 'were there any' , and apparently there are.
I think it's too simplistic by a long shot to say people are obese because they over eat. Yes that is the end result but people over eat or in some cases just eat badly for many other reasons. They become overweight, it's less easy for them to be mobile, their mobility is compromised so they put on weight. It's a vicious circle .
I have observed over time that obesity is a topic that has no middle ground. Very often people who have never been over weight in their lives struggle to understand how people can 'let themselves' become overweight. There is often precious little compassion for the overweight 'because they did it to themselves' . Nothing is ever as simple as it seems.
I would suggest we should all walk a mile in another's shoes before we 'preach' whether that be about obesity, alcoholism, smoking etc.
You're right River you pay for one seat and should purchase a second if needed. Luckily for me , I don't have that need . One thing worth mentioning perhaps is airline seats and legroom have gotten progressively smaller in the last 30 years , just in time for us to get bigger. Once upon a time flying economy was fine , now the recline of the seat in front means the person behind is within a few inches of the back of the seat in front. 15 years ago the seat pitch for a Delta flight was 36 inches . Now it's a maximum of 30 inches and even less in some cases.
The width has also decreased it now averages out at 18 inches in economy.
Some planes now go as far as to have a 28 inch seat pitch and what they euphemistically term " a pre reclined angle" so they don't even move.
Even slender people are going to start feeling the crunch at this rate. I have attached an image from a report on airline seating, and it shows only size 14 and under actually fit in an average size economy seat.
Food for thought eh ? ( low cal of course !!) 
Are you in your forever house?
Retiring and living frugally in money from downsizing after years of stress




