This is a valid point. On a doctor monitored weight program I found out: At my height (5 feet nothing) and metabolism I have to work out 2 hours per day 7 days a week and consume 1200 or less to maintain being 40 pounds over weight.
Unless you have some other health issues in play this is not true. Trust me if you're just overweight because of overeating and lack of exercise if you follow what you suggest above you will lose weight rapidly. You won't be able to work out 2 hours a day if you're 40 lbs overweight but you can target that to build up to. And 1200 calories a day is very few, especially if youre working out with vigor.
This is one of the prominent excuses people use, along with "working out will make me eat more so I don't do it" If you have a health issue that makes your metabolism that slow that is a different story but for most people its just bad choices of what they're eating or the lack of any exercise.
The problem I see is people are just too darn sedentary. Technology has made it so easy to be. I bet if you asked 10 people if they worked out vigorously regularly let's say 4 times a week, it would be 3 out of 10. 3 more might get moderate activity and the other 4 would get none. If you don't exercise regularly you will not be healthy, unless you eat and drink like a teetotaller. I'm going to try to research that and get back with stats.
I work out almost every day in one way or another. I'm at the gym lifting weights and running or biking at least 4-5 times a week and then doing vigorous yard work the other days, and actively coach all my son's sports teams.
Now I am still 15lbs over weight even with all that good exercise because I still like to eat rich foods sometimes and indulge in a cocktail or two. I can tell you for sure the way I eat and drink if I didn't exercise so much I'd be one of those in need of 2 airline seats but I have a nice balance I think.
I feel good about myself except for my bald head because although I carry the extra weight my doctors just recently confirmed I am a very healthy 47 yr old, and in fact said I was 10 years younger than my peers health wise, even being a little chubby.
So it comes down to personal effort to keep yourself in reasonable shape. Even the people that now have health issues that make them obese, many got that way because of bad habits when they were young and not something genetic.
This may sound like a simple way to solve it but to be fair anyone who can't fit into a seat and has a legitmate medical reason why they are obese should be able to get a doctor's note to justify, and get a free seat from the airline, otherwise they should buy two seats.