Not all people who are overweight are gluttons various medical conditions can cause the body to increase fat.I for one had a problem of weight gain through no apparent reason I ate one meal a day and walked 6 kilometres every day with no decline.After an ultrasound for an unrelated symptom they discovered a growth on my adrenal gland which made the body produce to much cortisol,a friend in small doses but the body's enemy in large amount.solution they removed the gland and in a matter of a few months I lost 10 kilos.
In my observation they must be among the most unhealthy air passengers i have encountered by the number requiring wheel chairs to board flights, but strangely on reaching their destination are able to disembark quite briskly.