Overweight and obesity are defined as abnormal or excessive fat accumulation that presents a risk to health. In adults, a body mass index (BMI) over 25 is considered overweight, and over 30 is obese.
an easier solution is to set up a section of seats in economy class wirh shoulder height partitions between them. The fatso's won't buy those seats. Another plus would be to keep people from laying across the seats.
https://www.who.int/westernpacific/health-topics/obesity?source=patrick.net
BMI calculator:
https://www.nhlbi.nih.gov/health/educational/lose_wt/BMI/bmicalc.htm?source=patrick.net
https://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/english_bmi_calculator/bmi_calculator.html?source=patrick.net