I hadn't realised how difficult it was or how little PE was done in the Schools. Looking back I used to play loads of Football and cycled everywhere which as I explained to my Daughter gave me a great base fitness level despite gaining lbs, and then losing them once I got back on my bike.
The fact of being overweight is that it is not genetic, or at least it is very rare. There are people who are able to consume calories without gaining too much weight but these are not the norm. If an overweight person who says it is genetic and claims they do not eat much was put in to a very controlled environment where food was issued and calorie controlled and a varied excercise program they would lose weight. Often it is a mental problem driving it.
I know that if there are Chocolate biscuits in the house that I will consume some and if I restrict myself I might be able to only have one with each hot drink. 5 Teas and just five biscuits is 430 calories and an hour on my bike to burn that off, the 430 calories are not very good either.
When you get someone to do a food diary, and IF they are honest it is often very easy to spot 500+ empty hidden calories a day, or put it another way 15000 per month or 6 days extra food every month over and above the 2500 suggested for an adult.