I agree with LaurieFairyCake. Lifestyles in the UK tend to be very time- pressured because both parents are often working in jobs with long hours. This translates into less time to shop and prepare food, less opportunities to eat together, less ability to walk children to school etc
We are also very out of touch with the food process compared to say the french who buy at local markets - we buy anonymous processed food from anonymous supermarkets.
Then there is the problem of poor quality school meals
Also the dire low level of exercise and playtime in the school day and the number of kids who don't walk to school for a combination of complex reasons.
Not to mention that huge numbers of overweight people have emotional problems that are blocking their ability to lose weight, because whilst you ignore the emotional root of the problems you can never address the real cause and are pretty much doomed to failing in attempts to treat the symptoms only.
And finally, surprise surprise, it's really just not as simple as eat lessand exercise more. There are many genetic factors involved that we are only scratching the surface of understanding.
So the problems are genetic/behavioural/educational/emotional/driven by economics and often combinations of these factors.
What makes me so very sad is how its still widely accepted as OK to deride and mock the overweight.