I agree personal responsibility plays a huge part, people must want to make a change and exercise will power and self control. But don't you think people are set up to fail these days? Cheap, processed convenience food is so prevalent, look at a reasonably typical day if a person has a pub meal in the evening:
Breakfast: Toast with marmalade - If thick marmalade that'll be 600 calories without filling you up
Lunch: Shop bought meal deal with tons of mayo and barely any cheap processed meat, 600 calories, crisps 200 calories, bottle of so say healthy smoothie, 200 calories.
Afternoon coffee: Starbucks Java Chip Frappuccino 470 calories, just 1 cookie 360 calories
Dinner - Lasagna served with chips (!!!) 1500 calories
This person has taken in double the amount of calories that is recommended for a woman without really ever feeling like they're going overboard, and probably feeling hungry all day. There is a huge amount of carbs in all 3 meals and very little protein until the evening meal.