I think it's both our own fault and not our own fault. (I haven't read all 14 pages btw, sorry). Let's not get too fixated on the 1940s; we are surely fatter than ever before in history.
Capitalism fills the world with horrid sugary fatty food. It's cheap to make and guaranteed to sell. Go to a poor area of London and all the food outlets are fried chicken shops. Go into a newsagent and you'll be greeted with an entire wall of sugar (in a newsagent, for goodness's sake! It's supposed to sell stuff you read.) I recently went into a WH Smith needing some lunch and there was literally nothing to buy to eat there that wasn't arguably poisonous, apart from some brown bananas and manky apples.
People have less will-power than before. No-one is ever bored because they have their phone to read facebook / play candy crush / text friends etc etc. Shorter attention spans match to high availability of quick-cook food (because we're all so much busier than our forebears - thanks, capitalism) and that creates an expectation of going from hungry to full in a short period of time. Thus we eat more crap.
Almost nobody is a stay-at-home parent, preparing a proper meal from fresh ingredients for the family at the end of the day. Fly in from work, chuck the chicken nuggets and chips in the oven, phew done. Vegetables? Oh yes I think we've got some frozen sweet-corn. It's so easy to do. I've done it.
Fewer of us are manual labourers than at any point in the past.
People have forgotten the difference between being properly hungry and just craving sugar. I think in terms of 'mouth-boredom'.
Snacking is socially normal. Compare to France where people are generally not over-weight: they only eat at meal-times. (The difference between Paris and London is visible and terrifying in this respect.) 'Pourqoui tu manges maintenant?' 'Pourqoui tu manges ca?' 'Pourqoui tu manges ca maintenant?' They arrive at meal-times properly and rightly starving hungry (which is why they hold their meals in such reverence)! Compare to the UK; the high-street I just walked down had people munching on sausage rolls and crisps at 10:30 in the morning; coffee shops have big adverts for pumpkin-spiced lattes full of sugar syrup and full-fat dairy. The French generally drink their coffee black, of course.
Being overweight is just normal in the UK now. Again in France, Mothers say 'tu devrais manger de la soupe pendant quelques jours' when they think their children have put on a few pounds. People's weight is closely monitored as part of looking after each other. Here we make our friends and loved ones an excuse to eat badly ('Oh you're no worse than me darling! The other day I stuffed my face with [blah]').
I don't know what the solution is. I was interested by the Scottish Minimum Unit Price approach to alcohol. Maybe we need something similar for sugar? I don't think the gym-bunny culture (as observed in the offices of a few PPs) is the solution. It seems to be a fairly new thing among the relatively well-off (or at least it's got much more prominent than it used to be); I'm guessing it comes to us from Hollywood? It's only really penetrated the metropolitan elite though, not the population at large. My worry about using exercise-addiction as a means of maintaining a healthy weight is that it's not realistically sustainable for everybody into middle- and old-age (not to mention new-parent-age! I was smashing the mars-bars just to stay awake when DC1 had just been born and it took me four years to get rid of the weight!) They're all really good-looking though, for the time being!