I'm overweight at the moment - I've recently come out of the obese bracket, thank goodness. I was slim throughout my childhood but as an adult my BMI has fluctuated between 19 and 35. I first gained weight when I started work for the first time, in the mid-1990s and since then it has gone up and down several times.
If I look at the difference between the food I ate as a child and as an adult, what sticks out is processed food. When I was a child we ate very little processed food - not a conscious health decision, it was just the way my mum was used to cooking - meat and two veg type meals, stews, casseroles, all done from scratch. Takeaways two or three times a year at most, usually on holidays. Eating in a restaurant similar. No 'fast food' e.g. Macdonalds - not on health grounds but because it was a 'waste of money'.
As a young adult working full time, I relied heavily on ready meals and so on, and that's when my weight first started to go up, and over the last 25 years it's been in a cycle of going up until I can't bear it, and go on a diet (calorie-counting) to bring it down, but then it very slowly creeps up again ...
It's only recently that I have started to look at what I eat rather than how much I eat - what's actually in that Tesco lasagne I so readily bung in the oven when I get home from work, for instance. And when you look at the ingredients on packaged meals, it's quite shocking - there's so much there that really isn't 'food' - 'modified' this, that and the other, stabilisers, regulators, flavourings. Many hidden sugars, particularly in things labelled 'low fat' which many people probably believe are 'healthier' than the full fat version. I don't think our bodies are designed to process all this stuff.
I have now cut out processed food and cooking everything from scratch. I'm using unmodified (i.e. full fat) natural ingredients, such as butter and olive oil rather than sunflower oil and margarine. My weight is going down again and I'm hoping that if I continue avoiding processed foods, or, at least only having them on rare occasions, I can reach and maintain a healthy weight.
In summary, I blame the obesity crisis on our reliance on processed food.