I was a child in the Sixties. We did have quite a high carb diet then and the only convenience food we had tinned soup, tinned meat pies, ready meals were not available. But I remember the food as being very tasty. Suet puddings, rice pudding, shepherds pie, yorkie pudding, dumplings, rissoles, roast beef. And lots of veg too - soup, lentils, pease pudding, cheese and onion pie. Haddock and mash with egg.
I think in those days we used up a lot of the calories we ate to keep warm because the houses we lived in were so bloody freezing cold! One coal fire heated the whole house. I can remember ice on the inside of the windows in winter and going to bed wearing bed socks and knitted woollen bed jackets. How my mum ever washed and dried any clothes or nappies in the winter months before the advent of a self service laundry I don't know. We wheeled it there and back in my sister's pram.
Sweets were a treat on Fridays. Maybe a small cake like a doughnut or Florentine from the baker on a Saturday lunchtime followed by a traumatising episode of Doctor Who in the evening. Also vegetables were seasonal. You could not get veg like tomatoes, cucumbers, lettuce or oranges year-round.
The advent of refrigerators, freezers, a profit-hungry food industry selling mostly crap food often to consumers who are uninformed or disinterested about nutrition; then using TV advertising and marketing campaigns to promote their products such as 'health-giving' breakfast cereals for kids, has resulted in a deterioration of food choice. Children see these ads all the time BTW.
Just look at the incidence of newly diagnosed diabetics in the UK including children. Sorry rant over there!
OP, YANBU, people were definitely thinner.