Another 40-something here.
Agree with most of what's been said here.
"mothers did not ask their children what they wanted to eat etc." My mum cracks up at kids being given so much choice on meals now. We'd one choice - eat it or starve! And yes mostly beige, chops, mince, faggots, offal... Yum
(not envy) I'm veggie now 
But also not just portion sizes but product sizes were smaller too 'small' packs of crisps can be as much as 45g now where back in the 70's they were 10-15g the ones we had our of multi packs for packed lunches. supersized chocolate bars etc too.
Yes white bread but it was thinner sliced and smaller area than now too (my mums still got her 70's bread bin
and 'normal' sized loaves of now are far too big for it so she gets 'danish' loaves that fit).
Sweets on Saturday only paid with using our ltd pocket money. Pudding on Sunday after Sunday dinner.
No tv remote, only one tv, few programmes worth watching.
Walked to school (couple miles at least- rural) one car and dad needed that to get to work which was a fair distance away. He had a manual job. Mum worked part time (usually quite physical jobs too plus walked to work) plus did all the housework (no dishwasher, no tumble dryer, no freezer till I was in my teens), no central heating till after I left home.
Also yes playing out and even as teens cycling/walking to friends houses to 'hang out' and when there dancing and singing to pop music. Summers going to the swimming baths was the thing to do, not watching screens or playing computer games.
But yes thinner =/= healthier. Parents smoked heavily, dads an alcoholic, 2 grandparents also smoked heavily and 1 who didn't but lived with one of the heavy smokers died young of a condition likely caused by the passive smoking. My siblings and I have all lost friends/schoolmates in car accidents (no seat belts/more drink driving then).
Definitely remember dieting/exercise being around then. Nimble bread etc I've an aunt who's always been slim but also always been on a diet of some kind since the 70's.
But each generation it's different health problems. My grandparents who were extremely poor lost friends and siblings to malnutrition and poverty borne conditions, lack of vaccinations and decent hygiene.