There are some pretty cut and clear cases though:
Cheap junk food that are high in sugar and salt is not one of them.
Choosing to chug 40 cigs a day is.
There could be a
consensus found on many things, but even with the two choices you have given, there are other views; a child being given or allowed over indulgence in junk food by a parent or adult, this can be considered a 'no other choice', for the adult, if that adult does not have enough income to feed their children more healthily.
Admittedly, smoking' 40 cigs a day is a more difficult 'lifestyle' indulgence to deny , but I know smokers who maintain if they didn't smoke, their nerves would be shot to pieces and they would balloon up in weight and become obese? They rationalise it (at least to themselves)in these terms.
Certainly over the years definitions of 'lifestyle choices' and 'no other choice' definitions have become blurred, if you go back 40/50 years ago (at my age this is possible!) a 'one parent family' was only recognised in social terms, and in many areas of being in receipt of public benefits, if the 'one parent' was either a 'widow or widower'. And any form of single-parenthood outside of these parameters was non-recognisable and 'lifestyle choice had not been invented (or even thought of in those terms).
This has all changed of course, as divorce became easier, second third and so on marriages, became more prevalent, people cohabiting or living together (once called
living over the brush) mostly those involving children, became more prevalent 'lifestyle choices' and accepted as such.
Over this time the biggest single factor that produce a lot of public outcry, at times bordering on anger, was when increasingly the family 'bread-winner' (not always males, but predominantly so) started to disappear 'off the radar,' leaving the state to bear the full brunt of looking after the children (and partner) left behind.
Of course such situations are mitigated when domestic violence/abuse is involved, then it was no longer a 'lifestyle choice', but 'a no other choice' for those on the receiving end, which was usually (but not exclusively) females.
In Maggie Thatcher's time the government did try to introduce legislation to track down the absconding/defaulting persons (again usually males) and extract from them contributions to support their abandoned families, but it never really worked out, tracking down people became difficult, costs associated didn't meet the expectations and in many cases by the time the absconders were tracked down, they had started in true 'lifestyle choice' again in other relationships, also involving children... so it became a 'chasing your tail' exercise.
However when times are hard and needs must, as it appears now, then I suspect Starmer and Reeves will once again have to open 'the can of worms' that is, deciding between 'lifestyle choice'/'no other choice', and think where they can make the cuts across the board.
There are lots of these areas, e.g. 'child benefit caps'/ winter fuel payments, etc. might just be the beginning... steady as she goes Sir Keir!