Xenia, as is so often the case, you are talking a Whole Bollock.
I am not working-class (you will have to guess whether or not that is true, and you have as much chance of getting it right as you do with every other of your sweeping generalizations.)
I have given a convincing legal argument which supports my belief that the OP is not a thief.
I could also argue - equally convincingly- that 'grazing' is a healthier way of eating than 'three square meals'.
I don't derive my self-belief (or any satisfaction at all) from whether my children can wait till meal-times to eat. I'm astounded that anyone does.
I think that worrying about these things - and in particular about what you and your kind think of me and my children - bespeaks a social anxiety that I cannot ever imagine feeling. But I'm very sorry if you do.
The reason that the middle-classes tend to be thinner is because they are far more likely to agonize over what their 'peers' think of them.
It is human nature to try and protect oneself from pain; if one knows one is being judged on one's weight, one has an incentive to vomit/starve/whatever, in order to avoid the emotional pain which comes from failing to make the skinny grade.
Other classes (including my own ) are far less likely to fear the opprobrium of their peers in such trifling matters as BMI. Their aspirations tend not to concern their dress-size. They are therefore more likely to be over-weight.
Whilst I know you are a system-generated junk-argument virus, I am slightly disappointed that they didn't programme in the fact that making judgments on the basis of class was as vulgar as it gets.