stealing food/gorging/hiding evidence

my son has always done this. i address it, he gets upset, it stops for a while.... but since becoming a one wage family i'm finding the impact of his massive eating habit really tricky. hes fit and healthy - very tall and slim - this isn't about him being obese or anything - but its clearly not a great thing to do - to gorge on packets of crisps and biscuits and spoons of nutella etc.. his siblings hide their sweets and good stuff as they know he'll have it, which isn't fair, but for me, i don't want to hide things as i don't believe that's helping him deal with the issue - even though i'm not certain what the issue is.... i think its habitual.... i'm a little lost.

i read somewhere it could be like stimming - the sensation of chewing - so ive bought him gum - and ive advised him about what he should and shouldnt be eating - and when - but id really appreciate some better guidance if you have any experience of this..... thank you