What was the most interesting was that the kids who didn't eat it didn't just sit there looking at it, dreaming of how good it would be to eat it but took steps to distract themselves from the temptation.
This is much more powerful than self discipline.
I think that the real value of the article's tips is that as you get used to not going on HN/Reddit or just avoiding other types of procrastination you will get used to not doing that and thus won't do it even if you remove the barriers.
I know that I myself have a very hard time to work (like, I almost _can't_) if I'm not interested by (or having fun with) what I'm supposed to do. But sometimes there's no choice and then I'm really, really not productive. In this case, disconnecting myself from internet is kind of mandatory if I don't want to find myself "procrastinating" on IRC, HN or reddit (I often go there unconsciously, by reflex!).