Even ice-cream has to be actually pulled out of the fridge, scooped out of the punnet into a bowl. This may seem like a small hurdle - but it's obviously enough to keep you from eating.
Instead - try getting a bunch of non-perishable food (eg mixed nuts or dried fruit/trail mix) and leaving it in an open jar somewhere easily accessible (eg on the bench). Every time you walk past it - grab a small handful and nibble on it.
From there, you can progress to a bowl of pre-cut-up fresh fruit or veg (keep a lid on it so it doesn't gather flies) for a healthier option. (cut it up all at once at the beginning of the week - leave out a day's worth each morning).
...and that should get the ball rolling.
Recent brainstorming sessions at SIAI (with participants including Anna, Carl, Jasen, Divia, Will, Amy Willey, and Andrew Critch) have started to produce lists of rationality skills that we could potentially try to teach (at Rationality Boot Camp, at Less Wrong meetups, or similar venues). We've also been trying to break those skills down to the 5-second level (step 2) and come up with ideas for exercises that might teach them (step 3) although we haven't actually composed those exercises yet (step 4, where the actual work takes place).
The bulk of this post will mainly go into the comments, which I'll try to keep to the following format: A top-level comment is a major or minor skill to teach; upvote this comment if you think this skill should get priority in teaching. Sub-level comments describe 5-second subskills that go into this skill, and then third-level comments are ideas for exercises which could potentially train that 5-second skill. If anyone actually went to the work of composing a specific exercise people could run through, that would go to the fourth-level of commenting, I guess. For some major practicable arts with a known standard learning format like "Improv" or "Acting", I'll put the exercise at the top and guesses at which skills it might teach below. (And any plain old replies can go at any level.)
I probably won't be able to get to all of what we brainstormed today, so here's a PNG of the Freemind map that I generated during our session.