No cake at work. But a shop across the road.
Steroids get you several ways round. Firstly, they should be taken with food, and that isn't usually at normal mealtimes, so it adds a couple of snacks on (I ignore this these days - the evidence is taking the whole dose in one is nearly as effective).
Secondly, it stimulates your hunger. So you want more food.
Thirdly, it depresses your mood, which, for a lot of people means resorting to food.
Fourthly, if you're taking oral steroid, it usually means that you're not doing as much exercise as normal (I'm a cussed bugger for this one where cycling is concerned), so what you do eat is more likely to turn to fat, which, if you're on them for any length of time, means you get depressed about your weight, exacerbated by the enforced snacking and lowered mood anyway, so.....
It's a very very tough cycle to break. I don't like oral steroids - they got me overweight in the first place when I was on them pretty much 50% of the time during my teenage years (when they play havoc with your hormonal development too, btw, which doesn't help mood/snacking etc), but they are bloody effective in clearing up asthma.