Well, in theory, police should be one of the carreers where it should be hard to actually gain weight, in a way similar to military.
In praxis, they spend 5-10 hours a day sitting in a front seat of a car, eating sweets and drinking bad instant coffee with a lot of sugar.
I'm not sure, but I think most of police personel have to pass yearly physical exams and drills here to stay employed (and to get emploeyd at the first place) here, doesn't US have something similar? I mean... It makes sense, fit cop can actually catch people instead of empting a clip into them and won't snap and beat up drunken people when they call him fat.