work some fat off

work off

1. To shed excess body fat through physical exercise. Usually used with terms "fat," "pounds," or "weight" along with mitigators like "some," "a bit," "a few," etc. I've made it my New Years resolution to work some weight off at the gym. He's started running in the evenings to work off a few pounds.
2. To help metabolize or expend the calories from some meal or piece of food with exercise or other physical activity. In this usage, a noun or pronoun can be used between "work" and "off." I know that was a pretty heavy breakfast, but we'll work it off on our hike later on. I feel like I need to go on a two-hour bike ride to work off that cake!
3. To expel or shed some negative emotion or mental state with exercise or other physical activity. In this usage, a noun or pronoun can be used between "work" and "off." I was so furious after the meaning that I had to go to the gym for two hours just to work it off! You should try swimming laps—I found that it really helped me work off my anxiety.
4. To free oneself from debt through paid work. In this usage, a noun or pronoun can be used between "work" and "off." I had to take a second job on the weekends to help work off my student loans. I forgot to bring my wallet with me to the restaurant, so I had to work the bill off washing dishes in their kitchen.
5. To use something as a template or point of guidance. Architects worked off the original 12th-century drawings to authentically recreate the Gothic cathedral. Hey, I'm just working off the instructions they gave me—it's not my fault if something is wrong!
See also: off, work
Farlex Dictionary of Idioms.

work some fat off

 and work some weight off to
get rid of body fat by doing strenuous work. I was able to work a lot of weight off by jogging. I need to work off some fat.
See also: fat, off, work
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • work off
  • baby fat
  • puppy fat
  • fat and sassy
  • lard
  • lard (something) with (something)
  • lard with
  • fat chance