cut back (on something) = start eating or drinking less of something (because it is bad for your health)
- He used to smoke a lot but now he is trying to cut back and eventually quit it.
- You have to cut back on sugar if you want to lose weight.
- He really has to cut back on alcohol. He has started drinking too much.
- Salty food is tasty but we should all cut back on salt. It is not healthy.
- You can't cut back on fat if you eat meat every day.