Honestly, if you're on a strength program right now, and you want to keep your gains (and perhaps continue to get stronger), keep on with the strength program.
Adjust your diet. Remove all/most of your starches and sugars, keep the fruit intake up, and nothing crazy with volume. If you're squatting/deadlifting/pressing/pulling intensely enough, your metabolism will be high and shifted towards burning fat and preserving muscle.
So to sum that up, eat a bit less, especially of carbohydrate (adjusted to your own tolerance), and keep trying to gain strength.