Adding conditioning to your powerlifting adds to the work your body has to recover from, and that means you have to feed it. Plenty of lifters add cardio, forget to adjust their fuel, and end up run down with stalled lifts. A little attention to how you eat around conditioning keeps it helping instead of draining you.
Conditioning Burns Fuel and Recovery
Every conditioning session, easy or hard, spends energy and dips into your recovery budget. If you add conditioning without adding any food, you are quietly cutting your calories at the same time you are asking your body to do more. For a lifter trying to maintain or build, that is a recipe for feeling flat. Account for the extra work in your eating.
Carbohydrate Powers the Work
Conditioning, especially harder intervals, runs on carbohydrate, the same fuel your hard lifting uses. If you are doing real conditioning volume, make sure your carbs are high enough to cover both. Eating a carb meal a couple of hours before a tougher conditioning session keeps your energy up, just like it does before a lift. Skimp on carbs and both your lifting and your conditioning suffer.
Protein Still Protects Muscle
Keep your protein where it belongs, around one gram per pound of body weight, even as you add conditioning. That protects the muscle you are working so hard to build and keeps recovery on track. If anything, more total work is a reason to be more careful about hitting your protein, not less.
If you add conditioning, add the fuel to support it. Keep carbs high enough for the extra work, hold your protein, and do not accidentally starve your recovery. Fed properly, conditioning makes you better. Underfed, it just digs a hole.