This is a tricky question and comes down to how good your diet is. If you do HITT your gonna be burning up more cals and your body is primarily gonna be looking for glucose but it won't be getting it cause your on low-carb so it's either gonna go for fat or protein. That being said if there's not enough fat in the diet you could be losing muscle and all the gains you've made on weight training could be washing away. You also could take advantage of nutrient timing. Higher carbs around workout times to minimize protein loss. If your on a low-carb diet you can also do steady state cardio. Low intensity is primarly burning fat but less calories. There's advantages and disadvantages here. Advantage is your more likely to hold onto your muscle, disadvantage is your overall calories buring is low. Just some things to think about based on your goal. I prefer hitt for higher carb diets and lower intensity cardio for low carb diets cause I believe the emphasis should be to keep and build muscle at all times. The more muscle you have the higher your metabolism will be.