I am not familiar with insulatard but would think if you're receiving the same blood sugar numbers with less insulin than I can't see why not. However I would not compromise my blood sugars and let them run higher just to cut back on insulin. If I wanted to cut back on insulin I'd cut back on carbs.
I have no idea what kind of diet your GP or cardiologist want you on. Diet and insulin should be discussed with them of course.
Losing weight on insulin need not be hard as long as your diet is right. There are foods that can make us insulin resistant therefore requiring more insulin. For ME those foods are all grains, all dairy, too many nuts ( especially peanuts ), too much protein and saturated fats.
My diet is 80% fat but mostly plant fats like avocado, olive oil, olives, mayonnaise and some macadamia nuts, pumpkin seeds or pecans in moderation. I don't eat chicken skin, bacon, fatty sausages, lots of butter etc.
I used to eat a lot more saturated fats and had high cholesterol. Switching to plant fats brought that right down. Carbs clog arteries and raise cholesterol so I stick with only above ground veggies for those.
All that being said, if you find the right diet insulin will not stall weight loss.
Most importantly is to take enough insulin to achieve good blood sugar control.