its 290grams of fat loss a day for 4 weeks, and your taking a heavy stack, you will kill it. Don’t starve yourself, just adjust your calories and train hard, it takes 3500 cals per 1kg of fat loss, so 18 pounds equals just over 8kg to loose, 8kg equals 28000cals all up.
If you adjust your daily cals to reduce down by 500 below maintenance, and than do an extra 500 cals of steady state cardio every day (roughly a 2-2.5hr walk) that should do it. It will be hard, but you could easy achieve it, just have discipline. The reduction and walking will equal around about 14000-17000 cals, but the stack and your regular training will amount for the rest.