Along with your starches like potatoes and whole grains, Dr. McDougall recommends increasing the amount of non-starchy veggies you're eating. This includes cooked and raw greens, carrots, cabbage, broccoli, cauliflower, yellow squash, courgette, peppers, celery, cucumbers, mushrooms, and tomatoes. These have a low-calorie density and are packed with fibre and water, which means eating them will fill you up for not a lot of calories.
Note that Dr. McDougall says you shouldn't only eat non-starchy veggies because you need starches to feel satiated. This is a starch-based diet, after all! Eating only raw salads and steamed broccoli will leave you hungry and feeling deprived, and you'll end up falling off the plan completely.