Quoting from verywell.com:
“Portion Control Using the Plate Method
Keeping Your Food Portions in Line with Your Diabetes Management
Managing portion size is one of the best ways to control your eating habits and lose weight. That may require breaking some stubborn habits, though. Most people are accustomed to filling up their plates based how hungry they feel. However, if you have diabetes, you must think about the quantity of food you eat at each meal. Many people with diabetes find the plate method to managing portion sizes a helpful gauge when eating at a restaurant or other outing.
Though the plate method won’t be as accurate as counting carbohydrates, it will help you keep your food intake in general line with your overall diabetes management plan. Here’s how it works in three easy steps:
Take an average sized dinner plate and divide it in half. In one-half place non-starchy vegetables such as: spinach, broccoli, cauliflower, romaine lettuce, cabbage, carrots, tomatoes, onions, cucumber, beets and peppers. You can make a salad from a combination of these vegetables or just serve any one by itself. About one cup of raw vegetables is considered an appropriate serving size. One cup would be about the size of your fist.
Divide the other half of your plate in half again. In one quarter place your protein source, such as: 3 oz. of lean beef or pork, 3 oz. of skinless turkey, chicken or fish, tofu, eggs or cottage cheese. A 3 oz. serving is about the size of a deck of cards.
In the last quarter of your plate place your starchy foods such as: bread, potatoes, corn, beans, rice, tortilla, cereals or oatmeal. Serving sizes range from ½ cup of rice to a baked potato about the size of your fist.
The plate methods works best when you use a 9-inch plate versus the standard 12-inch dinner plate. While this method helps keeps portion control in check it is best used when you are away from home and can’t measure your food carefully.”
Sources: Create Your Plate. American Diabetes Association. http://www.diabetes.org/food-and-fitness/food/planning-meals/create-your-plate/