What is a Diet Meal Substitute? Diet Meal Replacement by Protein Works is a protein-rich, nutrient-rich meal replacement shake designed to contribute to weight loss. With only 250 calories per shake, full of 20 grams of protein and slowly digestible carbohydrates. This combination creates a feeling of fullness, while keeping the calorie count low. The key to success with a diet is to persevere. That's why all our shakes taste great. Soft, delicious and designed to keep you going. With the added advanced ingredients, it is a perfect accompaniment to your weight loss journey.