Meal replacements control calorie intake by regulating the exact number of calories consumed per serving. The amount prescribed is based on an individual’s resting metabolic rate (RMR) which can be determined by a high-tech, body composition analysis scale that measures an individual’s resting metabolic rate. The resting metabolic rate is the number of calories burned in a 24-hour period of time. The body burns calories digesting foods, breathing, the heart pumping and during many other vital functions the body performs to sustain life. If the person is desiring weight loss, weight gain or weight maintenance, it is determined most accurately by their RMR. Medical grade meal replacements also maintain muscle mass, particularly while losing weight since they provide adequate protein intake while the body is in a fat-burning mode or ketosis. The vital importance of sufficient protein intake and few carbohydrates is so the muscle will be spared from being used for energy making it such that the only source of energy left is from stored fat. Sufficient protein also produces satiety or satisfaction of fullness as protein is the most satiating macronutrient among carbohydrates, proteins, and fats. Finally, meal replacements often supply a well-balanced meal with adequate protein, sufficient but minimal carbohydrates, and most likely the daily requirements of vitamins and minerals. Meal replacements are often a means to an end but can be used safely in any meal plan for any length of time and are often a convenient and easy way to ensure adequate nutrition.