A serving size is a measured amount of food or drink, such as 2 to 3 ounces of meat or 1 cup of milk. Serving sizes are standardized so that nutrient levels in each serving are comparable. Consumers and dietitians may use serving sizes to determine how much of the recommended daily levels of certain substances (vitamins, minerals, fats, calories, cholesterol) a particular food represents.

Dietitians often use visual approximations to help consumers determine by sight the appropriate serving size for many foods. Rather than using a scale or measuring cup, people can estimate the correct serving size by comparing the food to commonly used items. For instance, one serving of meat, fish or poultry (3 ounces) is about the size of a deck of cards.

Serving sizes may vary depending on how certain foods are prepared (e.g., raw, cooked, canned), as well as the nutrition guide or source consulted. Servings listed on a Nutrition Facts Label (found on the back of nearly all packaged food products) are different from those used as the basis of food guidelines for healthy eating plans, such as food guide pyramids like MyPyramid. They were developed by different government agencies to serve different purposes.

Serving sizes should not be confused with portion sizes or helpings of food, which are the amounts of food typically served or eaten during a meal or snack. Portions can vary from meal to meal or person to person. Although the terms are sometimes used interchangeably, serving sizes are usually much smaller than portion sizes. Most foods are sold and consumed in larger portions than is recommended by government standards. For example, the average bagel consists of two serving sizes, pasta is almost five servings and a steak may be two and a quarter servings.

Many experts believe large meals have contributed to obesity because consuming more than the recommended serving sizes adds excess calories, salt and fat to the diet. All of this potentially contributes to bigger waistlines and an increased risk of developing chronic diseases such as heart disease, stroke, high blood pressure (hypertension), diabetes, osteoporosis or obesity.

Large portion sizes in restaurants and at home have also resulted in consumers who are increasingly confused about the amounts of food they should eat. Becoming familiar with what counts as a serving size can help consumers make food choices that help them maintain a healthy weight and body.

Serving sizes are standardized amounts of foods (e.g., 2 or 3 ounces of meat or 1 cup of raw leafy vegetables) that are small enough to easily compare nutrient and calorie levels among different foods. Thus, each serving size for a particular food group contains approximately the same amount of vitamins, minerals, cholesterol, salts and other substances. Serving sizes are used as the basis of daily dietary recommendations for the following:

• Diet plans and menus
• Food guide pyramid
  

  

• Nutrition facts labels required by the U.S. Food and Drug Administration (FDA)

The typical amounts of food consumed by many Americans (also called portion sizes or helpings) far exceed the serving sizes recommended in federal dietary guidelines. For example, microwaved popcorn contains 4 ounces in a bag. If the entire bag is consumed as a snack, it can represent almost an entire day’s recommended servings of grains. Similarly, a typical bagel can contain the equivalent of 4 ounces, or 4 servings, of grains.

The U.S. Department of Agriculture (USDA) developed standard serving sizes in 1992 with the release of the Food Guide Pyramid, which recommended Americans eat a certain number of servings daily from each of six food groups (grains, vegetables, fruits, milk, meat/beans, oils/sweets), such as 6 to 11 servings of grains. USDA serving sizes were determined based on one or more of the following factors:

• Nutrient content
  
  
• Typical portion sizes (as indicated in national food consumption surveys)
  
  
• Ease of use
  
  
• Tradition (previous food guides)

However, in 2005, the USDA issued a revised version of the pyramid called MyPyramid. Instead of using servings, MyPyramid recommends eating foods in precise amounts (e.g., 6 ounces of grains per day). The new food guide pyramid is an interactive, individualized tool that provides the types and amounts of foods a person should eat each day based on factors such as age, gender and activity level.

Although MyPyramid does not utilize serving sizes, the standardized measurements are still widely used by dietitians and consumers. Many popular diet plans also use serving sizes in their dietary recommendations. However, each may define serving sizes differently for the same foods. For example, one plan may define a serving of rice as one-third cup, whereas another may define it as one-half cup (the USDA standard). In addition, studies have found that many people have difficulty interpreting and properly using the nutrition labels found on food packaging.

Different serving sizes may also appear on the nutrition facts label required by the FDA and found on the back of nearly all packaged food products. These labels indicate the number of servings contained in the package. These serving sizes are standardized based on the average amount people say they eat (called the “reference amount”), as reported in national food consumption surveys. On these labels, a serving of cooked pasta (one cup) is not the same as a serving of cooked pasta as described in many food guides (one-half cup, the USDA standard).

Consumers are advised to compare the stated serving size amount with what they actually eat. If they eat three times the serving size, then they also consumed three times the calories, fats, sugars and other nutrients indicated on the label.

Most Americans do not carry weight scales or measuring cups with them to restaurants and thus may have difficulty determining what a standard serving size represents. The American Dietetic Association (ADA) began using common household items as references for what a serving might look like. For example, 3 ounces of meat on a plate (one serving) might look like a deck of cards. A one-cup serving of raw vegetables would be able to fit into the palm of an average woman’s hand.

The following examples of serving sizes and their approximate visual equivalents were determined by the U.S. Department of Agriculture (USDA) and ADA. They are applicable to adults and children over the age of 2 years.

There are no recommended serving sizes for drinking water, which has no calories. However, many health experts agree that healthy adults may need 11 to 16 cups (approximately 2.7 to 3.7 liters) of water per day to ensure adequate hydration. Total water intake includes water from a variety of sources, such as juice, milk, broth, tea, coffee or soda.

People who want to eat healthier and/or lose weight may find it helpful to pay attention to serving sizes while eating a variety of foods. Even the most nutritious foods, when eaten in excess, can contribute calories and may lead to unwanted weight gain. Learning to recognize what a serving of food looks like on a plate can take practice.

Bulk foods labels – such as those on flour, rice and cereal – use common terms such as cup, fluid ounce, tablespoon or teaspoon. The serving sizes for these items are based on what comes closest to the amounts indicated in consumption surveys. For items that are sold whole and divided after purchase (e.g., cakes, pizza, pies), the serving sizes are typically listed in fractions, such as 1/4 pizza. Items that are divided into individual units (e.g., eggs, bread, sliced meats, hot dogs) use the units as the serving size, such as one egg or one slice. Items like cookies may be listed by the piece (e.g., 1 serving = 6 cookies) and are derived by taking the weight of the amount of cookies typically consumed and determining the number of cookies needed to get the equivalent weight in different packages.

The following tips may be helpful in determining appropriate serving sizes and altering eating habits:

• Practice measurements. To become more familiar with appropriate serving sizes, try weighing or measuring foods at home and visually compare them to similarly sized common household items. Then, place the measured serving of food on a plate or in a glass to visualize the serving size. Meat is typically weighed after trimming and cooking, without bones.
  
  
• Eating out. If a restaurant serves large portions, diners can order from the appetizer menu or share an entrée with a companion. Some consumers also ask for half the meal to be wrapped "to go" or ask for the lunch-size meal (even during dinner). Salad dressings or other sauces may be served on the side to avoid exceeding the 1 tablespoon serving size limit.
  
  
• At home. Rather than placing serving bowls or trays of food on the table (which encourages second helpings and overeating), dietitians recommend placing only the appropriate serving sizes on meal plates.
  
  
• Read labels. Carefully reading nutrition facts labels can help consumers determine if the serving size listed on the package is appropriate for their meal plan.
  
  
• Between meals. When snacking or eating between or before meals, the rolls, appetizers or drinks all contribute to the daily caloric intake and should be taken into account.

Some experts believe that plates and cereal bowls with serving-size markers can help people to eat foods in more appropriate amounts. A Canadian study found that obese people with diabetes are more likely to lose weight and improve their glucose levels if proper portion sizes are clearly marked on their tableware.

Federal dietary guidelines are intended for children over the age of 2. Parents with questions about appropriate serving sizes and feeding schedules for infants and toddlers should consult with their child’s pediatrician.

The U.S. Department of Agriculture (USDA) has developed MyPyramid, an interactive tool designed to help tailor eating plans based on an individual’s age, gender and activity level. MyPyramid replaced the USDA’s Food Guide Pyramid in 2005, and recommends the amounts of foods to be eaten daily from each of six basic food groups (grains, vegetables, fruits, oils, dairy, meat/beans). However, rather than recommending serving sizes, the new guide recommends specific measurements of foods in cups or ounces.

Preparing questions in advance can help patients to have more meaningful discussions with health professionals regarding their conditions. Patients may wish to ask their doctor or registered dietitian the following questions related to serving sizes:

1. What serving sizes are appropriate for my condition?
   
   
2. What are the appropriate serving sizes for my son or daughter?
   
   
3. How can I reduce my daily caloric intake?
   
   
4. What impact do serving sizes have on my weight loss goals?
   
   
5. If I want to gain weight, is increasing serving sizes the appropriate way for me to accomplish this?
   
   
6. How can I determine appropriate serving sizes when I’m dining out?
   
   
7. Can I eat all of my daily recommended meat servings in one meal or should I space them out over the entire day?
   
   
8. If I follow a vegetarian diet, how can I alter my serving sizes to ensure I’m getting enough iron and protein each day?
   
   
9. If I eat smaller serving sizes will I consume enough calories each day to maintain my current weight?
   
   
10. Do you recommend a particular exercise plan for me that would complement my eating plan?