Serving Size vs Portion Size: How are They Different and Why Does it Matter?

Two phrases you’ll often notice in nutrition conversations are serving size and portion size. These may sound similar, but in fact they are quite different. And each term has layers to its definition to be considered. So, how are they different and why does it matter?

Serving size definitions are three-fold. 1) Serving size literally means ‘the amount you are served,’ as at a restaurant or Nanna’s house for Sunday brunch. 2) It also refers to dietary guidelines made by the USDA of recommended servings for each food group to assist in healthy decision-making for the average American. 3) Lastly, it includes ‘recommended’ serving size listed on nutrition facts labels by manufacturers or on recipes by authors of magazines, cookbooks, blogs, etc. 

My Plate dietary guidelines by the USDA.

A portion size literally means ‘the amount of food you actually eat.’ For instance, though you may order one pasta carbonara at The Cheesecake Factory, and the size you are served may be larger than what you’d need to feel satisfied, so you may eat half and box the rest. The portion size is more individualized. It is the portion of food you eat to meet your specific needs from day-to-day. If you are following a meal plan from a dietitian, the portions they’ve set out for you for your meals and snacks considers your individualized needs (your age, height, sex, weight, exercise/movement, medical conditions, lab values, ect.) If you’re eating intuitively, it may be more fluid and dynamic. For instance, you may find yourself eating a smaller dinner if you had a larger afternoon snack or you may find you’re authentically hungry for twice the portion of dinner you took the day before because you went on a long bike ride with a friend. In a nutshell, portion size is based on your unique health needs.

A portion size is the amount food you actually eat based on intuitive decision making or with support of a dietitian to honor your unique nutritional needs.

So what’s the best advice I can give you when navigating serving and portion sizes? Here it is:

  • Reference the USDA dietary guidelines, as needed, as a foundation.
  • Adjust the portion size to less or more based on your individual needs. If you’re unsure of your needs and/or this feels overwhelming or confusing, reach out to a qualified nutrition professional. (While Dietitians are the only title recognized by the government and insurance agencies as nutrition experts, a Diabetes Educator, or Doctor of Naturopathy or Functional Medicine may be some other options to consider. Be wary of those who call themselves nutritionists or health coaches who do not have at minimum a bachelor’s degree in the subject.) 
  • Scrap the serving size recommendations on Nutrition Facts labels. They just aren’t reliable. Food manufacturers have a long history of manipulating serving sizes to trick consumers into thinking their food is ‘healthier.’ They adjust the serving size to optimize the way calories, sugar, fat, protein, sodium, fiber,  vitamin, or mineral content appears to the consumer, in hopes you will think buying their product is a good choice. Sorry not sorry, but in no world is eating ⅓ cup of Ben and Jerry’s or 6 tater tots a normalized serving size for an average adult. 

Scrap the serving size recommendations on Nutrition Facts labels. They just aren’t reliable.

So, how can we sum this all up? 

  1. Serving sizes from the USDA’s dietary guidelines are a helpful starting place, as they are made by nutrition experts for the average person. 
  2. Serving sizes from manufacturers are not reliable. 
  3. Portion sizes are unique to the individual and can be adjusted from the serving size, formed intuitively, or with the support of a nutrition professional. 

Using serving sizes and formulated portion sizes doesn’t go against mindful or intuitive eating practices, especially if you struggle to identify your body’s cues of what and how much to eat.

While intuitive eating is great, it’s not always realistic for everyone. Using serving sizes and formulated portion sizes doesn’t go against mindful or intuitive eating practices, especially if you struggle to identify your body’s cues of what and how much to eat. If this is the case for you, they can be especially useful. Overall, serving sizes and portion sizes can just be another tool to keep in your self-care toolbox. 

With Kindness for You Body,

Lindsay Midura, RDN, LD, RYT

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