Portion Size vs Serving Size

Written by Talia Cecchele

There is a lot of confusion about how much to eat to maximise health, especially when it comes to the portion sizes of food. Serving size (or suggested serving size) and portion size are often used interchangeably, despite having different definitions.

What is a Serve?

A serving (or suggested serving) is a standard amount of food. Serving size is used for educational purposes in dietary guidelines, on nutrition labels or the amount of food you are served in a restaurant.

When it comes to nutrition labels and packaged food, the manufacturer sets the food label’s serving size based off an estimation of the amount of food most people would typically eat. It is not based on science or the standard serves in national dietary guidelines such as the Eat Well Guide in the UK or the Australian Dietary Guidelines (confused yet?).

The serving size of the core food groups in dietary guidelines (listed below) differ between countries slightly, however as a general guide, we use the following:

It is important to note that the suggested serves for each of the core food groups (listed above) differ based on age and gender. For example, for an adult female it is recommended to have the following each day to optimise nutritional intake and ensure a well balanced diet:

Vegetables - 5+ serves daily

Fruit - 2 serves daily

Dairy - 2-3 serves daily

Meat & alternatives - 2-3 serves daily

Carbohydrates - 6 serves daily

These serving sizes are based off the nutritional composition of foods and our knowledge of the types and amounts the human body needs to thrive. It is just a starting point.

What is a Portion?

A portion is the amount of food you choose to eat. This could be more or less than a suggested serving. For example, the nutrition label might suggest two weetabix for one serving, but if you eat three or four weetabix, that is your portion size. Or a standard serve of carbohydrates is 1 slice of bread, but you would eat 2 slices in a sandwich (bringing you to 2 our of the recommended 6 serves of carbohydrate foods a day).

Why are Serving Sizes Used?

The key to eating a well balanced diet is to eat a wide variety of foods in appropriate amounts for your nutritional needs. Making healthy food choices means choosing to eat some foods more often and in larger amounts, and others less often and in smaller amounts. Some foods for physical nourishment, and others to nourish the soul.

It is important to be aware of serving sizes as eating too much or not enough of any type of food can impact your health negatively and/or increase risk of health problems. Having a balanced diet is the best way to maximise your health from a nutritional perspective.

Barriers to Using Serving Size

  1. Every person is unique and as such, the suggested serves of food groups or on food labels can only be used as a guide to dictate portion size. Nutritional requirements differ according to age, sex, body composition, metabolic rate, activity levels and health status such as if someone has a medical condition

  2. Similar products can provide different serving sizes. Sizes can be calculated in grams, milliliters, cups, spoons, pieces or numbers e.g. 2 weetabix. Depending on how much you choose to eat and how you build a meal, your portion size may be different to the serving size

  3. Overtime, our perception of what a typical portion size is and what is served has changed. We call this portion distortion. Food and drink portions have become larger over the decades, including many of those foods that the majority of people aim to be eating in smaller amounts and less often including muffins, soft drinks, chocolate bars and ice cream. Research has proven time again that the more food we are served, the more we eat.

  4. Including a serving size on is not a legal requirement for packaging. Mandatory back of package labeling in the UK requires the nutrition declaration for energy and six nutrients (fat, saturated fats, carbohydrates, sugars, protein and salt). The nutritional values must be listed per 100g/ml and energy listed in both kJ and kcal. It is important to note that some suggested serving sizes might be influenced by meeting claims about certain nutrients e.g. fat or sugar.

  5. Obsessively following serving sizes and nutritional information can lead to the development of disordered eating behaviours for some people such as calorie counting, weighing and measuring foods or tracking food intake. Serving sizes should only ever be used as a guide.

Serving sizes are just a guide and the portion size you choose to eat will depend on how hungry you are and any other nutrition goals that you have.

How to Navigate Serving Sizes and Portion Sizes

Suggested serves and nutrition labels can have a positive place in helping people choose between products to make healthier choices and guide portion size. Here are some tips to make navigating this confusing part of nutrition a little easier:

  • Subscribe to the TC Nutrition newsletter to download our free portion guide on How to Build a Balanced Plate

  • You could use measuring cups short-term to visualise a suggested serving size and guide your portion size while working on intuitive eating. This can be a helpful tool to use at the start, but ultimately what we encourage is to work on intuitive eating and listening to your body

  • Because serving sizes can vary between similar products, it is best to compare products using the per 100g/ml information when comparing products and key nutrients like saturated fat intake or sugars. You will need to consider the actual volume of food you will consume when comparing products and how this fits into your lifestyle and nutritional goals

  • Learn to be an intuitive eater! This is the final step on the journey to normalising your relationship with food. There is no black and white rules when it comes to nutrition, so it is an important skill to learn to be flexible with eating and dietary choices. You can learn more about what normal eating is here.

Navigating intuitive eating and portion sizes can be difficult especially if you have been engaging in disordered eating or dieting for many years. If you need support or help, please reach out and connect with us by completing an enquiry form.

Talia Cecchele

Registered Dietitian



Talia Cecchele Nutrition is a team of registered dietitians specialising in eating disorders and disordered eating. We aim to bring balance back to nutrition, help you to break free from food rules and find food freedom. To enquire about private consultation please fill out a contact form.


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