No, portion sizes food labels do not indicate how much we should eat

The Australian Healthy Eating Guide sets out how much we should eat from each food group. If we consume the recommended number of "standard servings" of each food group for our age and gender, we are in a good position to be healthy and well-balanced.
But what is a standard markup? And does it match what's on our food labels?

Served standard

Despite the name, standard servers are not very standard, even in the Australian Healthy Eating Guide. Portions can be described by energy (kilojoules or short kJ), which is contained in one serving, units of foods such as "a medium apple" or "a slice of bread", by weight or by volume like a cup.
A "markup" also differs between each of the food groups and even within the food groups.
A serving of cereal is about 500kJ. This is an English muffin, but only half a roll. Or it could be half a cup of porridge, a quarter of a cup of cereal, or three quarters of a cup of wheat flakes.

A serving of milk is 500-600kJ, that could be a cup of milk, but it's only three quarters of a cup of yogurt or half a cup of ricotta. Hard cheese is defined by slices, two slices being in one serving, provided each slice has about 20g.

Serves on food labels

Almost all packaged foods in Australia have nutritional information boards. This includes information to help us choose better foods.
The exact details depend on the food. However, you must at least specify how much energy (kJ), protein, fat (total and saturated), carbohydrates (total and sugars) and salt (sodium) are contained in the product. This content is always given twice per 100 g (100 ml for liquids) and serving.

The portion of the label, however, has nothing to do with the standard portions of the Australian Healthy Eating Guide. The serving size on the label is not a recommendation on how much you should eat - it is determined by the manufacturer. It depends on how much a person normally consumes or the size of the unit in which the product is consumed.

This can be very different from a standard markup. For example, the labeled serving size on a candy bar might be "one board" - 53 grams of chocolate at 1,020 kJ. However, according to the Australian Healthy Eating Guide, one serving equals half a bar (25 g) or about 600 kJ, and it is recommended that you do not over-confin (junk food) to one serving a day.

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Compare portion sizes between brand and pack sizes

In Australia, there are no rules on how these portion sizes are set. One serving may not be the same in similar products or brands of the same product.
This can make the comparison of products difficult. The serving size of a soy sauce in a brand may be, for example, one-tenth of a soy sauce from another manufacturer.
To increase the confusion, a serving does not necessarily reflect the serving size: how much a person consumes in a meal or sitting.

For example, a 250g packet of white microwave rice could contain two 125g portions. This is because the manufacturer expects two people to be served. But one of these labeled portions are almost two standard servings of cereal.
To make it even more confusing, a 450g family pack with four servings of 112g each could be labeled in the same rice brand. That's 10% less than the portion size in the smaller package. However, it is believed that a family of four could divide the pack during a meal. In this pack, a serving size equals about 1.7 standard servings of cereals.

How labels affect our food choices

Although labeled portion sizes are not related to standard portions or to the recommended amounts that should be consumed, consumers often interpret the labeled portions as recommendations for serving size or for adhering to dietary guidelines, according to studies.

Studies show that the given portion size has an impact on how much people eat. Larger portions on labels may seem like a large portion is recommended, causing people to eat more or serve themselves more. This has been shown on several foods, including biscuits, cereals, lasagna and cheese crackers.
However, with some foods, such as lozenges, larger portion sizes can compromise your health, resulting in lower consumption or smaller portion sizes. This is likely because the large number of kilojoules in the data per serving is noticeable.

So, what should you do?

Since portion sizes may vary by product and manufacturer, it is easiest to use the data per 100g or 100ml instead of the data per serving for product comparison. However, think of the actual weight or volume you need as a consumer when considering how to fit your daily intake.
The recommended diet for an average adult is based on consuming 8,700 kJ of energy per day. To gain so much energy from a balanced diet, these are 50 g protein, 70 g fat and 310 g carbohydrates. We also want to go for 24 grams or less of saturated fats and 30 grams or more of fiber.

However, needs are differentiated by life phase, activity level, gender, current weight and weight goals. There are online calculators to estimate your needs.
Memorizing portion sizes and guidelines can be difficult. To simplify this, you can print a copy of the Australian Healthy Eating Guide and save the portion sizes to display when preparing food.