The serving sizes listed on food packages are supposed to reflect realistic portions. But like Romano’s pizza, some don’t. Serving sizes also fluctuate between products that should be comparable – 2 chocolate flavoured milks, for instance.

The result is that you can’t rely on serving sizes to determine if one food is healthier than another or use them to estimate the kilojoules you’ll actually eat. And that’s a problem in a country where two-thirds of the adult population is overweight or obese.

Nutrition panels

Since 2002, food manufacturers have had to provide consumers with nutritional information about products. This information appears in the nutrition information panel on food labels.

Within this panel, the nutritional values of the food – including its energy content, fat and sugars – must be listed in two formats:

• per 100g or 100ml
• per serving.

In theory, you should be able to use per serving information to figure out a food’s nutritional value based on a reasonable portion size. However, the serving sizes listed on food labels aren’t defined by a regulatory authority. They’re determined by the manufacturer. As a result, serving sizes can be inconsistent across comparable products. They can also be unrealistically small.

Tip: Use the per 100g or 100ml column in the nutrition information panel if you want to compare the nutritional value of different food products. Per serve information is useful if you’re looking at a single serve container (such as a pottle of yoghurt). In these instances, the per serve information gives you a better indication of the total energy and nutrients you’ll actually consume.

Comparison problems

Serving sizes form the basis of other nutritional information on food products. Percentage daily intake values, for example, often appear prominently on the front of food packages and in the nutrition information panel. These values are supposed to tell you the percentage of your daily energy needs – as well as other nutrients – in a single serving. But the percentages are misleading if the serving size is unrealistic.

Moreover, you can’t use the percentage daily intake figures to compare two products – even if they’re made by the same brand – because the serving sizes they’re based on aren’t equal. Kellogg’s Just Right Original, for instance, contains 7 percent of your daily energy intake and 13 percent of your daily sugar intake in a 40g serving. That seems slightly worse than Kellogg’s Coco Pops (6 percent of your energy, 12 percent of your sugar) until you realise the percentages for Coco Pops are based on a 30g serving.

Under review

In 2009, an expert panel was set up to review our food labelling laws. The panel’s final report, Labelling Logic, was published in 2011. It contains 61 recommendations, one of which is to make per serving information no longer mandatory unless the product contains a daily intake claim.

The report states: “Numerous studies have found the percentage daily intake system is confusing for consumers. A major issue is that it is based on inconsistent serving sizes, with different products and brands using different average serving sizes …”

However, the proposal to make per serving information voluntary won’t solve the issue of inconsistency. Consumers shopping for healthier groceries are already faced with dubious product claims (see “Food label claims”) and confusing nutrition information panels. Another food-labelling element that can be added or removed at the manufacturer’s whim won’t help.

In December, Food Standards Australia New Zealand called for submissions on the proposal for voluntary per serving information. The consultation period closed in February. If a decision is made to keep this information, we think serving sizes need to be standarised and monitored. Some manufacturer-defined serving sizes – and other labelling elements that depend upon them – are unhelpful.