It's no secret that portion control is a huge element to any balanced diet; portion control and its healthy side kick, moderation.

But a new study by consumer watchdog Choice has revealed that serving sizes are increasing without us realising it - and food manufacturers' use of food labelling means that following the recommended serving sizes isn’t necessarily as sensible or straightforward as it sounds.

The bad news? When we think we're consuming one serve, we're likely eating more.

The report noted that in Australia, manufacturers determine the serving sizes but they are often inconsistent between comparable products, and even within the same brands, and some are simply unrealistic.

For example, a serving of Woolworths Home Brand Quick Oats is 30g but a serving of Freedom Foods Quick Oats is double that at 60g. And depending on what size of chip bag you reach for, 'serving size' can be 19g, 27g or 45g in the case of Smith's Chips Original.

And while many consumers would assume that a 300mL bottle of juice amounts to one serve, the study made example of Golden Circle Healthy Life Probiotic juice, whose bottle is actually 1.5 servings. Similarly, the labelling on a standard tub of yoghurt states it is 2.25 servings - not something obvious from the front of pack labelling.

Because of the 'flawed' nature of the manufacturers serving sizes, they "shouldn’t form the basis of a front-of-pack labelling system." Instead, Choice recommends a more useful and accurate "interpretive system", one which translates the relevant information already available on food labelling into colours, symbols, words or ratings.

"Based on consistent measures of products such as 100g or 100mL, this system will help consumers compare products at a glance and identify the healthier options more easily."

Read more of the study from Choice