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Portion distortion

Weight gain is fundamentally about energy balance. When more energy is consumed than the body requires, the result is excess body fat.

To put that into perspective, an extra 120kJ per day can contribute an extra 1.5kg weight gain per year. That is the equivalent of just one and a half Jatz biscuits added to your typical intake each day.

Although the solution might seem obvious — to eat less — the greatest challenge we have is that most people don’t even realise that they are eating too much.

Scientists have found that repeated exposure to images of food can influence what is accepted as normal, and over the past few decades, society’s perception of a ‘normal’ portion size has been creeping upwards.1

In 2016 researchers compared data from the 1995 National Nutrition Survey to the 2011–12 National Nutrition and Physical Activity Survey in an attempt to monitor these changes in portion sizes.2

From this they found that there have been notable increases in the amount of energy per typical portion and in some cases food portions were found to be 66% larger.2

‘Portion distortion’ is the term used to describe the perception that large portion sizes of foods are appropriate amounts to eat at a single sitting.3

Interestingly, the steady, yet dramatic ballooning of portion sizes over the past decades has occurred almost in parallel with the increasing prevalence of overweight and obesity.2,3

Although it is difficult to demonstrate this as a causal relationship, the implications of larger portion sizes are undeniable, and they have been documented frequently throughout the literature.1

In a 2015 Cochrane review of 72 studies, they established consistent evidence that subjects will consume more food and drink when presented with larger‐sized portions, packages or tableware.4

This phenomenon occurred equally amongst both men and women, regardless of their body weight and hunger levels.4

These researchers also found evidence to suggest that larger portion sizes can override self-regulation of energy balance and contribute to increased total energy intake across the day and ultimately lead to weight gain.2

These results indicated that the prevalence of over-estimating portion sizes might be subconscious and potentially more widespread than originally thought.5

Managing portion sizes

When it comes to weight management, there is an abundance of misleading information readily available, and with a growing obesity problem, it is important now more than ever for health professionals to make a concerted effort to provide homogenous advice to their patients.

1. Eat from smaller plates

Even serving less food on a large plate has been found to lead to less satisfaction from a meal,4 whereas eating from smaller plates has been found to be helpful in reducing energy consumption in the same way that eating from large plate sizes has contributed to excessive energy consumption.2,5,6

 2. Embrace the Healthy Plate Guide

Portion-control plates have been developed to allow individuals to better regulate their intake by providing clear visual cues about what amounts of particular foods should be on their plate. These tools have been demonstrated to improve weight loss initiatives and are an excellent place for patients to start out.1

3. Put away distractions

It is impossible to respect and listen to hunger and satiety signals provided by the body when distractions are present. This means turning off the television, putting the phone away and actually serving food on a plate instead of eating straight from the fridge or over the kitchen sink.

4. Practice makes perfect

It is important to understand and recognise what a healthy serving size looks like.5,6 Patients should be encouraged to use kitchen gadgets such as measuring cups, tablespoons, teaspoons or food scales to learn portion sizes recommended by the Australian Healthy Eating Guidelines.2 After some practice, patients should be able to put away their gadgets and rely on their intuition to know what an appropriate portion size is.

Weight management is a multifaceted and complex issue to tackle, and as such individuals should always be referred to a dietitian where possible.

But despite the endless possibility of causes, the consumption of large portions sizes has been highlighted as a specific cause for concern by recent research.

Therefore, health professionals offering patients generalised advice about controlling portion sizes is an effective, simple and reliable strategy to begin conversations about weight management.

Bridget Scrogings, Accredited Practising Dietitian


  1. Robinson E & Kersbergen I. 2018.  Portion size and later food intake: evidence on the “normalizing” effect of reducing food portion sizes. The American Journal of Clinical Nutrition. 107(4): 640–646
  2. Miaobing Zheng M, Wu J, Louie J, Flood V, Gill T, Thomas B, Cleanthous X, Neal B & Rangan A. 2016.  Typical food portion sizes consumed by Australian adults: results from the 2011–12 Australian National Nutrition and Physical Activity Survey.  Scientific Reports. 6, Article number: 19596
  3. Rolls, B. 2014. What is the role of portion control in weight management? International Journal of Obesity. 38 (1): 1–8.
  4. Hollands GJ, Shemilt I, Marteau TM, Jebb SA, Lewis HB, Wei Y, Higgins JP T, Ogilvie D. 2015. Portion, package or tableware size for changing selection and consumption of food, alcohol and tobacco. Cochrane Review.  viewed November 10 2019 <>
  5. Hetherington M, Birtill P, Caton S, Cecil J, Evans C, Rolls B & Tang T.  2018. Understanding the science of portion control and the art of downsizing. Proceedings of the Nutrition Society. 77(3): 347–355.
  6. Benton D. 2015. Portion Sizes: What we know and what we need to know. Critical reviews in food science and nutrition. 55(7): 988–1004





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