This is a common roadblock when it comes to losing weight. Most people understand that eating an apple and some nuts as a snack is more nutritious than a chocolate bar, but they’re not hitting their goals and, in some cases, manage to gain weight. Welcome to the world of portion sizes – the key to unlocking this mystery.

Right now, over two-thirds of Australians are overweight or obese. Why? It’s a complex problem, but easy access to processed food, less physical activity and increased portion sizes are some of the key reasons.

Portion size vs. serving size

Portion size is the amount of food you actually consume in one sitting, as opposed to serving size which is the amount of food listed on the nutrition label (this is often – but not always – based on the recommendations of the Australian Dietary Guidelines). These two are often confused and thought of as interchangeable, but that’s definitely not the case.

Eating healthy and nutritious food but having no understanding of portion size is like treading water – you won't see progress (and may end up going backwards). Eating uncontrolled amounts of any food (yes, even the good stuff) will overload the body with unnecessary kilojoules – this is where we introduce the third player in this game: portion control. Portion control is consuming the amount of food that your body actually needs to function well.

If you’re eating healthy food but overdoing the portion sizes, you won’t see a change in the scale – even healthy foods eaten in excess cause weight gain. Portion control is key as it allows you to consume the amount of food that your body actually needs, and eliminates unnecessary consumption of kilojoules/overindulging.

How serving sizes are used

Serving size is used in two different ways – the first is recommended serving sizes as listed within the Australian Dietary Guidelines. For example, a serving size of broccoli is half a cup. The average Australian needs five to six servings of vegetables like this per day. A serving of oats is half a cup, with the recommendation being four to six serves from the grains and cereals group per day.

The other way serving size is used is on food labels. In Australia, serving sizes are determined by the manufacturer – this makes it tricky for the average consumer because serving sizes are often inconsistent between similar products, or even within the same brand. A box of cereal lists 40 grams as a serving size, another 50 grams. Food companies have to list all the nutrients and energy content per 100 grams as well as per serving size, so the 100 grams column is the one that we should refer to when comparing products.

Take note: Studies indicate people serve themselves much more than the recommended size on the packet.

Portion size

As we mentioned above, portion size is different to serving size. It’s the amount you actually eat. So, one portion of cereal may in fact be two to three servings.

Portion sizes are increasing – both in the home and when dining out, and it’s obvious that larger portion sizes result in increased kilojoules. When people are presented with larger portion sizes, people will eat more, instead of stopping when they feel full.

The three main factors that influence how much food is eaten (portion size) are:

1. The actual amount of food presented

The amount of food presented or served has a big impact on the portions people eat. Unsurprisingly, studies show that people eat more when they are presented with larger portion sizes. In the 1950’s, McDonald’s offered just one size of soft drink (210ml), which is just under a cup. These days, the options go up to a whopping 950ml, which is nearly a litre of soft drink with about 25 teaspoons of sugar. This is well over the World Health Organisation’s recommendation of a maximum of 6-12 teaspoons per day. French fries and hamburgers are now two to five times larger than those originally served. Some restaurants serve up one main meal that could easily serve two.

2. Plate and glass size

At home, the size of our bowls and glasses have steadily increased, with the surface area of the average dinner plate has increased by 36% since 1960.

One study showed that by increasing the size of the dinner plate from a 25 to a 30-centimetre plate, people ate 22% more food. People pour into short wide glasses rather than tall narrow glasses. Also, larger utensils mean people eat more – try eating cereal and meals with a teaspoon.

3. Packaging

Larger packages encourage overeating. Often, larger packages contain more than one serving, which makes it really hard for people to follow the recommended serving sizes. For example, a large bag of chips may contain 7-12 serves, but most people won’t stop at one serve, they’ll eat the whole bag.

Unlike other animals, if humans overeat one day, they don’t adjust the next which leads to a continual pattern of overeating.

My top seven strategies to help control portion sizes

1. Eat from smaller plates and bowls, use small spoons for serving and eating, try using a dinner plate which is the span of your hand.
2. Pre-portion your foods and don’t eat directly from a box, bag or container that contains multiple servings – put the amount of food you want into a small bowl and put the rest away.
3. Serve portions on individual plates in the kitchen, instead of putting serving dishes with large amounts of food on the dining table. This means people will be less likely to go for seconds.
4. When dining out, share an entrée and main with your company, rather than two main meals – that way you get to taste two different meals and will be eating less than a whole main meal.
5. Choose the smallest container or cup when ordering takeaway, because they usually contain more than enough food and are high in kilojoules.
6. Don’t be tempted by value meals or supersized portions – they may be good value for money, but they’ll contain more kilojoules.
7. Wait 20 minutes until serving more food – it takes 20 minutes for the stomach to tell the brain that it’s full. Chances are, after 20 minutes, you’ll feel full and less likely to go for seconds.

References

Clemons, R (2014) Are you being fooled by portion creep? Available at https://www.choice.com.au/health-and-body/diet-and-fitness/weight-loss/articles/increasing-portion-sizes

Division of Nutrition and Physical Activity. Research to Practice Series No. 2: Portion Size. Atlanta: Centres for Disease Control and Prevention, 2006. In

Hollands GJ, Shemilt I, Marteau TM, Jebb SA, Lewis HB, Wei Y, Higgins JPT, Ogilvie D

2015, Portion, package or tableware size for changing selection and consumption of food, alcohol and tobacco (Review)

Issue 9 Available at http://www.thecochranelibrary.com

McCrory MA, Fuss PJ, Hays NP, Vinken AG, Greenberg AS, Roberts SB. (1999) Overeating in America: association between restaurant food consumption and body fatness in healthy adult men and women. Obesity Research 7(6):564-571.

National Heart, Lung and Blood Institute (2015) Portion Distortion Available at https://www.nhlbi.nih.gov/health/educational/wecan/eat-right/portion-distortion.htm

Rolls, B, Morris, E and Roe, L (2002) Portion size of food affects energy intake in normal-weight and overweight men and women Am J Clin Nutr vol. 76 no. 6 1207-1213

Wansink, B (1996) Can package size accelerate usage volume?, Journal of Marketing, Vol 60 (July 1996) 1-14. Available at http://mindlesseating.org/pdf/PackageSize-JM_1996.pdf

Young, L and Nestle, M, (2002) The Contribution of Expanding Portion Sizes to the US Obesity Epidemic Am J Public Health. February; 92(2): 246–249.

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