The Difference Between 'Serving Size' and 'Portion Size'

We underestimate a serve of veggies, yet overestimate a serve of chocolate.

Raise your hand if you've ever looked at the back of a cereal or pasta packet to see the 'serving size' is a measly half a cup -- which is nothing compared to your regular serving of a bowl -- and sighed.

Or, on the other hand, do you eat two leaves of lettuce and count it as a serve of vegetable?

You're not alone. Many Australians are confused about the difference between portion size and serving size, and this confusion actually leads us to overeat or under-eat certain foods.

The difference between serving size and portion size

Serving size: refers to a set amount of food which is based on the amount of energy in the food. It helps to compare the energy in foods, such as bread or cereal.

Portion size: refers to the amount a person should eat, depending on the individual and their daily energy needs. A 'portion' may be more or less than a 'serve'.

One serve of nuts is 30 grams.
One serve of nuts is 30 grams.

As LiveLighter dietitian and campaign manager Alison McAleese told HuffPost Australia, "a portion size refers more to the amount that a person should have in their day".

"For a younger woman, for example, their portion of cereals and breads would be six serves. The portion size depends on the individual, whereas the serving is set."

The confusion around portion and serving sizes is partly because these two terms haven't been very well explained. And there are two direct consequences of this misunderstanding: we either overestimate a serve, or underestimate a serve.

"We tend to underestimate what one serve of vegetables is, but overestimate what a serve of chocolate is," McAleese explained.

"For example, people who try to cut down on their serving sizes to the amount that's written on the packet might end up having a tiny bowl of cereal or just one piece of toast. This would mean they are likely to get hungry soon after."

While a serve of muesli is 30 grams, you may need two serves to make up your breakfast portion.
While a serve of muesli is 30 grams, you may need two serves to make up your breakfast portion.

As a result of only eating half of our breakfast, this hungriness can lead to reaching for a not-so-healthy snack and overeating on junk food across the day.

"A serve on the pack of a breakfast cereal is 30 grams. Most people need around six serves of grain-type foods a day, so you could definitely have 60 grams at breakfast and that would be fine," McAleese said.

"The other way it can work is, if people are unaware of portion sizes in general, you can end up overeating on foods."

So, which foods do we generally overestimate and underestimate?

1. Vegetables = underestimate

"Definitely vegetables. Most people think to have five vegetables a day, but it's actually five serves of vegetables, and people might not realise what this is," McAleese said.

"A serve of veggies is half a cup of cooked vegetables or one cup of raw vegetables, or half a medium potato. You want to have five of these serves a day. It's about the weight, rather than the type, you're having.

"Only about four percent of Australians eat enough vegetables, so pretty much all of us can benefit from eating more of them."

2. Breakfast grains/cereal = under- and overestimate

If you're someone who tries to stick to the small serving size when you prepare your porridge, muesli or healthy cereal, you may be under-eating. Conversely, if you fill up a big bowl, you may be overeating.

"Breakfast cereal is one which people often underestimate, just because of what's written on the pack," McAleese said.

"It's quite hard to work out how much you're having so I'd recommend, once or twice a year, to weigh out the amount you're having, or measure it out with a cup. Two serves (around 60 grams) would be a fine serving size."

Keep this handy guide in mind for measuring portion sizes.
Keep this handy guide in mind for measuring portion sizes.

3. Meat = overestimate

Most Australians eat more meat than they probably realise. High intake of red meat, however, is linked to an increased risk of bowel cancer.

"Often the way meat comes cut or sold in a pack (for example, a 500 gram pack with two pieces of meat) makes people think that's the amount they should have," McAleese said.

"However, a serving size of meat is around 100 grams of raw meat, which is about the size and thickness of your palm. It's a lot smaller than what most people would have. This is for poultry and red meat. Fish would be a little bit bigger at 120 grams.

"People might worry this is too little or that their plate would be half empty, but this is where you fill your plate up with vegetables."

Include more plant-based protein foods like falafels, tofu and legumes.
Include more plant-based protein foods like falafels, tofu and legumes.

4. Chocolate = overestimate

Unfortunately, that Mars Bar or block of chocolate isn't considered a 'serve'.

"A chocolate bar, which looks like one portion, is around 1,000 kilojoules and this is actually two serving sizes of chocolate," McAleese said.

"In terms of healthy eating guidelines, the Australian Dietary Guidelines recommend we only have, at the most, two serves of junk food or 'discretionary food' each day."

If you're eating one of those chocolate bars a day, along with alcohol, sugary drinks and butter or fats (which also count as junk food), you can see how quick and easy it is to over-consume these foods.

"For chocolate blocks, all the different blocks have different sized squares. Again, you want to look for 500-600 kilojoules -- that would be a serve," McAleese said.

"For a plain block of milk chocolate, a serve is around four small squares."

Yep, this is probably too much.
Yep, this is probably too much.

5. Spreads and condiments = overestimate

When you're making a peanut butter sandwich or drizzling tomato sauce on your chips, it's not unusual to use up to a tablespoon of product.

"One serve of peanut butter or mayonnaise is around 10 grams, which is a heaped teaspoon," McAleese said.

While nuts and natural nut butters are healthy, the recommended daily intake of nuts is 30 grams, which means peanut butter can quickly add up.

6. Nuts = overestimate

Nuts are full of healthy fats and plant protein -- however, it is easy to go overboard and consume a lot of energy in one delicious sitting.

"Nuts are a food people tend to keep their hand in the bag for 20 minutes and the whole bag is gone," McAleese said. "Thirty grams is a serve, which is about 20 almonds or 15 cashews."

A daily serving of 30g of nuts is recommended.
A daily serving of 30g of nuts is recommended.

7. Fruit juice = overestimate

"Fruit juice is often sold in 500ml bottles, which is definitely more than we should be having," McAleese explained.

"A serving size of fruit juice is 125ml, which is only half a cup. Even with this, we recommend to only have juice occasionally."

8. Pasta = overestimate

"People often overeat on pasta because they don't think about what an appropriate amount is," McAleese said.

"A serve of pasta is half a cup of cooked pasta, and that's about the size of your fist."

But remember, you may need more than one serve of pasta at mealtime.

"You might want to include one or two serves of grain foods (like rice, pasta or bread) at each of your meals, but in between meals, instead of eating more of these foods, have fruit, yoghurt, dips, nuts and vegetables."

Tip: add lots of veggies to your pasta sauce or mix zucchini noodles with the spaghetti.
Tip: add lots of veggies to your pasta sauce or mix zucchini noodles with the spaghetti.