The problem with portion sizes

Recommended portion sizes on foods are inconsistent, often unrealistic and can leave people confused about how much they should eat - or under the impression they are consuming less fat, sugar or salt than they actually are.

On-pack nutrition labels, with their traffic light system for an at-a-glance look at how healthy food is, may give you a misguided picture if you don't pay close attention to the recommended serving size, which is often smaller than you might expect.

For example, nearly 80% of Which? members, when surveyed in May 2023, thought a supermarket sandwich-based meal deal would count as one serving. But the drink and snack element often contains two.

Some products have different suggested serving sizes depending on the size of pack you buy, or where you buy it from.

And it's not just confusing serving recommendations. The trend for bigger plates and glasses also encourages us to eat more, as do super-sized restaurant portions.

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You've been served (too much)

Nutrition labelling on the front of food packaging tells you how many calories and how much sugar, fat and salt you'll consume if you eat the recommended serving. 

It's meant to help you manage your intake, but given that most people don't weigh out their food and aren't that good at estimating what a portion should be, it's likely they're overconsuming.  

When we asked people to estimate the recommended portion size for a range of popular foods in a survey, they often assumed it was more than the suggested serving size on the pack.

Of 1,265 Which? members surveyed in May 2023, more than half thought a 225g packet of halloumi sold in supermarkets contained between two and four servings. It actually contains seven.

And 79% thought a sandwich meal deal was one serving. The sandwich usually is, but you'll want to look twice at your drink and snack choices, which often contain two portions.

Snack sizes

We may all have our own idea of what's a reasonable amount to pluck from a box of chocs or a big pack of crisps, but the recommended serving on the label is often vanishingly small.

Almost a quarter of people in our survey thought a tube of Pringles contained four portions of crisps but in fact it's meant to be between six and seven. 

The same number also thought an 80g bag of Joe & Seph's popcorn contained two portions, but it's meant to feed four. 

It can be hard to visualise how much a serving size given in grams actually is - as we found when we asked people to measure out cereal portions in 2020.

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Mismatched portions

It becomes more confusing when manufacturers have different recommended portion sizes for similar items - or even for the same product when sold in different packs.

A 300g pack of Dell Ugo tomato and mozzarella tortelloni states it contains two portions, but a near-identical product from M&S, its 300g cheese and tomato tortellino, states it contains three portions.

With both chocolate and crisps, we found serving size differed depending on the pack you bought, even for an otherwise identical product.

For Cadbury's Dairy Milk, recommended serving size ranged from 20g to 33.5g depending on if you bought a standalone snack bar, multipack or a big bar, and Walkers Ready Salted crisps ranged from 25g (for a small bag in a multipack) to 45g for a 'grab bag', with variations in between for other bag sizes.

Bigger plates, bigger portions

Bigger portions that we have when eating out can skew our view on what's normal at home.

For example, a Pizza Express Classic American pizza in a restaurant is 343g and one pizza equals one portion.

The same pizza can be bought in the supermarket in two sizes - 250g and 458g. The recommended portion for each is half a pizza, but that leaves you with three wildly different serving sizes.

Plates, bowls and glasses have grown bigger over the decades too, and again restaurant trends influence our home habits. 

In the 1950s, a standard dinner plate used to be 25cm wide, whereas now the norm is 28cm. Some new sets are so big, in fact, that they don't fit properly in microwaves or kitchen cupboards.

Similarly, thirty years ago a glass of wine in a restaurant or pub was 125ml but, while some bottles still recommend this serving, you won't often see that size offered on menus. A standard glass is now 175ml and a large is 250ml - and they're served in bigger glasses too.

This combination means we become accustomed to over-pouring. We put this to the test, asking 229 people to pour themselves their usual glass of wine or juice and measure how much they poured. Around half of respondents poured themselves more than the recommended amount - in some cases more than double.

The largest glass of juice served was 400ml - nearly three times the recommended serving size of 150ml - while the largest glass of wine poured was 275ml.

Part of the issue with drinks is that we don't consider liquid calories in the same way as those that we eat. They don't fill us up, so it's easy to overconsume without realising. 

Having a 400ml glass of orange juice would mean consuming 35g of sugar (vs 13g in a standard serving) - more free sugar than the maximum recommended limit for adults to consume in a day. 

Similarly, for the wine, you'd be consuming more than double the units of alcohol. Whilst it may not seem like much as a one-off, over time it can add up to a substantial creeping increase in how much you're drinking without necessarily realising.

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How to manage your portions better

Most of us don't look at recommended portion sizes on packs, we eat what we want or judge to be a portion.

To some extent this is understandable, as we're all different shapes and sizes and have different energy requirements. How many crisps we want as part of a lunch, versus as a standalone snack on the go, may well differ.

But nutrition labelling is designed to keep you informed about what you're eating. If the stated portion sizes are unrealistic, or hard to compute, it won't help, and could even give you a false impression that something is healthier than it actually is.

Portion control tips

• Check the portion size listed on the label, rather than just glancing at the traffic lights, to get a clearer picture of what you're eating. 
• If you regularly eat a snack, and aren't sure what a recommended portion looks like in practice, try measuring it out,  so you have a clearer idea of where your portion fits in.
• If you're trying to cut back, consider if giant crockery is making life harder for you. Switching to smaller plates, bowls and glasses where possible is a simple way to help manage portion sizes without feeling like you're being shortchanged.

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