We use cookies to allow us and selected partners to improve your experience and our advertising. By continuing to browse you consent to our use of cookies. You can understand more and change your cookies preferences here.


When you click on a retailer link on our site, we may earn affiliate commission to help fund our not-for-profit mission.Find out more.

30 Sep 2020

Are you eating too much breakfast cereal?

We carried out an experiment comparing how much cereal we eat to the recommended portion size on the box

Are recommended portion sizes too small, or are we eating too much? More than 120 people took part in our cereal experiment to find out.

Very few of us look at the recommended portion sizes on packaging when serving ourselves food - we go by instinct and plate up how much we think we need to satisfy our hunger.

But the results of our cereal experiment show that many of us are in for a shock, as recommended portion sizes are considerably smaller than the amount we tend to serve ourselves. Find out more below.

The Which? cereal experiment

To test how realistic cereal manufacturers' recommended portion sizes are, we enlisted the help of staff and members of the Which? Connect panel.

All 122 participants served themselves a 'usual' bowl of their cereal and told us the dry weight of their serving, the portion size that's recommended on the packaging and the type of cereal they were eating.

Our results show our volunteers served themselves, on average, 63% more than the recommended portion.

Cereal serving sizes: recommended vs actual

Servings of Bran Flakes most frequently exceeded the recommended portion size. The recommended serving is 30g, but in our experiment the average serving was 70g - more than double.

Servings of oats and pre-measured cereals such as Weetabix matched the recommended serving sizes most often.

Poll: Do you stick to the recommended cereal serving size?

Sticking to recommended portion sizes can be hard, especially as very few of us weigh out our food.

This isn't helped by inconsistent portion sizes.

The recommended serving size of oats varies between 40g and 50g, depending on the brand. The same applies for granola and muesli.

And the recommended serving of Kellogg's Cornflakes in the UK is 30g, but in the US it's a much larger 42g.

We're all different shapes and sizes, so a one-size-fits-all approach to portion sizes won't work for everyone.

Some of us need to eat more than others, and our daily energy needs depend on many things including our age, size and activity levels.

Yet nearly all of our volunteers - adults and children - served themselves more than the recommended amount of cereal, which begs the question 'who are the recommended portion sizes based on?'. 

Breakfast foods to avoid

Breakfast cereals are a quick and convenient meal in the morning, yet not all cereals are the same.

Many are packed full of sugar and akin to eating biscuits or sweet pastries. Try to avoid these.

You can use nutrition labelling on the front of the pack to tell at a glance whether your cereal is high in sugar. Try to avoid those with a red traffic light. 

Instead, go for unsweetened, high-fibre choices. Good examples are oats, Weetabix and Shredded Wheat.

If you want sweetness, add some fresh, frozen or dried fruit, which will provide extra vitamins, minerals and fibre.

Milk is a good source of calcium and protein. If you're opting for a plant-based milk, make sure it's fortified (has added calcium and other vitamins and minerals).

Traffic light labelling

Consistent and realistic portion sizes would help consumers and make front-of-pack nutrition labelling more accurate.

The recommended serving of Fruit 'n Fibre is 40g, but the average serving in our experiment was 90g.

  • 40g of Fruit 'n Fibre contains 152 kcals and 9.6g of sugar
  • 90g of Fruit 'n Fibre contains 342 kcals and 21.6g sugar

Front-of-pack labelling is a helpful tool, and traffic lights tell you at a glance whether your food is high, medium or low in sugar, fat, saturated fat and salt.

But the numbers are only useful if you stick to the recommended serving.

Recommended portion sizes need to reflect what we actually eat so we have the right information to make informed choices about what we consume.

We've found inconsistent and unrealistic portion sizes on a wide range of foods. Find out more in our look at serving sizes andportion distortion.