What's making me eat too much?

Is it your stomach or your brain that decides when you’ve had enough to eat? It appears that we don't select portions to match our energy needs – as a recent study shows, we underestimate how much we eat by one-third. That's 1,000 extra calories a day!

Which portion looks right to you?

Click the play button, then drag the player to add more food to your plates. Which portion of each food looks like an ideal size?

We don’t judge a portion size by how many calories we need in each meal, as a proportion of the day. Our memories of previous meals – and whether they filled us up – dominate our idea of what a portion looks like before we take the first bite.

Which soup will fill you up the most?

The fullness that we get from food isn’t just determined by calories. Texture, composition, even a label can play a role.

  • Chunky soup - Studies show that calories consumed as solids are considered more filling than liquids and people eat less later.
  • Low-fat soup - People often compensate for foods marked low-fat or low-calorie by eating more or eating again soon after.
  • High-protein soup - Meals that contain over 25% protein have been shown to increase the feeling of fullness. Meals with high-fibre pulses made people feel 31% more full.
  • "Fuller-for-longer" soup - One experiment showed that women who were simply told an ordinary smoothie would keep them full for longer felt less hunger for 3 hours.

The effect of tableware


Are you a member of the clean plate club? Well done! Most other people on the planet are, too. A study analysing diners in six different countries showed everyone eats about 92% of what’s on their plate. So the size of it matters.

Exposure to very large portions overrides our memories of normal portions. When test subjects were given a very large plate of food, one they could not finish, they ate significantly more than when they were given a smaller plate of food that they could not finish. Restaurants that specialise in excessive generosity are normalising overeating even when we don’t clean our plates.


A container size will influence how much we consider a portion to be. Even experts! At a party to celebrate a colleague’s success, what else would experimental biologists do but eat ice cream while running an experiment? Each nutrition expert was randomly given a large or small bowl and asked to help themselves to ice cream. The experts with the big bowls served themselves 31% more ice cream. A bigger scoop also caused them to increase their serving size by 14%.


The size and type of cutlery we use affects the size of our bites, and therefore the speed at which we eat. Eating quickly has repeatedly been linked with weight gain. Using a spoon rather than a fork increases our bite size and eating speed. Using unfamiliar utensils, such as chopsticks, slows eating down.


Watch out for this optical illusion. We always underestimate how much liquid short, wide glasses contain. Even experienced bartenders found it hard to judge measures when free-pouring into short, wide glasses – they over-poured by 20%. If you want to reduce your consumption of calories in drinks, ditch the tumblers and large wine glasses. (Or switch to water!)

I'll have what she's having

Is your portion size influenced by the company you keep? How often have you eaten out with friends and asked who’s having starters or puddings? We like to share food equally in company. But the effect can be even more subliminal.

The fat suit

One small study of 82 students (and one actress) showed the weight of our eating companions can affect us. In the study the actress ate lunch at a pasta and salad buffet with the group – only sometimes she wore a prosthetic suit that added 50lbs to her weight. No matter what she ate (more salad, less pasta, or vice versa) the people who ate with her consistently ate 30% more pasta and less salad when she was wearing the suit.

Eating to impress

Gender can also have an impact. Women in one study consistently chose lower-calorie foods from a cafeteria when eating with male companions than they did when they ate with female companions. This effect was greater if the group was bigger – women ate increasingly more in a large group of women but ate less and less if they ate with more male companions.

Of course, if you want to avoid overeating that doesn’t mean you should avoid dining with a particular size or sex of companion. The point is that many things affect how much we eat beyond the food itself, sometimes in a way that runs contrary to common sense. Understanding those influences is the best way to stick to your own portion size target.