Recently I've been asked questions about portion size, so I thought I'd write a bit about this, as one person's portion is different from another person's portion.
I had a look at the government's website and it doesn't tell you the plate size that they use, which isn't overly helpful. Not only that, but plate sizes have increased in recent years, resulting in portion sizes increasing.
There are, however a couple of examples of eatwell plates that you can purchase online. These are 10 inches in diameter, including a rim. Take off half an inch for the rim and you're looking at a portion size of 9 inches diameter.
I measured this against the plates I have at home (see image to the left) and you'll see that the inner circle is approximately 8 inches in diameter, therefore portion sizes can be slightly larger than the inner circle of my plates at home.
Now, I'm not expecting you to have a tape measure handy every time you want to eat. So to make references a little easier, I used my hand and compared this to the plate.
As you can see from the image to the right, the inner circle is slightly larger than my hand (I have XS hands!), so you should be looking at serving a portion that is slightly bigger than my hand size.
I also found this really useful eatwell plate example from Western Sussex Hospitals. They provide the size in grams of portions and examples of healthy food.