By Clare Murphy
BBC News health reporter
A lot on your plate: both bowls contain 525 calories but the spaghetti bolognese on the left is padded out with vegetables and will keep you fuller for longer
It may not be a licence for a liquid lunch exactly, but consuming foods high in water could be the key to losing weight, nutritionists say.
Dishes with a high water content, including pasta and rice - which absorb liquid - as well as soups and stews, appear to keep you feeling fuller for longer.
But don't be fooled into thinking you can simply down a glass of water with your lunch. Studies suggest the liquid has to be a key component of the meal you are eating, scientists from the British Nutrition Foundation (BNF) say.
At the same time padding out these meals with vegetables - which are high in both water and fibre - will mean you can eat more while in fact consuming the same amount of calories. And you shouldn't feel peckish an hour later.
So be liberal while using the grater over your spaghetti bolognese, as long as its carrots you're sprinkling.
Do the maths
ENERGY DENSITY CALORIES PER GRAM
Vegetable soup: 0.52
Baked beans: 0.81
Boiled egg: 1.47
Strawberries and cream: 1.6
You may need a calculator.
The BNF's advice is to use foods low in energy density to make up the bulk of your diet. These are foods lower than 1.5 calories per gram and include baked beans, boiled eggs, or vegetable stir-fry with noodles.
You can work this out by dividing the number of calories by the weight of your food. So your 180g sandwich with 360 calories has 2 calories per gram.
As such it falls into the category of medium energy density foods, which also include lasagne, pizza steak and salmon. "You need to control the portion sizes of these foods and eat them alongside lots of lower energy density foods," says Bridget Benelam, a nutrition scientist at the BNF.
Anyone for afters - these puddings both contain 215 calories
Meanwhile foods high in energy density such as crackers, biscuits, crisps, peanuts and chocolate should, perhaps unsurprisingly, be eaten in very small quantities.
However even when it comes to puddings, there's room to fill up.
Instead of a couple of pieces of chocolate, try a chocolate mousse, the BNF suggests.
And while you could go for a small bowl of strawberries and cream, go for mixed berries with low fat yogurt, crunchy oat cereal and honey.
The suggestion that foods high in water keep us feeling fuller for longer is increasingly substantiated by research.
The idea is that the combination of food blended with water empties more slowly from the stomach than solid food on its own with a glass of water to wash it down.
Pumping food with air may also increase feelings of being full.
Catherine Collins, a spokeswoman for the British Dietetic Association, said "feeding yourself fuller" was an interesting concept.
"We are getting to a point now where people realise that more fruit and vegetables are the way to go and more luxurious foods should be saved for indulgence.
"But people still need to take in all the major groups - and starchy foods, meat and fish have to play a role.
"Salmon for instance is an important source of healthy fats.
"However, it's good advice to pad out your meals with foods lower in energy.
"When you look down at dinner time, vegetables should be taking up a lot of room."