Does protein for breakfast keep you full?

03 October 2017

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Question

Is it true that a protein rich diet can help you to feel more full?

Answer

Chris Smith put this question to digestion specialist Gareth Corbett.

Gareth - There is medical evidence that shows that a higher protein diet will make you feel fuller for a lot longer. That’s been done in a meta-analysis, so that’s a study of lots of different studies to be able to tell us if that’s the case. That was based on looking at what people ate and then they scored their fullness in these various studies and so that’s been shown to yes, it does make you fuller for longer. But the more interesting question is actually why does it make you feel fuller longer rather than does it or does it not? Because anybody who’s a regular bodybuilder would answer that question of yes, of course it does because that’s what I do for my diet.

There is some science behind this. First of all just to think about how protein digest, because proteins are complex molecules made up of lots of amino acids. As you break them down, they become polypeptides, which are slightly longer chains of amino acids and peptides which is two or more amino acids, and then you have amino acids on their own. They’re basically the building blocks of life so we have to eat protein because that’s what most of our cells are put together.

Chris - It’s what we’re made of, isn’t it?

Gareth - It’s what we’re made of, exactly. We eat protein in the form of meat, eggs, for example and our body starts to break it down in the stomach with enzymes until it gets to its most simple form. Then it goes into this circulation through the wall of the bowel up into the liver called the” portal circulation.” Now the portal vein is a really important blood vessel. It carries basically all the stuff that goes into our mouths into our circulation via the liver which is like a big factory in the body; it does lots of stuff. It seems that along the portal vein there is a type of receptor which is like a little plug socket, if you like, which seems to be activated to say  “I am full -  I am satiated.” And it seems that that might be the mu-opioid receptor within the portal vein for those who are a bit more interested in it. It seems that by protein binding on those receptors you get an effect where the brain goes “oh, okay, I’m now full up.” So it seems to be something going on in the portal bloodstream as opposed to something going on in the GI tract, which is actually really interesting.

Chris - So would the ideal breakfast then be something like egg? Because people always used to say “go to work on an egg.”  That’s got a lot of protein in it. Would that be a good choice to have then?

Gareth - Based on the fact that we know that protein will make you feel fuller longer, it should keep you locked up till lunch, if you like, better than Shreddies, which is a carbohydrate breakfast.

Chris - What effect does that have? If you have a cereal rich, a very carbohydrate-rich breakfast. People usually add a bit of supplementary sugar to that as well. Does that sort of end up leaving you with a rebound hunger pang later?

Gareth - Yeah. And they pour fat over the top as well don’t they in the form of milk.

Chris - Well there is that and then there’s the whole kind of fruit juice that goes with it. A big dose of sugar with that too. Is there an impact of that?

Gareth - Yes. Carbohydrates are definitely processed much quicker and with carbohydrate diets you do feel fuller for less time compared with protein. So if you want it to say fine till lunch then I would have thought an egg is a reasonable thing to eat.

Chris - So, omelette, scrambled egg, and boiled egg and bacon. I’m doing my bit for the egg industry. With a bit of bacon on the side. There’s Gareth’s prescription as a gastroenterologist breakfast - a good way to start the day.

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