Why Protein Makes You Feel Full Faster

by Sara Suchy Editor

We have heard that high-protein meals seem to fill people up faster. But why? Healthcentral breaks down the science behind protein and its benefits for weight loss and satiety.

plate after eating image

Feeling full, but why?

Scientists have long known that meals high in protein seem to make people feel full faster, but until now they have never been able to pin down exactly why. Research published in the journal Cell seems to have cracked the code. But first, it’s probably helpful to understand how your body tells you it’s full.

man digestive health image

All about communication

The food you eat is modulated through mu-opioid receptors (MORs) on nerves found in the walls of the portal vein – a major blood vessel that drains blood from the gut. Food modulation is simply the process by which your body communicates to your brain that you have just eaten something. How food is modulated will dictate how full a specific food makes you feel.

friends having lunch image

How you ‘feel full’

When stimulated, these MORs in the portal vein enhance food intake by telling the brain to eat more. When the MORs are blocked or suppressed, the brain is triggered to limit food consumption; resulting in that ‘full feeling’ after big meals.

beans image

It’s in the proteins

What scientists found in the Cell study is that the products of digested protein — peptides — can actually block the MORs, which, as we noted, curbs the appetite. Specifically, these protein-created peptides send signals to the brain that are transmitted back to the gut. The gut is then stimulated to release glucose, which suppresses the desire to eat. Studies are now underway in humans to treat obese people with binge eating disorder with a blocker of the MOR system.

lab mouse image

Proven in mice

To tease out exactly what causes the protein-induced ‘full-feeling’, scientists used mice that were genetically engineered to lack the MORs. When these mice were fed high-protein foods, the peptides did not stimulate the normal release of glucose that would happen in mice with MORs, nor did the genetically altered mice show signs of being full. This pointed to the MOR response as the key in determining the body’s satiated, or “full”, feeling.

nuts and seeds image

What you can do

MORs are also present in the neurons lining the walls of the portal veins in humans, so high protein foods will make you feel full. To take advantage of your body’s food modulation response to proteins, make protein a part of every meal.

High protein foods.

High-protein foods

The best sources of high-quality protein to include at each meal and snack are animal protein sources such as meat, poultry, seafood, eggs, and dairy products such as milk, cheese, and yogurt. Packed with protein, these foods will help you to feel fuller for longer so that you aren’t hungry soon after a meal.


Plant-based protein foods

The proteins found in plant-based foods such as nuts, seeds, beans, and soy products can also help to fill you up. Add nuts, seeds, or beans to your salad to increase the protein content of your meal. Add a nut butter such as natural peanut or almond butter to your apple slices to provide a satisfying snack.

eating relaxing dinner image

Slow down

Finally, it also helps to enjoy your meals and snacks slowly. Food modulation takes time so there is a natural lag between the moment you start eating and the moment your brain begins to sense that it is full. Eating slowly will help you avoid overeating.

Sara Suchy
Meet Our Writer
Sara Suchy

Sara is a former editor for HealthCentral.