Why and how does protein keep me feeling fuller for longer?

Have you ever wondered why foods and snacks high in protein seem to keep you full for an extended period? This article covers the physiological reasons why high-protein foods and high-protein snacks can keep you feeling satisfied.

Appetite and Hunger Hormones Roam NZ Australia

The Physiology of Fullness

Before we examine how protein specifically makes us feel satisfied and full, let's take a look at some of the hormones and neural signals that are activated when you eat.

  • Ghrelin: Often dubbed the "hunger hormone," ghrelin is produced in the stomach and signals the brain to initiate eating. When your stomach is empty, ghrelin levels rise, telling your brain it's time to seek out food.
  • Leptin: Produced by fat cells, leptin has the opposite effect of ghrelin. It signals to the brain that you're full and should stop eating. Leptin levels rise after eating and stay elevated for a period, helping you avoid overeating.
  • Peptide YY (PYY): This hormone is released in the gut following food consumption and plays a key role in inducing a sense of fullness. The release of PYY is influenced by the types of nutrients ingested, with both fat and protein notably boosting its production as food enters the digestive system.
  • Insulin: Primarily known for regulating blood sugar, insulin also plays a role in feelings of fullness. Released by the pancreas after eating, particularly when consuming carbohydrates, insulin helps cells absorb glucose and signals the brain to suppress hunger. However, its effectiveness can be influenced by factors like insulin sensitivity, making its role in hunger and satiety complex.

    People with insulin resistance, a condition often seen in type 2 diabetes and obesity, may not respond to insulin's satiety signals as effectively, which can lead to increased hunger and weight gain.
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How protein affects these pathways

Protein has a unique effect on these hormonal pathways. Unlike carbohydrates and fats, which are digested relatively quickly, protein takes longer to break down. This slower digestion rate leads to a more gradual release of ghrelin, helping you feel full for longer. 

Moreover, protein-rich foods stimulate a quicker release of leptin and PYY. This is especially true for vegan high-protein meals, which often contain plant-based proteins that are rich in fibre, further enhancing the feeling of fullness.

The Thermic Effect of Protein

Protein has a higher thermic effect compared to fats and carbohydrates. This means your body uses more energy to digest, absorb, and metabolise protein.

While this is often cited in discussions about weight management, it's important to note that the thermic effect is just one small piece of a much larger puzzle. It's not a silver bullet for weight loss or management, and its impact is relatively minimal when compared to other factors like overall caloric intake, the quality of your diet, and physical activity.

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The role of amino acids

Proteins are made up of amino acids, and some of these can directly influence our satiety levels. For example, the branched chain amino acid, leucine has been shown to stimulate leptin release, further enhancing the satiety effect of protein-rich foods.

Note that if you are looking to maintain your lean muscle mass, it's best to consume at least 3 to 4 grams of the amino acid leucine and the amino acid lysine per day. Roam Protein has 1.8g of leucine and 1.6g of lysine per serve - almost half your daily requirements [1].

Practical Applications

Understanding these physiological pathways can help you make smarter food choices. For instance, incorporating high-protein options like Roam Protein into your diet can help you manage your appetite more effectively. This is particularly beneficial for those who are active or are looking to manage their weight.

Feeling full isn't just about the quantity of food you eat; it's also about the quality. Opting for high-protein options can help regulate your hunger hormones, keeping you full and energised for longer periods. Whether it's a high-protein snack or a vegan high-protein meal, understanding the science of satiety can guide you in making healthier, more satisfying choices.


[1] Attia, Peter. (2023) Outlive: The Science and Art of Longevity, pg. 333.

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Plant-based and Delicious. Over 22 grams of protein per serve.
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