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02. Diet and GLP‑1: What Studies Show About Protein and Fibre
Can meal composition influence the response of gut hormones? Research on protein and fibre offers interesting findings — and important questions.
In the second article of this series, we explore the relationship between diet, GLP‑1 and satiety. We distinguish findings from specific experiments from general recommendations for a varied diet.
Diet and GLP‑1: what are we actually studying?
GLP‑1 is one of the hormones through which the digestive system responds to nutrients. Studies investigate, for example, whether different meal compositions change its blood levels. That is only one part of the question.
It is equally important to establish whether someone feels less hungry, eats less at the next meal or experiences a long-term weight change. These outcomes do not necessarily follow automatically from a hormonal change. [1]
Three different outcomes: higher GLP‑1 levels, greater satiety and long-term weight loss are not interchangeable. A good study clearly states which outcome it actually measured.
Protein: what did a human study show?
In a randomised study involving eight healthy volunteers, researchers compared breakfasts high in protein, fat or carbohydrate. The meals had comparable energy content, volume and appearance.
After the high-protein breakfasts, researchers measured higher levels of GLP‑1 and PYY, another gut hormone. However, participants did not consume significantly less energy at the subsequent freely available meal. [1]
The finding supports a relationship between meal composition and hormonal responses. However, this small, short-term study cannot establish a guaranteed weight-loss effect for a particular protein-rich food.
Fibre, the microbiome and short-chain fatty acids
Gut microorganisms ferment certain types of fibre, producing short-chain fatty acids, known as SCFAs. One of these is propionate, which has also been studied in relation to GLP‑1 release. [2]
Researchers developed a special inulin–propionate ester that delivered propionate to the colon. Short-term testing in humans increased GLP‑1 and PYY levels and reduced energy intake. A longer part of the research followed 60 adults with overweight for 24 weeks and found less weight gain than in the control group. [2]
However, the preparation studied was not the same as ordinary dietary fibre. The findings therefore cannot be applied to every serving of oats or pulses, or to any fibre supplement.
Which foods contain protein and fibre?
The following table provides an overview of nutrient sources. It does not rank foods by their ability to ‘increase GLP‑1’.
| Group | Food examples | How to include them |
|---|---|---|
| Protein-rich foods | Eggs, fish, quark, plain yoghurt, tofu. | Combine with vegetables and other components of a varied meal. |
| Pulses | Lentils, chickpeas, beans, peas. | Add to soups, salads or main meals; they contain both protein and fibre. |
| Whole grains | Oats, wholegrain bread, brown rice. | Use as a breakfast base or side dish according to individual needs. |
| Vegetables and fruit | Broccoli, carrots, apples, berries. | Include a variety throughout the day. |
What makes sense in an everyday diet?
We do not need to know our GLP‑1 levels to choose a varied range of foods. WHO recommends that adults consume at least 25 grams of naturally occurring dietary fibre and at least 400 grams of vegetables and fruit daily. Recommended carbohydrate sources include whole grains, vegetables, fruit and pulses. [3]
These are general healthy-eating recommendations, rather than amounts intended to achieve a particular hormone level.
Breakfast inspiration
Plain yoghurt or a suitable higher-protein plant-based alternative, oats and fruit. Protein content varies between plant-based alternatives — check the label.
Main-meal inspiration
Lentils, tofu, fish or eggs, with vegetables and an appropriate side dish. These are examples of food combinations, rather than a ‘GLP‑1 diet’ with guaranteed results.
Are there ‘natural GLP‑1 foods’?
The term appears in online articles, but it can create inaccurate expectations. Food can influence the body’s own hormonal response. That does not make it a substitute for treatment or a food with a proven effect comparable to a medicine.
When encountering claims such as ‘this food switches off hunger’, look for the original study: did it examine the same food, an ordinary portion and human participants? Did it measure only the hormone, or also food intake and long-term body weight?
Frequently asked questions
Does protein increase GLP‑1?
High-protein breakfasts had this effect in the small human study described above. However, participants did not consume significantly less energy at the next meal. The finding cannot be generalised to every food or every person. [1]
Does every type of fibre have the same effect?
It is not appropriate to attribute the results of one preparation to all types of fibre. The propionate study tested a specific ester designed to deliver the substance to the colon. [2]
How much fibre does WHO recommend for adults?
At least 25 grams of naturally occurring dietary fibre daily. This recommendation concerns overall nutrition, rather than guaranteed GLP‑1 stimulation. [3]
Does higher GLP‑1 automatically mean weight loss?
No. A hormonal change, feelings of satiety, energy intake and long-term weight changes are different outcomes. Each needs to be investigated separately.
Do I need to buy special ‘GLP‑1 foods’?
The general recommendations described here can be met with everyday foods such as pulses, whole grains, vegetables and fruit. The ‘GLP‑1’ label alone does not demonstrate a product’s quality or effectiveness. [3]
Simply put
Protein and fibre feature in research on gut hormones and satiety. However, the overall diet matters when planning meals. A single measured hormonal change does not establish a guaranteed effect on body weight.
Next topic in the series: The gut microbiome and GLP‑1 — what we know about fibre fermentation and short-chain fatty acids.
Continue to article 03: The gut microbiome and GLP-1 →Curious about what’s in food supplements?
Our Nutraceuticals Buying Guide lets you compare ingredients across the KINGRAY range and check the amounts per daily dose and any precautions for use.
Educational purpose: This article does not replace individual nutritional advice, medical assessment or treatment. If you have a medical condition or dietary restrictions, adapt your diet according to a healthcare professional’s recommendations.
