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Guillermou's avatar
Guillermou
May 16

The evidence described is conclusive: high dietary fiber intake is consistently associated with a lower risk of obesity and better body weight control. The mechanisms are multiple and act in the gut, energy metabolism, and appetite regulation:

Regarding energy expenditure, bacterial fermentation and colonic metabolism require energy, and some of the calories from fiber are lost to bacterial growth and metabolic heat.

The small and large intestines consume energy primarily for muscle contractions (peristalsis and segmentation), active transport of water, electrolytes, and nutrients, and fiber fermentation. Although the intestine weighs little (1 to 2 kg), it is one of the most metabolically active tissues. It is estimated that the gastrointestinal tract consumes approximately 10% of basal energy expenditure. For a daily intake of 2000 kcal, the total energy used by the digestive system is 150–200 kcal/day.

The digestive organs (intestines, pancreas, etc.) represent <6% of body weight but consume 20–35% of the body's total energy expenditure.

It's important to note that this depends heavily on the type of fiber. Fermentable soluble fiber, such as inulin, pectin, and beta-glucan, provides 2–4 kcal/g of fiber, while insoluble fiber, such as cellulose and wheat bran, increases fecal volume and provides 1 kcal/g. Short-chain fatty acids (SCFAs), particularly butyrate, are key energy sources. 70% of the energy in colon cells comes from butyrate produced by bacteria. Fermentable carbohydrates induce metabolic thermogenesis in humans. The energy metabolism of the intestinal epithelium depends on glucose, amino acids, and fatty acids. Short-chain fatty acids (SCFAs) produced by fiber fermentation are a significant energy source for the colon. This means that some energy is lost as heat during bacterial fermentation.

This means that some energy is lost as heat during bacterial fermentation. Energy balance by fermentation of the type of fiber fermentation: wheat bran very low, cellulose low, psyllium low-moderate, beta-glucans moderate, pectin and inulin high.

https://pubmed.ncbi.nlm.nih.gov/12461672(2002)

https://www.ncbi.nlm.nih.gov/books/NBK223593/?utm_source=chatgpt.com (2011)

https://www.nature.com/articles/srep31917 (2016).-

https://www.mdpi.com/2072-6643/10/3/275 (2018).-

https://www.sciencedirect.com/science/article/abs/pii/S0924224418307878?utm_source=chatgpt.com (2019).—

https://pmc.ncbi.nlm.nih.gov/articles/PMC7019254/ (2019).-

https://pmc.ncbi.nlm.nih.gov/articles/PMC6360548/ (2019(.-

https://pmc.ncbi.nlm.nih.gov/articles/PMC10334151/?utm_source=chatgpt.com (2023)

https://academic.oup.com/ijfst/article/58/5/2216/7807788?utm_source=chatgpt.com&login=false (2023).-

https://pmc.ncbi.nlm.nih.gov/articles/PMC11826063/ (2024).--

https://www.ncbi.nlm.nih.gov/books/NBK597379/ (2025).—

https://pmc.ncbi.nlm.nih.gov/articles/PMC11826063/ (2025).-

https://www.ncbi.nlm.nih.gov/books/NBK53478/ (2025).-

https://pmc.ncbi.nlm.nih.gov/articles/PMC11826063/ (2025).-

https://www.frontiersin.org/journals/nutrition/articles/10.3389/fnut.2026.1769785/full?utm_source=chatgpt.com (2026).-

https://www.frontiersin.org/journals/pharmacology/articles/10.3389/fphar.2026.1738562/full?utm_source=chatgpt.com (2026).—

https://pubmed.ncbi.nlm.nih.gov/41423309/ (2026)

https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2026.1753136/full?utm_source=chatgpt.com (2026).-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Other factors involved in weight control:

1. Increases satiety and reduces calorie intake

Fiber (especially soluble and viscous fiber) slows gastric emptying and increases the feeling of fullness. This reduces appetite and the total number of calories consumed at the next meal. In addition, fiber stimulates intestinal satiety hormones that act on the brain to decrease hunger.

Clinical trials have shown that high-fiber diets significantly increase satiety and reduce spontaneous energy expenditure.

2. Decreases the energy density of the diet

Foods rich in fiber (vegetables, legumes, fruits, whole grains) contain fewer calories per gram, facilitating body weight control. 3. Reduces rapid glucose and insulin absorption

Fiber slows down carbohydrate digestion and reduces glucose and insulin spikes after eating, leading to less fat storage and improved insulin sensitivity.

4. Nourishes the gut microbiota

Fiber reaches the colon and is fermented by beneficial gut bacteria, producing short-chain fatty acids that regulate energy metabolism, reduce metabolic inflammation, and increase satiety hormones.

5. Improves the composition of the gut microbiota associated with leanness

Diets rich in fiber promote bacteria associated with lower adiposity and inflammation, such as Akkermansia and Prevotella.

Regarding the type of fiber:

----Soluble and resistant starch fibers are the most effective for controlling appetite and improving the gut microbiota. Fiber (especially soluble and viscous) slows gastric emptying and increases satiety hormones such as GLP-1 and PYY, thus reducing the amount of energy consumed. • By forming a gel in the stomach and intestines, fiber slows down glucose absorption

, reducing blood sugar and insulin spikes and promoting better energy metabolism.

---Insoluble fibers work more by increasing intestinal volume and accelerating transit.

---Fiber fermentation produces SCFAs (saccharide-rich fatty acids) that improve energy metabolism and reduce fat accumulation.

https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1160746/full?utm_source=chatgpt.com (2023).-

https://pubmed.ncbi.nlm.nih.gov/37815013/ (2023).--

https://www.nature.com/articles/s41575-023-00891-z?utm_source=chatgpt.com (2024).--

https://www.nature.com/articles/s41579-024-01108-z?utm_source=chatgpt.com (2024).--

https://link.springer.com/article/10.1186/s40168-024-01975-x?utm_source=chatgpt.com (2024).—

https://pubmed.ncbi.nlm.nih.gov/39163556/ (2024).--

https://www.nature.com/articles/s41579-024-01108-z?utm_source=chatgpt.com (2025).-

https://pubmed.ncbi.nlm.nih.gov/39390291/ (2025).—

https://www.sciencedirect.com/science/article/abs/pii/S0985056225000500?utm_source=chatgpt.com (2025).-

https://faseb.onlinelibrary.wiley.com/doi/full/10.1096/fj.202502040R?utm_source=chatgpt.com (2025).--

https://www.nature.com/articles/s42255-025-01356-0?utm_source=chatgpt.com (2025).-

https://www.reddit.com/r/ScientificNutrition/comments/1rn8u12/resistant_starch_intake_facilitates_weight_loss/?utm_source=chatgpt.com (2026).-

https://alimentosecuador.com/fibra-dietetica-el-nutriente-clave-para-frenar-la-obesidad-y-las-enfermedades-cronicas/?utm_source=chatgpt.com (2026)-

https://www.nature.com/articles/s41538-025-00698-z (2026).-

https://f1000research.com/articles/13-396 (2026).-

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Dilpreet Kaur's avatar
Dilpreet Kaur
May 20

Your point about butyrate powering the L-cells that produce GLP-1 really clicked for me — it reframes post-meal hunger as a gut signaling issue, not just a willpower problem. I write about metabolic health and gut health on my Substack too, and this mechanism gets massively underappreciated in most mainstream nutrition content. Do you think increasing fiber variety (rather than just total grams) makes a meaningful difference in L-cell stimulation? I'd love to know if the type of fiber matters as much as the amount when it comes to butyrate production.

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