More energy from fiber

Not everyone gets the same amount of energy from their food. A new study shows: Those with a methane-forming gut microbiome can get more energy from dietary fiber. Methanogenic archaea change the fermentation processes in the gut in such a way that more short-chain fatty acids are produced – a hidden energy boost from microorganisms.

Researchers at Arizona State University analyzed 17 test subjects in a strictly controlled nutritional study.

What was done in the study?

Each person was given two diets: a low-fiber “Western Diet” and a high-fiber “Microbiome-Enhancer Diet”. Energy intake, excretion, intestinal gases and the microbiome were comprehensively measured, including continuous methane monitoring in a whole-room calorimeter.

What was the outcome?

About half of the participants had methanogens, mainly Methanobrevibacter smithii. This group had significantly higher methane and propionate levels in the serum – although the amount of fatty acids in the stool remained the same. Genes and transcripts of the propionate-forming succinate pathway were upregulated, indicating increased microbial energy production.

Remarkably, the effect was only seen on the high-fiber diet. The difference disappeared with a typical Western diet.

What are the effects of methanogens in the gut?

The microbial breakdown of dietary fiber produces hydrogen (H₂) as a by-product of fermentation.

High H₂ partial pressure slows down the fermentation processes because many bacteria are then unable to regenerate their NAD⁺. They virtually “suffocate” on their own electrons.

Methanogens(Methanobrevibacter smithii) use precisely this H₂ to form methane (CH₄):

4 H₂ + CO₂ → CH₄ + 2 H₂O

This lowers the H₂ partial pressure in the intestine and makes fermentation thermodynamically more favorable, allowing the remaining bacteria to ferment further and convert more substrates (dietary fiber).

This H₂ consumption creates an ecological advantage:

• Fiber degraders (e.g. Bacteroides, Roseburia, Prevotella) break down complex carbohydrates into sugars.
• Fermenters convert these into short-chain fatty acids (SCFAs).
• Methanogens keep the process going by eliminating excess H₂.

The whole thing works like a production chain: fiber → sugar → SCFAs + H₂ → CH₄

And because the methanogens reduce the “exhaust gas pressure”, production can continue.

This leads to more SCFAs, especially propionate, which can be used by humans.

What does this mean for your health?

Methanogenesis is not a waste product, but part of a highly efficient microbial network. In combination with fiber degraders(Bacteroides, Bifidobacterium, Prevotella) and propionate producers(Odoribacter, Phascolarctobacterium), a consortium is formed that degrades hydrogen, thermodynamically favors fermentation and thus provides more short-chain fatty acids.

The result: higher “metabolizable energy” for the host, a microbial energy boost, so to speak, which only works if there is enough fibre available.

A guide to personalized medicine

Nutrition & Dietetics

Microbiome analysis could help to decide whether a high-fiber diet actually makes sense or is more likely to lead to weight gain. Specific fiber mixtures could also be selected, as not everyone benefits from the same fibers. Some promote methanogenesis more strongly, others hardly at all.

Probiotics / microbiome modulators

Methanogens could be selected as a therapeutic target:

a) Support for malnutrition, cachexia, malabsorption or premature babies.

b) Steaming with metabolic syndrome or obesity

c) Development of new prebiotic strategies: Fibers that specifically activate methanogen-associated bacteria (e.g. Prevotella copri, Roseburia faecis).

Methanogenic active and inactive microbiomes

A methanogenically active microbiome is not automatically better or worse, but simply functions differently. It stands for an “energy-efficient” metabolism: fiber is fermented more, more propionate enters the bloodstream and the body gains more energy from the same food. This is advantageous when energy is needed – for example in cases of underweight, malnutrition, chronic illness or convalescence. In these cases, a methanogenically active microbiome can help to make better use of nutrients.

However, for people with excess energy or a tendency to gain weight, this efficiency can be detrimental. The same amount of fiber provides more usable calories, and the high-fiber diet perceived as “healthy” can contribute to energy intake without being noticed.

Conversely, a methanogenically inactive microbiome does not mean weakness, but rather a “low-energy” type of fermentation: less energy gain from fiber, but often more satiety and potentially more favorable metabolic profiles in the case of obesity.

Calories” are therefore not a fixed quantity. They are microbiome-dependent

Source:

Dirks B et al., Methanogenesis associated with altered microbial production of short-chain fatty acids and human-host metabolizable energy, The ISME Journal 2025; 19(1): wraf103. https://doi.org/10.1093/ismejo/wraf103