UK-based doctor shares quick cheat sheet to understand how fibre works in your body

Fibre works differently for different body types. Here’s a fibre cheat sheet shared by a UK-based doctor that decodes fibre types in a simple guide.

Fibre is known to improve digestion, regulate blood sugar, and promote satiety. However, it’s not a one-speed mechanism that works for all kinds of it. UK-based expert Dr Karan Rajan, in an Instagram post on April 22, 2026, shares a fibre cheat sheet that categorizes different types of fibre based on their fermentation speed in the body. He mentioned the types of fibres, how quickly they are broken down, and where. Here’s a breakdown of the fibre quality.

Fibre cheat sheet for our body. (Unsplash)

Dr Karan captioned, “Fibre isn’t one-speed. Some plants hit early, others take their time, feeding microbes all along the course. So digestion keeps moving, making for smoother runs from start to finish.”

Fast fermenting fibre

In the category of fast fermenting fibres, Dr Karan mentioned artichokes, apples, onions, garlic, raspberries, ripe bananas, asparagus, and corn husk. He explained that the fibres from these plants ferment quickly and make you feel less heavy. These have low molecular mass and less complex structures, which allow for rapid breakdown. It also reduces gut pH and increases beneficial bacterial populations. These fibre breaks down in the ascending colon, producing significant short-chain fatty acids (SCFAs) and gas. It takes around six to 24 hours for these to ferment in our body. According to the National Library of Medicine, these fibres, often soluble, are ideal for reducing inflammation, enhancing immune function, and boosting nutrient absorption.

Medium fermenting fibre

In this category, Dr Karan mentioned oats, carrots, brown rice, guar bean, and broccoli. According to him, these fibres are fermented in the transverse colon. They give more energy, fewer spikes and crashes, and digestion feels balanced. These break down at a moderate pace, providing a balance of prebiotic benefits for gut bacteria without the rapid gas production often associated with high-fermenting fibres. They are ideal for individuals with sensitive guts or SIBO (Small Intestinal Bacterial Overgrowth), and it also supports colon health.

Medium fermenting fibre breaks down in the transverse colon. (Unsplash)

Slow-fermenting fibre

In the category of slow-fermenting fibre, Dr Karan mentioned cassava, wheat, corn, quinoa, chia seeds, beets, almonds, black beans, and underripe bananas. These fibers are fermented down in the descending colon, reducing symptoms like bloating while providing sustained prebiotic benefits and short-chain fatty acids (SCFAs). They make you feel full for longer and reduce craving. The slow-fermenting fibres have the highest impact on metabolic health. Unlike fast-fermenting fibres, these slow-fermenting fibres produce gas at a steadier, lower rate.

Note to readers: This article is for informational purposes only and not a substitute for professional medical advice. It is based on user-generated content from social media. HT.com has not independently verified the claims and does not endorse them.