The Nutracheck nutrient guide to: fibre

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We often focus heavily on the number of calories in our diets, since that’s key to successful weight loss. But we shouldn’t overlook the importance of the nutrients our bodies need too. After all, the food on our plates contains different nutrients in varying amounts — calories are just the total energy those nutrients provide.

To help you better understand the nutrients in your food and why they matter, we’re creating the ultimate guide series to bust myths and equip you with the nutritional know-how to make informed choices about your diet and health. We've already covered carbohydrates and protein — next up is... fiber!

The basics

Technically, fiber is a type of carbohydrate — but it’s a really important one that many of us don’t get enough of. It also behaves quite differently in the body.

The key difference is that, unlike starch and sugar, we can’t digest fiber. Our bodies don’t produce the enzymes needed to break it down. That’s where our gut bacteria step in. We have up to 10 trillion bacteria living in our gut lining — and fiber is their favorite nutrient!

Dietary fiber is generally categorized as either “soluble” or “insoluble,” although newer classifications consider other traits, like how thick it is or how easily it breaks down. Most plant-based foods contain a mix of both types in varying amounts.

• Soluble fiber includes plant pectin and beta-glucans. It’s mainly found in fruits, oats, seeds, beans, and pulses. This type dissolves in water in the gut to form a gel.
• Insoluble fiber, including cellulose, is found mostly in whole grains and nuts. This type doesn’t mix with water — instead, it pulls water into the large intestine.

Why is fiber so good for us?

High-fiber diets are linked to a range of health benefits. In fact, people who eat a fiber-rich diet are more likely to live longer than those who eat less fiber!

For starters, fiber helps lower cholesterol to healthy levels. The gel formed by soluble fiber in the gut binds to cholesterol, reducing how much is reabsorbed into the bloodstream. High levels of LDL (“bad”) cholesterol can increase your risk of heart disease, so eating a fiber-rich diet is a smart way to support heart health. Beta-glucans — found in oats and barley — are especially known for their cholesterol-lowering effects. So, a cozy bowl of oatmeal in the morning is a great option if you’re watching your cholesterol.

Eating a wide variety of fiber sources improves the diversity of your gut microbiome — meaning more types of beneficial bacteria are at work. When these bacteria break down fiber, they produce key compounds like vitamins, hormones, and short-chain fatty acids. These compounds play roles in reducing inflammation, boosting immune function, supporting skin health, and even improving mental well-being. To learn more about supporting your gut microbiome, check out our blog here.

Fiber also supports healthy digestion and regularity. It adds bulk to stool and improves its consistency, making bathroom trips easier. In fact, diets high in fiber — especially whole grains — lower the risk of bowel cancer. Different types of fiber help with different issues: soluble fiber may ease diarrhea, while insoluble fiber can relieve constipation.

Can fiber aid weight loss?

Yes — it can! Studies show that people who eat more fiber tend to have lower BMIs. But why?

Since we can’t digest fiber, we don’t fully absorb the energy (calories) from it. It’s estimated that we only absorb about 1.5–2 calories per gram of fiber. Because of this, high-fiber foods tend to be lower in calories overall.

Fiber also helps us feel full longer. Foods high in fiber take more chewing, which slows down eating and gives your body time to register fullness. After eating, fiber can delay the absorption of nutrients like fat, which can boost satiety.

As mentioned earlier, when gut bacteria digest fiber, they produce short-chain fatty acids. These play a role in appetite regulation by signaling to the body that it's full — lowering levels of the hunger hormone ghrelin and increasing the “I’m full” hormone leptin. This can help reduce the urge to snack and make it easier to stay within your calorie goals.

How much fiber should I be eating?

In the UK, adults are advised to aim for at least 30g of fiber a day. (In the US, the recommendation is similar — around 25g for women and 38g for men.) This number is a minimum, so more is often better. Our hunter-gatherer ancestors are thought to have eaten up to 150g of fiber daily! We’re not saying you need that much, but hitting the 30g mark can offer big health benefits.

If you have a gastrointestinal condition or your doctor has advised a low-fiber diet, be sure to follow their guidance.

How can I include more fiber in my diet?

Want to boost your fiber intake? Here are some easy tips to get started:

• Swap “white” carbs for whole grain options — like whole wheat bread, brown rice, whole grain pasta, and high-fiber breakfast cereals.
• Add more grains like oats, barley, and quinoa to your meals — they’re all excellent fiber sources.
• Sprinkle nuts and seeds on your food. Chia seeds and flaxseeds are especially good — they’re rich in fiber, protein, and heart-healthy omega-3s!
• Eat more beans and pulses. They’re packed with fiber, low in saturated fat, and super budget-friendly. Add them to meals or choose ready-made products that include them — even baked beans count!
• Keep the skins on fruits and veggies — a lot of the insoluble fiber is stored there.

When increasing fiber, go slow and drink plenty of water. Try adding 3–4g more per day for a week, then another 3–4g the next week, and so on until you reach the 30g target. Pay attention to how you feel — if you notice extra bloating or changes in digestion, slow things down to give your body time to adjust. Fiber is great, but too much too quickly can overwhelm your system.

To see just how big a difference smart swaps can make, check out our bread fiber-o-meter below. Just two slices of the right bread can deliver more than a quarter of your 30g daily goal!