Why fibre is the next big thing in sports nutrition

When it comes to sports nutrition, many of us think of protein shakes and energy gels. But what if I told you that fibre is also a superfood for sport and exercise?  

Dietary fibre is a type of carbohydrate found in plant-based foods like vegetables, fruits, legumes, nuts, seeds, and grains. Fibre is best known for its ability to promote gut health and "keep us regular". But fibre is so much more than that, with properties that support weight loss, energy levels, muscle growth, and endurance exercise. Here’s what you need to know.

Weight Loss

Fibre absorbs water and creates bulk in the stomach. This bulk delays gastric emptying and helps you feel full for longer. Foods high in fibre are usually lower in calories too. One study showed that people who increased their dietary fibre lost more weight and were able to more effectively adhere to their daily energy (calorie) recommendations. 

Our gut microbiome (the trillions of beneficial microorganisms) can also assist in weight management. Fibre promotes the growth and diversity of specific gut bacteria – including Prevotella and Faecalibacterium prausnitzii. These bacteria are known to play a role in weight management, and blood sugar control, achieved by producing anti-inflammatory substances called Short Chain Fatty Acids (SCFAs). SCFAs bind to receptors that stimulate the production of gut hormones that suppress appetite. SCFAs also reduce systemic inflammation which is a key driver of insulin resistance and fat production (lipogenesis).

Energy levels

Due to its bulking properties, fibre slows the absorption of sugar into the bloodstream, and prevents blood sugar “spikes”. This helps to achieve more consistent energy levels across the day, reduces mid-afternoon sugar cravings, and provides sufficient energy for afternoon/evening workouts.

Muscle growth

Fibre slows the digestive process, and allows the body more time to absorb important nutrients for muscle synthesis, like protein. Fibre, by producing SCFAS, also assists in the absorption of key vitamins and minerals by supporting a healthy gut lining. For muscle growth, it’s important not to consume a lot of fibre straight after your workout. At this point, you need easily accessed fuel (carbohydrates and protein) to assist in recovery and maximise strength gains.   

Endurance exercise

There is some fascinating research emerging supporting the role of fibre in endurance exercise. These effects are largely achieved when fibre is fermented by our gut bacteria to produce SCFAs, including butyrate and propionate.

A study published in Nature Medicine showed that after running the Boston Marathon, the abundance of Veillonella microbes increased. What's so important about Veillonella you say? Well, it's a microbe that consumes lactate and converts it into propionate. Propionate was then directly linked to enhanced athletic performance, which was replicated using a treadmill performance task. 

Secondly, the SCFA butyrate may indirectly enhance exercise performance by regulating systemic levels of inflammation and boosting immune function. Supporting immune health is critical to an athlete's ability to maintain a heavy training schedule and recover quickly.

Like with muscle growth, the timing of fibre intake is important. As fibre slows digestion, it's not ideal to consume just before a training session or competition. This is when you need fast-acting energy to fuel performance. Fibre might also contribute to adverse gastrointestinal symptoms, like diarrhoea. Instead, it is best to consume high-fibre foods throughout the day, ideally more than two hours before a hard workout.

Bottom line

Aim for >30g dietary fibre spread throughout the day, but ideally no more than two hours before or after a hard workout.