Fibre refers to carbohydrates that humans are unable to digest, and is split into either soluble or insoluble fibre, depending on how they react with liquids.
Insoluble fibres are basically just ‘bulking’ agents that have almost no impact on the body, but soluble fibre can be very beneficial for metabolic health. [191] There are number of studies that demonstrate that soluble fibre can help weight loss, but this fibre must have certain properties.
Fibre fuels healthy bacteria
Scientists estimate that there are around 100 trillion bacteria living in the human gut, with most of this located in the large intestine. [192] These bacteria are referred to as the ‘gut flora’, and while having bacteria in your guy may sound unpleasant, it’s actually a good thing.
Bacteria are crucial for health, with them affecting brain function, blood sugar and weight management. [193]
As living organisms, bacteria need to eat to survive; this is where fibre has its purpose, because it feeds the bacteria which turn it into usable energy.
Gut bacteria produce nutrients that your body needs, such as short-chain fatty acids that are required by cells in the colon. This reduces the level of gut inflammation, and is related to improvements in inflammatory disorders. [194]
Acute or short-term inflammation is good for the body as it enables it to repair damaged cells, but long-term inflammation can be a problem if it starts attacking your body’s tissues.
Low-level, chronic inflammation is now known to be a major feature in almost every long-term disease, such as Alzheimer’s and heart disease. [195]
It is also becoming increasingly apparent that inflammation features strongly in obesity and weight gain, potentially as it affects the production of certain hormones, including leptin. [196]
Numerous studies have found that a high fibre intake tends to lead to lower levels of inflammation, and as such will help with weight management. [197]
Viscous fibres can reduce appetite
Simply put, to lose weight you need to be in a calorie deficit, so you need to burn more calories than you consume. Therefore, anything that reduces hunger levels makes it much easier to take in fewer calories without having to feel starved.
It has been widely thought that fibre is able to make a person feel full, making them more likely to consume less food. However, recent studies suggest that this is not necessarily the case.
A review of 44 studies found that 39 per cent of people taking part in the studies had increased satiety levels while consuming more fibre, but only 22 per cent actually consumed fewer calories.
When broken down even further, it seems that the viscosity of the fibre consumed has a major impact on appetite, with thicker fibres reducing hunger by a larger amount.
Viscous soluble fibres such as psyllium and pectin thicken in water, creating a dense gel-like substance in the gut. This substance slows down the digestion of food and leads to a reduced appetite. [198]
Do fibre supplements work?
Usually, fibre supplements are produced by taking fibre from plants. However, while there may be some health benefits attached to these supplements, there remains a lack of convincing evidence that they positively affect weight loss.
A review study found that guar gum and psyllium, both of which are viscous, soluble fibres, are not effective as a means of aiding weight loss. [199]
The main exception to this lack of evidence is glucomannan, which comes from the konjac root, and has been proven to cause a small amount of weight loss when used as a supplement. [200]
However, in reality the largest benefits come from nutrients working together in the body, and consuming them in isolation will not have the same effects. As a result of this, it is still recommended that you receive your fibre by eating whole plant foods.
Good sources of viscous fibres
Viscous fibres are located almost solely in plant foods such as legumes, asparagus and Brussels sprouts.
When planning to increase your fibre intake by a considerable amount, it is recommended that you do so gradually, as there are a number of negative side effects caused by a rapid increase in fibre intake.
Adding foods rich in viscous, soluble fibre may help you to lose weight, but they will not do so in isolation.
For the most effective results you may need to undergo a lifestyle change, with an increased fibre intake being just a small part of this.
It’s also important to remember that losing weight should not be the only consideration, you are also looking to ensure your mind and body are healthy.
