The role of dietary fibre in weight management has been investigated for many decades and is still debated. A recently published systematic review and meta-analysis of randomised controlled trials sheds more light on the subject by specifically investigating the effect of viscous dietary fibres on body weight, waist circumference, body mass index (BMI), and body fat, independent of energy (kilojoule/calorie) reduction.
Agar, alginate, β-glucan, guar gum, konjac, viscous fiber blend (konjac, alginate, and xanthan), psyllium and xanthan gum are all common kinds of viscous dietary fibres that are found naturally in foods, are added as ingredients, or can be consumed as fibre supplements, and were included in the systematic review.
There was a total of 62 trails including 3,877 people, with an average age of 51 years (range 16 – 70 years), and a baseline body mass index (BMI) of 27 (range 19 - 33) kg/m2. Around one fifth (18%) of participants had diabetes and/or the metabolic syndrome and over a third (37%) were at risk of cardiovascular disease (e.g., heart disease or stroke). The main findings were:
- consuming 8 g (range 0.8 - 36 g) of viscous fibre a day leads to a 0.33 kg decrease in body weight over 8 weeks (range 4-52 weeks), with evidence that the longer people consume the soluble dietary fibre, the more weight they lose.
- consuming 7 g (range 2.3 - 36 g) of viscous fibre a day leads to a 0.63 cm decrease in waist circumference over 12 weeks (range 4-52 weeks), with evidence that the longer people consume the soluble dietary fibre, the smaller their waist circumference.
- consuming 6 g (range 1.3 - 36 g) of viscous fibre a day leads to a 0.28 kg/m2 decrease in BMI over 8 weeks (range 4-52 weeks).
- consuming 9 g (range 3 - 36 g) of viscous fibre a day did not quite lead to a statistically significant decrease (-0.78%, P=0.05) in body fat over 8 weeks (range 4-52 weeks).
While the reductions in weight, BMI and waist circumference are not huge by any measure, they were all independent of energy (kilojoule/calorie) reduction and are comparable to other popular dietary approaches like the Mediterranean-style diet (0.29 kg reduction in body weight), low-carbohydrate diet (0.48 kg reduction in body weight) and high–dietary pulses (legumes) diet (0.34 kg reduction in body weight).
Therefore, making sure you include more soluble dietary fibre in your diet may have some added benefits if you are trying to lose weight or get into shape.
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Alan Barclay, PhD is a consultant dietitian and chef (Cert III). He worked for Diabetes Australia (NSW) from 1998–2014 . He is author/co-author of more than 30 scientific publications, and author/co-author of The good Carbs Cookbook (Murdoch Books), Reversing Diabetes (Murdoch Books), The Low GI Diet: Managing Type 2 Diabetes (Hachette Australia) and The Ultimate Guide to Sugars and Sweeteners (The Experiment, New York).
Contact: You can follow him on Twitter, LinkedIn or check out his website.
