In March 2019 researchers from Iran published their review of the medical scientific literature to assess the effect of psyllium supplementation on body weight, BMI and waist circumference. A total of 22 studies were included in the review. Results showed that psyllium supplementation did not appear to have any significant effect on body weight, BMI or waist circumference.
Darooghegi Mofrad M et al. The effects of psyllium supplementation on body weight, body mass index and waist circumference in adults: A systematic review and dose-response meta-analysis of randomized controlled trials. Crit Rev Food Sci Nutr. 2019 Mar 18:1-14.