Objective: Flaxseed (Linum usitatissimum) supplementation has shown promise as an anti-
obesity agent in various clinical trials, although results have been inconsistent. To provide a
more accurate assessment of the impact of flaxseed supplementation on anthropometric
indices, a systematic review and meta-analysis was performed. Methods: We searched several
international databases until August 2023, including Scopus, PubMed, Web of Science,
Embase, and Cochrane Library. Weighted mean differences (WMDs) were analyzed using a
random-effects model. Results: Sixty-four trials comprising 72 treatment arms were included. All
studies reported the intervention types (Lignans, Whole flaxseed, and Flaxseed oil) and dosage.
However, three studies did testing for purity, and 40 studies reported potency. Also, the risk of
contamination with heavy metals was not mentioned in studies. Another limitation was the lack
of blind evaluation in the studies. According to three trials included in the systematic review,
flaxseed did not affect anthropometric indices. Our meta-analysis revealed significant reductions
in body weight (WMD = −0.63 kg; 95 % CI: −1.00, −0.27, P < 0.001; I 2 = 76.7 %,
P < 0.001), body mass index (BMI) (WMD: −0.24 kg/m2, 95 % CI: −0.36, −0.11, P < 0.001; I 2 =
78.5 %, P < 0.001) and waist circumference (WC) (WMD: −1.43 cm, 95 % CI: −2.06, −0.80,
P < 0.001; I 2 = 81.1 %, P < 0.001) following flaxseed supplementation. Subgroup analyses
indicated that interventions lasting 10–20 weeks, and studies involving subjects with higher BMI
(>30 kg/m 2 ) showed more significant anti-obesity effects. Based on the GRADE evaluation, body
weight, BMI, and WC results were considered as moderate-certainty evidence. Conclusion: Our
systematic review and meta-analysis suggests that supplementation with flaxseed (Linum
usitatissimum) leads to meaningful improvements in body weight, BMI, and WC. Therefore,
flaxseed can be considered as an adjunctive therapeutic approach in improving obesity.
Complement Ther Med., 2024, Jul 9;84:103066. doi: 10.1016/j.ctim.2024.103066