CLA, chitosan, glucomannan, and fructans for weight loss Original paper

A 2020 meta-analysis of randomized controlled trials found little evidence that whole plants or plant extracts could promote weight loss^[1]. Will compounds isolated from plants or animals fare any better?

This was a meta-analysis of 28 double-blind, parallel-group, randomized, placebo-controlled trials of supplements containing isolated organic compounds.

A compound was included in the meta-analyses if at least 4 trials looked at its effects on the body weight of overweight or obese people aged ≥16. Four compounds satisfied this criteria:

• Chitosan (10 trials, 4 of which lasted ≥12 weeks)
• CLA (8 trials, all of which lasted ≥12 weeks)
• Fructans (4 trials, all of which lasted ≥12 weeks)
• Glucomannan (7 trials, 3 of which lasted ≥12 weeks)

Three of the four compounds reduced body weight:

• Chitosan by 1.8 kg (4.0 lb)
• CLA by 1.1 kg (2.4 lb)
• Glucomannan by 1.3 kg (2.9 lb)

More than 80% of the trials were assessed as being of high or unclear risk of bias in 5 of the 7 domains of the risk-of-bias assessment.

Even if we were to ignore the issues relating to the risk of bias, none of the compounds examined had a clinically relevant effect (defined as a weight loss of ≥2.5 kg). Further, the analyses for chitosan, fructans, and glucomannan included trials of multi-ingredient supplements, which raises issues of potential confounding.