Chitosan for overweight or obesity.
BACKGROUND
Chitosan, a deacetylated chitin, is a dietary supplement reported to decrease body weight. It is widely available over the counter worldwide and although evaluated in a number of trials its efficacy remains in dispute.


OBJECTIVE
To assess the effects of chitosan as a treatment for overweight and obesity.


METHODS
We searched electronic databases (MEDLINE, EMBASE, BIOSIS, CINAHL, The Cochrane Library), specialised web sites (Controlled Trials, IBIDS, SIGLE, Reuter's Health Service, Natural Alternatives International, Pharmanutrients), bibliographies of relevant journal articles, and contacted relevant authors and manufacturers.


METHODS
Trials were included in the review if they were randomised controlled trials of chitosan for a minimum of four weeks duration in adults who were overweight or obese. Authors of included studies were contacted for additional information where appropriate.


METHODS
Details from eligible trials were extracted independently by two reviewers using a standardised data extraction form. Differences in data extraction were resolved by consensus. Continuous data were expressed as weighted mean differences and standard deviations. The pooled effect size was computed by using the inverse variance weighted method.


RESULTS
Fifteen trials including a total of 1219 participants met the inclusion criteria. No trial to date has measured the effect of chitosan on mortality or morbidity. Analyses indicated that chitosan preparations result in a significantly greater weight loss (weighted mean difference -1.7 kg; 95% confidence interval (CI) -2.1 to -1.3 kg, P < 0.00001), decrease in total cholesterol (-0.2 mmol/L [95% CI -0.3 to -0.1], P < 0.00001), and a decrease in systolic and diastolic blood pressure compared with placebo. There were no clear differences between intervention and control groups in terms of frequency of adverse events or in faecal fat excretion. However, the quality of many studies was sub-optimal and analyses restricted to studies that met allocation concealment criteria, were larger, or of longer duration showed that such trials produced substantially smaller decreases in weight and total cholesterol.


CONCLUSIONS
There is some evidence that chitosan is more effective than placebo in the short-term treatment of overweight and obesity. However, many trials to date have been of poor quality and results have been variable. Results obtained from high quality trials indicate that the effect of chitosan on body weight is minimal and unlikely to be of clinical significance.
Jull
Andrew B
AB
Clinical Trials Research Unit, University of Auckland, Private Bag 92019, Auckland, New Zealand. a.jull@ctru.auckland.ac.nz
Ni Mhurchu
Cliona
C
Bennett
Derrick A
DA
Dunshea-Mooij
Christel Ae
CA
Rodgers
Anthony
A
D000328:Adult; D019440:Anti-Obesity Agents / Q000627:therapeutic use*; D048271:Chitosan / Q000627:therapeutic use*; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D008297:Male; D009765:Obesity / Q000188:drug therapy*; D050177:Overweight / Q000188:drug therapy; D016032:Randomized Controlled Trials as Topic; D015431:Weight Loss
D019440:Anti-Obesity Agents; D048271:Chitosan