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Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet]. York (UK): Centre for Reviews and Dissemination (UK); 1995-.

Database of Abstracts of Reviews of Effects (DARE): Quality-assessed Reviews [Internet].

Chromium picolinate for reducing body weight: a meta-analysis of randomized trials

MH Pittler, C Stevinson, and E Ernst.

Review published: 2003.

CRD summary

This review assessed the effect of chromium picolinate on body weight in obese and non-obese people. The authors concluded that any weight loss was small and of doubtful clinical significance. The use of meta-analysis may not have been appropriate. As noted by the authors, the results were not robust because of the considerable influence of one trial.

Authors' objectives

To assess the effect of chromium picolinate on body weight.

Searching

MEDLINE, EMBASE, the Cochrane Library, AMED and CISCOM were searched from their date of inception to January 2002 for publications in any language. Nine experts and four manufacturers of chromium picolinate were contacted for additional published and unpublished studies. Relevant medical journals, conference proceedings and the authors' own files were handsearched. The reference lists of all identified reports were checked.

Study selection

Study designs of evaluations included in the review

Double-blind, randomised controlled trials (RCTs) were eligible for inclusion. The duration of the included studies ranged from 6 to 14 weeks for those in the meta-analysis, and from 8 to 26 weeks for other studies.

Specific interventions included in the review

Studies that compared monopreparations of chromium picolinate with placebo were eligible for inclusion. Studies that used chromium picolinate as part of a multicomponent intervention were excluded. The included studies used chromium picolinate in daily doses ranging from 188 to 1,000 microg. Cointerventions included weight training, running and advice to maintain usual diet.

Participants included in the review

The inclusion criteria relating to the participants were not specified. The included studies were of volunteers, varsity wrestlers, athletes, students, healthy men, obese diabetic patients and obese patients. The body mass index per treatment group, where reported, ranged from 28.4 to 33.2.

Outcomes assessed in the review

Studies that assessed body weight were eligible for inclusion. The primary outcome in the review was the mean change in body weight compared with baseline. The review also assessed the change in lean body mass and percentage body fat, and adverse effects.

How were decisions on the relevance of primary studies made?

Two reviewers independently selected the studies for inclusion and resolved any disagreements through discussion.

Assessment of study quality

Validity was assessed and scored using the Jadad scale, which considers randomisation, blinding and withdrawals. Two reviewers independently assessed validity and resolved any disagreements through discussion.

Data extraction

Two reviewers independently extracted the data and resolved any disagreements through discussion. The mean difference between treatments, together with the 95% confidence interval (CI), was calculated for each study.

Methods of synthesis

How were the studies combined?

The studies were pooled in meta-analyses using a random-effects model. The studies were weighted using the inverse of the variance, which was imputed where necessary. The pooled weighted mean difference (WMD) and 95% CI between treatments was calculated for change in weight, lean body mass and percentage body fat. Publication bias was assessed using a funnel plot.

How were differences between studies investigated?

Statistical heterogeneity was tested using the chi-squared statistic. To test the robustness of the results, the WMD and 95% CI for change in weight and percentage body fat were recalculated after excluding one RCT that accounted for more than 50% of the overall effect. The WMD and 95% CI for weight change were also calculated separately for those studies that included overweight or obese patients and lasted 6 to 13 weeks. Differences among the studies, with respect to cointerventions, sample size and participant characteristics, were also mentioned in the discussion.

Results of the review

Seventeen RCTs (967 patients randomised) were included. Only ten of these (601 patients randomised) provided sufficient data to be included in the meta-analyses.

The validity scores ranged from 2 to 4 out of a maximum of 5 points.

Weight change.

The meta-analysis showed that chromium picolinate significantly reduced weight compared with placebo; the WMD (489 patients) was 1.1 kg (95% CI: -1.8, -0.4). No significant statistical heterogeneity was found (P=1). The funnel plot was asymmetrical, suggesting the possibility of publication bias. The sensitivity analyses suggested that the results were not robust: after excluding one RCT that accounted for 58% of the overall effect, the difference in weight change between chromium picolinate and placebo was no longer statistically significant; WMD (335 patients) was 0.9 kg (95% CI: -2.0, 0.2).

Other outcomes.

The meta-analysis showed no significant difference in lean body mass between chromium picolinate and placebo; the WMD (416 patients) was 0.4 kg (95% CI: -0.1, 0.8). The meta-analysis showed that chromium picolinate significantly reduced the percentage body fat compared with placebo; the WMD (416 patients) was 1.2% (95% CI: -1.7, -0.6). After excluding one RCT that accounted for 61% of the overall effect, the difference in percentage body fat between treatments was no longer statistically significant; the WMD (262 patients) was 0.8% (95% CI: -1.7, 0.2).

Adverse effects.

Three of the included RCTs assessed adverse effects. None found any adverse effects with chromium picolinate.

Authors' conclusions

Chromium picolinate resulted in only a small weight loss compared with placebo. The authors stated that this increased loss was of doubtful clinical importance and the results were not robust.

CRD commentary

The review question was clear in terms of the study design, intervention and outcomes. The inclusion criteria relating to the participants were not specified, and the participants in the included studies varied considerably. Several relevant sources were searched, the search terms were stated, and attempts were made to locate unpublished studies. Two reviewers independently selected the studies, assessed validity and extracted the data; this reduced the potential for bias and errors. Only double-blind RCTs were included and validity was assessed using established criteria. Some relevant information on the included studies was tabulated.

The data were combined in a meta-analysis and statistical heterogeneity was assessed. Given the differences among the study populations (inclusion of athletes, students, healthy men and overweight patients), a meta-analysis may not have been appropriate. It may have been more appropriate to limit the review to overweight populations who would be the target population for any weight-reducing intervention. A sensitivity analysis was carried out by reanalysing the data after excluding the largest RCT, which may have been more likely to detect a significant effect. The authors correctly advised that the results were not robust in view of the considerable influence of one RCT. They also correctly stated that the results were of doubtful clinical importance.

Implications of the review for practice and research

The authors did not state any implications for practice or further research.

Bibliographic details

Pittler M H, Stevinson C, Ernst E. Chromium picolinate for reducing body weight: a meta-analysis of randomized trials. International Journal of Obesity 2003; 27(4): 522-529. [PubMed: 12664086]

Indexing Status

Subject indexing assigned by NLM

MeSH

Dietary Supplements; Female; Humans; Iron Chelating Agents /therapeutic use; Male; Obesity /drug therapy; Picolinic Acids /therapeutic use; Randomized Controlled Trials as Topic

AccessionNumber

12003000871

Database entry date

31/10/2004

Record Status

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.

CRD has determined that this article meets the DARE scientific quality criteria for a systematic review.

Copyright © 2014 University of York.

PMID: 12664086

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