Association of serum leptin and ghrelin levels with smoking status on body weight: a systematic review and meta-analysis.

BACKGROUND AND AIMS: Smoking cigarettes is a major global health problem that affects appetite and weight. The aim of this systematic review was to determine how smoking affected plasma leptin and ghrelin levels.

METHODS: A comprehensive search of PubMed, Scopus, Web of Science, and Ovid was conducted using a well-established methodology to gather all related publications.

RESULTS: A total of 40 studies were included in the analysis of 11,336 patients. The overall effect showed a with a mean difference (MD) of -1.92[95%CI; -2.63: -1.20] and p  = 0.00001. Subgroup analysis by study design revealed significant differences as well, but with high heterogeneity within the subgroups ( I 2 of 82.3%). Subgroup by sex showed that there was a significant difference in mean difference between the smoking and non-smoking groups for males (MD = -5.75[95% CI; -8.73: -2.77], p  = 0.0002) but not for females (MD = -3.04[95% CI; -6.6:0.54], p  = 0.10). Healthy, pregnant, diabetic and CVD subgroups found significant differences in the healthy (MD = -1.74[95% CI; -03.13: -0.35], p  = 0.01) and diabetic (MD = -7.69[95% CI, -1.64: -0.73], p  = 0.03). subgroups, but not in the pregnant or cardiovascular disease subgroups. On the other hand, the meta-analysis found no statistically significant difference in Ghrelin serum concentration between smokers and non-smokers (MD = 0.52[95% CI, -0.60:1.63], p  = 0.36) and observed heterogeneity in the studies ( I 2  = 68%).

CONCLUSION: This study demonstrates a correlation between smoking and serum leptin/ghrelin levels, which explains smoking's effect on body weight.

SYSTEMATIC REVIEW REGISTRATION: https://www.crd.york.ac.uk/ prospero/display_record.php, identifier (Record ID=326680).