en Gastric Bypass Gastric Bypass Review/Systematic Review Review/Systematic Review <strong>Background and aims:</strong> We aimed to summarize earlier studies on the effects of different types of bariatric surgeries on resting metabolic rate (RMR), resting energy expenditure (REE), and basal metabolic rate (BMR). The aim of this study was to determine the effects of bariatric surgery on the pulmonary function in the morbid obese patients.<br> <strong>Methods:</strong> We searched PubMed, SCOPUS, Web of Science, and Cochrane from inception to October 2020 using relevant keywords. &nbsp;&nbsp;<br> <strong>Results: </strong>Overall 13 studies were included. Pooled effect size suggested a significant effect of bariatric surgeries on REE (Weighted mean difference (WMD): -360.11, 95% CI: -446.67, -273.55, p < 0.0001; I2 = 69.6%), RMR (WMD: -228.05, 95% CI: -290.70, -165.41, p < 0.0001; I2 = 0%), and BMR (WMD: -551.59 mg/dl, 95% CI: -696.25, -406.92, p < 0.0001; I2 = 5.9%).<br> <strong>Conclusion:</strong> Taken together, the data suggest that bariatric surgeries have beneficial effects to reduce REE, RMR, and BMR. Bariatric surgeries, Metabolic rate, Obesity 26 35 http://annbsurg.iums.ac.ir/browse.php?a_code=A-10-53-1&slc_lang=en&sid=1 Ali Sheikhi whitepearl632@yahoo.com 10031947532846001459 10031947532846001459 No Elnaz Daneshzad Daneshzad@gmail.com 10031947532846001460 10031947532846001460 No Moein Askarpour Askarpour@yahoo.com 10031947532846001461 10031947532846001461 No Ehsan Ghaedi Ghaeddi_E@yahoo.com 10031947532846001462 10031947532846001462 No Bagher Larijani Larijanib@yahoo.com 10031947532846001463 10031947532846001463 No Leila Azadbakht Azadbakhtleila@gmail.com 10031947532846001464 10031947532846001464 Yes