The association between metabolically healthy obesity and risk of cancer: A systematic review and meta-analysis of prospective cohort studies.

The risk of cancer among adults with metabolically healthy obesity (MHO) has not yet been established. We systematically searched from inception to 15 March 2020. We included prospective cohort studies that compared participants with MHO and participants with metabolically healthy non-obesity (MHNO) for incidence of any type of cancer. Benign tumors, cancer mortality or cancer prognosis were not in the scope of our analysis. The Newcastle-Ottawa Scale was used for quality assessment. Ultimately, eight studies with a total of 12 542 390 participants were included. The pooled meta-analysis using random effect model showed participants with MHO demonstrated a significantly increased risk of developing cancer (odds ratio [OR], 1.14; 95% confidence interval [CI], 1.05 to 1.23; and I2 = 39%) than those with MHNO. The subgroup analysis revealed a higher pooled estimate (OR, 1.17; 95% CI, 1.01-1.35; and I2 = 56%) in comparison with metabolically healthy normal weight. No evidence of effect modification by age, sex, ethnicity, smoking, sample size or length of follow-up was found. In conclusion, the present study reports a positive association between MHO and cancer incidence. All individuals with obesity, even in the absence of metabolic dysfunction, should be encouraged to lose weight.

The Association between Metabolically Healthy Obesity, Cardiovascular Disease, and All-Cause Mortality Risk in Asia: A Systematic Review and Meta-Analysis.

We investigated the association among metabolically healthy obesity (MHO), cardiovascular disease (CVD)risk, and all-cause mortality in the Asian population. We searched databases from inception to 16 November, 2019 and pooled data using a random-effects model. Subgroup analysis was conducted according to the following comparison groups: MHNW (without overweight or underweight participants) and MHNO (non-obese, including overweight and underweight participants). Nineteen studies were included. The mean Newcastle-Ottawa Scale score was 7.8. Participants with MHO had a significantly higher CVD risk (odds ratio (OR) = 1.36, 95% confidence interval (CI) = 1.13-1.63) and significantly lower risk of all-cause mortality (OR = 0.88, 95% CI = 0.78-1.00) than the comparison group. Subgroup analyses revealed participants with MHO had a significantly higher CVD risk than MHNW participants (OR = 1.61; 95% CI = 1.24-2.08; I2 = 73%), but there was no significant difference compared with MHNO participants (OR, 1.04; 95% CI, 0.80-1.36; I2 = 68%). Participants with MHO had a significantly lower risk of all-cause mortality (OR = 0.83; 95% CI = 0.78-0.88; I2 = 9%) than MHNO participants, but a borderline significantly higher risk of all-cause mortality than MHNW participants (OR = 1.30; 95% CI = 0.99-1.72; I2 = 0%). The CVD risk and all-cause mortality of the MHO group changed depending on the control group. Thus, future studies should select control groups carefully.