Overweight and Obesity: Findings from 20 Years of the Tehran Lipid and Glucose Study

CONTEXT: The prevalence of overweight and obesity are increasing worldwide and have frequently been associated with health risks. This review highlighted several studies regarding obesity, outlining contributions of over a span of almost two decades in the Tehran Lipid and Glucose Study (TLGS). EVIDENCE ACQUISITION: A systematic review was undertaken to retrieve articles related to all aspects of obesity from the earliest available date up to January 30, 2017. RESULTS: Prevalence of excess weight, including overweight and obesity were 20.8 and 63.6% among those aged below and above 20 years, respectively. TLGS found a high incidence of obesity with higher incidence in women among Tehranian adults; the cumulative incidence of obesity was 31.3, 38.1 and 23.4% for the whole population, women, and men, respectively. In children and adolescents, younger non-obese 7 - 9 years old, compared to 10 - 11 year olds are at greater risk of obesity. Prevalences of abdominal obesity in men and women were 52.8% and 44.4% respectively. Similar to generalized obesity, a high incidence of abdominal obesity was observed; the total cumulative incidence of abdominal obesity was 76.0% (83.6% for men and 70.9% for women). Metabolically healthy obese (MHO) and metabolically healthy abdominal obese (MHAO) are two important obesity phenotypes. People with these phenotypes have different risks for cardiovascular disease (CVD), type 2 diabetes (T2DM), and mortality. In the TLGS participants, MHO was found in 2% and 7.7% of the whole and obese population, respectively, whereas MHAO phenotype was reported in 12.4% and 23.5% of the whole and abdominal obese population. In these unstable conditions, during the long term follow up the metabolic risks developed in nearly half of the individuals. During a 12-year follow-up, incident CVD did not increase in the MHO phenotype compared to metabolically healthy normal weight (MHNW) individuals, but the risk of CVD events had increased in all metabolically unhealthy phenotypes. However in another report, over a 10-year follow-up, MHAO phenotype had an increased risk for CVD in comparison to the reference group, metabolically healthy non-abdominal obese (MHNAO) individuals. CONCLUSIONS: The TLGS studies bridged the significant gap in knowledge regarding prevalence, incidence, trends, morbidities and mortalities for obesity among Iranian population.