Abstract Background: The prevalence of obesity and Metabolic syndrome (MetS) in the general population has been documented extensively. While obesity and MetS are associated with cancer risk and may persist after diagnosis, the prevalence and the secular trends of obesity and MetS among cancer survivors has not been examined in a nationally representative cohort. Objective: To compare adults diagnosed with cancer and those without cancer on the prevalence of obesity and MetS in 2013-2014, and on the time trends over the past years from 1999 through 2014. Methods: A sample of 39,608 adults, aged 20+ who participated in National Health and Nutrition Examination Survey (NHANES) surveys from 1999-2014 were included. Of those surveyed, 2,811 subjects had been diagnosed with non-skin cancers, and 1,770 with obesity-linked cancers (colorectal, liver, kidney, esophageal, stomach, pancreatic, gallbladder, breast, endometrial, ovarian and prostate). MetS was defined as having at least three of the following five factors: elevated levels of (1) triglyceride, (2) systolic or diastolic blood pressure, or use of anti-hypertensive medication, (3) blood glucose or self-reported diabetes or use of insulin, (4) enlarged waist circumference and (5) lower levels of high-density lipoprotein (HDL) cholesterol or use of cholesterol lowering medication. Results: In 2013-2014, the prevalence of obesity was 41.1%, 40.5% and 37.8% among adults diagnosed with obesity-linked cancers, total-cancer, and no cancer diagnosis, respectively. The prevalence of obesity have significantly increased over the last 16 years for all three groups. Relative to adults without a cancer diagnosis, the 16-year increase in obesity prevalence was significantly higher for those with obesity-linked cancers (p=0.019), but not with total cancer (p=0.35). In relation to MetS, the 2013-2014 prevalence was significantly higher among adults with obesity-linked cancers (52.7%) and total cancer (50.3%) compared to adults without cancer (29.2%). Over the 16-year period from 1999-2014, the prevalence of MetS has increased among adults with obesity-linked cancers (p=0.008), total cancer (p=<.0001), and those without a cancer diagnosis (p=0.005), respectively. Compared to the adults without a cancer diagnosis, the prevalence of MetS over the years has significantly increased among adults with obesity-linked cancers (p=0.004) and total cancer (p=0.05) were significantly higher. Conclusion: U.S. adults diagnosed with obesity-linked cancers had a higher prevalence of obesity and MetS, and the prevalence have significantly increased over the last 16 years, compared to those without a cancer diagnosis. The findings of this study underscore the urgent need for clinicians and public health workers to recognize and address cardiometabolic health problems among cancer survivors. Citation Format: Wambui Grace Gathirua-Mwangi. Prevalence and trends of obesity and metabolic syndrome among U.S. adults diagnosed with cancer, NHANES 1999-2014 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5257.