Background Telomere shortening is related to aging and unfavourable health outcomes. Obesity and metabolic diseases are important factors for accelerating aging. This study aimed to find out the association between obesity, metabolic disease, and telomere length in metabolically healthy adults. Methods 237 adults were enrolled with written consents at a health promotion centre of a tertiary hospital from February 2014 to March 2015. After excluding 99 subjects who met the exclusion criterion, a total of 130 metabolically healthy subjects were selected for final analysis. The subjects were divided into quartile groups according to the telomere lengths of their oral mucosal cells. Results The subjects consisted of 66 (50.8%) males with a mean age of 58.59 years. The body mass index (BMI, kg/m2) increased significantly along with the quartile groups (Q1, 23.00; Q2, 23.96; Q3, 23.70; Q4, 25.20; P-for trend=0.008). Waist circumference (WC, P-for trend=0.022), waist-to-hip ratio (WHR, P-for trend=0.005), and waist-to-height ratio (WHtR, P=0.001) also increased along with the quartile groups. Obesity prevalence (BMI ≥25 kg/m2), abdominal obesity (WC ≥90 cm for men, ≥85 cm for women), WHR 〉1.0 for men or 〉0.85 for women, and WHtR ≥0.5 increased significantly as the telomere length increased (P-for trend <0.05). After adjusting for covariates, the ORs for each obesity markers increased as the telomere length increased (P-for trend <0.05); and the ORs of WHtR were especially meaningful (Q1, 1.00; Q2, 2.53; Q3, 2.97; Q4, 7.81; P-for trend = 0.001). There were no significant trends for metabolic syndrome and its components along with the prevalence of fatty liver disease. Conclusion Obesity markers and telomere length had significant positive correlation despite the established theory. The obesity paradox may exist in metabolically healthy adults with regard to telomere length, However, further studies with larger sample sizes for the association between obesity and telomere length are needed.