We did not find any paper that assessed clinical inertia in obese patients. Therefore, no paper has compared the clinical inertia rates between morbidly and nonmorbidly obese patients. A cross-sectional observational study was carried out. We analysed 8687 obese patients ⩾40 years of age who attended their health-care center for a checkup as part of a preventive program. The outcome was morbid obesity. Secondary variables were as follows: failure in the management of high blood pressure (HBP), high blood cholesterol (HBC) and high fasting blood glucose (HFBG); gender; personal history of hypertension, dyslipidemia, diabetes, smoking and cardiovascular disease; and age (years). We analysed the association between failures and morbid obesity by calculating the adjusted odds ratio (OR). Of 8687 obese patients, 421 had morbid obesity (4.8%, 95% confidence interval (CI): 4.4-5.3%). The prevalence rates for failures were as follows: HBP, 34.7%; HBC, 35.2%; and HFBG, 12.4%. Associated factors with morbid obesity related with failures were as follows: failure in the management of HBP (OR=1.42, 95% CI: 1.15-1.74, P=0.001); failure in the management of HBC (OR=0.73, 95% CI: 0.58-0.91, P=0.004); and failure in the management of HFBG (OR=2.24, 95% CI: 1.66-3.03, P<0.001). Morbidly obese patients faced worse management for HBP and HFBG, and better management for HBC. It would be interesting to integrate alarm systems to avoid this problem.