OBJECTIVE To quantify the impact of obesity on the number of visits to both primary and secondary care teams. METHODS The adult populations of 80 general practices throughout the United Kingdom were classified according to their BMI. We undertook a cross-sectional survey of computer-generated and handwritten records of 6150 obese people (BMI > or = 30 kg/m(2)) and 1150 normal weight (BMI = 18.5 to 24.9 kg/m(2)) control subjects over an 18-month retrospective period. RESULTS Obese patients made significantly more visits to the general practitioner (GP), practice nurse (PN), and hospital outpatient units than normal weight patients (all p < 0.001), and they were admitted to the hospital more often (p = 0.034). For both GP and PN visits, the relationship remained after adjusting for age, sex, social deprivation category, country, and number of comorbidities. Among obese patients, there was an increasing relationship between frequent GP visits (at least four appointments) and greater BMI, which remained significant after adjustment had been made for age, sex, deprivation, country, and number of comorbidities. CONCLUSIONS The human resource burden to general practice is significantly higher in the obese population than in the normal weight population, even when adjusted for confounding factors. The increase in prevalence of obesity will continue to put pressure on GP and PN time unless appropriate action is taken.