Aims To assess the relationship between oral health status and Body Mass Index. Material and methods This paper relates to the free-living sample (participants who lived in their own home, rather than an institution) of the National Diet and Nutrition Survey: people aged 65 years and older. Subjects 629 adults. Data collection A probability random national sample of adults who had a dental examination, an interview and an anthropometric examination. Data analysis Fisher's exact test and multivariate logistic modeling. Findings Being underweight was relatively uncommon in this population. People without teeth were significantly (P=0.05) more likely to be underweight than those with 11 or more teeth; 12.3% and 2.9%. A highly statistically significant (P=0.001) difference was observed in BMI between dentate people with 1-10 teeth and with more than 10 teeth; 24% and 2.9% were underweight. Dentate people with less than 21 natural teeth were on average more than 3 times more likely to be obese than those with 21-32 teeth (P=0.036). There was no significant difference in both the proportion of overweight and obese adults between those who were edentulous and dentate with 21 or more teeth. A similar pattern was observed when the number of posterior occluding pairs was compared with BMI categories. Results of multiple logistic regression were adjusted for the confounding effects of age, social class, region of origin and partial denture wearing. Conclusions Older people in Britain with more than 20 teeth are more likely to have a normal Body Mass Index.Dental status can affect diet, nutrition and health by changes in the types of food eaten. 1-3 Tooth loss has been associated with changes in food preference and nutritional deficiency. 4 dence that people whose mastication is impaired by tooth loss are more likely to be underweight is conflicting. In the 1967-1968 DHSS 6 study of elderly people in Britain, Berry found that inefficient mastication was associated with being underweight and leanness. They also had 20% less energy intake. Further evidence for an association between edentulousness and under-nutrition comes from the British DHSS survey 6 of nutrition and health in old age. Conversely, differences in body weight by dental status were not found by Elwood and Bates. 7 Halling, Bengtsson and Avridsson, 8 on the other hand, found that body weight was higher in edentulous people and in those with 1-15 teeth compared with those with more than 15 teeth. A similar trend was reported by Nowjack-Raymer 9 in a large national survey in the USA.Overall it appears that edentulousness and chewing problems are related to being underweight, 10-12 but the true relationship is far from clear. Whilst relationships between dental state, chewing ability and food choice have been explored, these studies often suffer from being small scale, non-representative or insufficiently rigorous in the collection of nutritional data. There are only very limited data linking nutrition or general health with dental state. From the point of view b...