Association between obesity and calcium:phosphorus ratio in the habitual diets of adults in a city of Northeastern Brazil: an epidemiological study

BACKGROUND Low calcium:phosphorus ratios (Ca:P ratio) in habitual diet have been observed worldwide, and it has been shown to be harmful to the bone health of the population. However, no study associating this ratio with obesity was found. Thus, considering that the intake of calcium and phosphorus will generate a ratio between them, which may be associated with obesity, this research seeks at evaluating the relation between obesity and the Ca:P ratio in the habitual diet of adults. METHODS Cross-sectional population-based epidemiological study with stratified and systematic sampling. The sample was composed of 506 adults, aged between 18 and 60 years, of both genders. Information on socioeconomic and demographic conditions was obtained through questionnaires completed during home visits, where anthropometric and dietary evaluations were also conducted. RESULTS In the habitual diet consumed by the study subjects, a Ca:P ratio above the median of 0.57 reduced the risk of central obesity based on waist-to-height ratio (WHtR) (OR: 0.61; 95% CI: 0.41 - 0.92). Habitual dietary intake of calcium (OR: 0.65; 95% CI: 0.43 - 0.97) and dairy products (OR: 0.56; 95% CI: 0.37 - 0.84) above the median value (485.4 mg and 0.9 servings, respectively) was found to be a protective factor related to central obesity based on WHtR. CONCLUSIONS Values above the median for the Ca:P ratio found in the habitual diet were negatively associated with central obesity based on WHtR. In addition, calcium and dairy consumption were negatively associated with central obesity based on WHtR. Therefore, higher Ca:P ratios contributed to a lower prevalence of central obesity.