WEIGHT THRESHOLD AND BLOOD-PRESSURE IN A LEAN BLACK-POPULATION

Hypertension is virtually absent in very lean rural African population s but is becoming more common in higher-weight urban African populatio ns and is very common in predominantly obese Westernized black populat ions. This implies that there is a threshold above which weight is rel ated to blood pressure. We studied urban Nigerian civil servants, a le an population in transition toward a more Westernized lifestyle. Blood pressure, fat-related measurements, fasting insulin, physical activit y, alcohol intake, macronutrient intake, and electrolyte excretion wer e measured in 500 male and 299 female civil servants in Benin City, Ni geria, in 1992. Median body mass index (BMI) was 21.5 kg/m(2) in men a nd 24.0 kg/m(2) in women. Examination of age-adjusted mean blood press ure across quantiles of BMI in men and women suggested a threshold of 21.5 kg/m(2) below which blood pressure was not correlated with BMI. A bove this threshold blood pressure was correlated with BMI. Comparison of groups above and below the lower BMI threshold found that differen ces in blood pressure-BMI covariation were not explained by difference s in alcohol intake, caloric or macronutrient intake, or electrolyte e xcretion. Physical activity was higher in men below the threshold. Fas ting insulin and waist-hip ratio were strongly correlated with BMI eve n in this very lean population but neither was independently related t o blood pressure. We conclude that there is a threshold below which li ttle relationship between blood pressure and weight is observed. Above this threshold even at levels considered lean in US blacks, weight is a major determinant of blood pressure in this population of African b lacks, which shares ancestry with US blacks.