In a randomised, single blind controlled trial, 58 patients with mild essential hypertension were administered either a normal diet with a gradual increase in salt and fatty acid consumption (Group A, 30 cases), or an abrupt increase (Group B, 28 cases) for a period of 24 weeks. Group A patients also did more physical activity from weeks 12-24 of the study. At entry to the study, age, sex, risk factors, previous drug therapy and nutrient intakes were comparable between the 2 groups. Adherence to nutrient intakes and exercise was assessed by questionnaires. After 12 weeks, a comparison of changes in mean blood pressure and blood lipids in groups A and B showed no significant difference. However, group B patients showed a significant increase in mean total cholesterol, diastolic pressure and heart rate compared to initial levels. There were no such changes in group A. After 24 weeks, while salt, fatty acids and cholesterol intakes were similar in both groups, there were significantly higher levels of mean total cholesterol, triglycerides, serum sodium, systolic and diastolic blood pressure, and heart rate in group B compared with group A. This may have been due to exercise or to a gradual rather than abrupt increase in salt and fatty acids consumption allowing the body to adapt. Increased physical activity appears to have a positive influence on adaptation leading to prevention of the adverse effects induced by fatty acids and salt loading.