Background: Several studies have revealed that the Masai, pastoralists in Tanzania, have low rates of coronary heart disease despite a diet high in saturated fat. It has also been suggested that they may be genetically protected. Recent studies detailing other potential protective factors, however, are lacking. Methods: A cross-sectional investigation of 985 Tanzanian men and women (130 Masai, 371 rural Bantu and 484 urban Bantu) with mean age of 46 (9.3) years. Anthropometric measures, blood pressure, serum lipids, and the reported dietary pattern and physical activity level were assessed. Results: 82% of Masai subjects reported a high fat/low carbohydrate intake, whereas 77% of the rural Bantu subjects reported a low fat/high carbohydrate intake, while a high fat/high carbohydrate intake was the main dietary pattern of the urban Bantu group as, reported by 55%. The most conspicuous finding for the Masai was the extremely high energy expenditure, corresponding to 2565 kcal/day over basal requirements, compared with 1500 kcal/day in the rural and 891 kcal/day for the urban Bantu. Mean body mass index among the Masai was lower than the rural and urban Bantu. Mean systolic blood pressure of the Masai was also lower compared with their rural and urban Bantu counterparts. The Masai revealed a favourable lipid profile. Conclusion: The potentially atherogenic diet among the Masai was not reflected in serum lipids and was offset probably by very high energy expenditure levels and low body weight.