A study of nomadic tribes in Africa suggests that people who combine a diet rich in saturated fat but low in total calories with vigorous exercise may not be damaging their hearts as much as previously believed.

Despite their fatty diets, the Fulani of Nigeria had healthy cholesterol levels. The researchers suggest the finding can be attributed to the population's high activity level, low-calorie intake and lack of smoking.

Researchers took blood samples from 121 Fulani men and women aged 15 to 77 and measured total, LDL ("bad") and HDL ("good") cholesterol, as well as several vitamins, and homocysteine -- a protein associated with heart disease risk. They also assessed the population's nutrient intake.

Overall, men consumed about about 1,670 calories -- and women consumed about 1,485 calories -- of which nearly one-half came from fat. And about half of total fat calories were derived from saturated fat. In the US, individuals are advised to consume no more than 30% of their calories from fat, of which no more than 10% should come from saturated fat.

The dietary protein content of the Fulani was also found to be higher than US-recommended levels. Women derived about 16% and men derived about 20% of their calories from protein. US dietary guidelines advise that no more than 15% of daily calories come from protein.

What's more, the typical Fulani diet contained only one third of the level of folate recommended in the US and lower-than-recommended levels of vitamins C and B-6. These vitamins have been linked to a protective effect on the heart.

Despite all of this, participants' average levels of total cholesterol and HDL cholesterol fell within US recommended levels, while average LDL fell below recommended levels. The average body mass index (BMI), a measure of weight and height, was about 20. A BMI of at least 25 is generally considered to be overweight.

Despite a diet high in saturated fat, Fulani adults have a lipid profile indicative of a low risk of cardiovascular disease. This finding is likely due to their high activity level and their low total energy intake.

It is not clear why a diet rich in fat and saturated fat was not associated with elevated cholesterol and heart disease risk but the authors suggest that an overall low intake of calories and a lifestyle marked by physical activity and no tobacco use mitigates the effects of such a diet.

They also note that most of the current recommendations regarding heart disease risk factors are based on studies conducted in Western nations, where the majority of individuals are relatively sedentary. Studies on populations such as the Fulani are rare.

The researchers conclude that the findings with the Fulani do not support the dogma of the past 50 years that high-fat diets necessarily raise cholesterol concentrations.

American Journal of Clinical Nutrition December 2001;74:730-736