The research team, led by Dr David Prendergast from the State University of New York at Buffalo in the USA, investigated the effect of decreasing or increasing fat intake on a number of cardiovascular risk factors.

The study involved 11 healthy participants who consumed diets in which either 19% of calories or 50% of calories were derived from fat, for a period of 3 weeks. This was followed by a 1-week washout period when they consumed their habitual, 30% fat diet (control diet).

Writing in the Journal of the American College of Nutrition, the researchers report that participants consuming the 19% fat diet had significantly lower HDL cholesterol levels at the end of the study period than those on the 50% fat diet - HDL cholesterol helps protect against heart disease by carrying cholesterol away from the arteries and back to the liver, where it is passed from the body.

In contrast, altered levels of fat intake - high or low - resulted in no changes in blood levels of low-density lipoprotein cholesterol ("bad" cholesterol), triglycerides (human fat compounds), or other traditional cardiovascular risk factors.

Interestingly, the19% fat diet resulted in an average loss in body weight of 0.6 kg, while the consumption of essential fatty acids, vitamin E, and zinc was improved with the 50% fat diet.

Commenting on the results, Dr Prendergast cautioned that they do not mean that everyone should eat a 50% fat diet. However, he suggests that consuming fat in moderation is the best option, and that obtaining 30 to 35% of total energy from fat would be desirable for most people - a level which is slightly higher than that currently recommended by health officials.

The authors conclude: "A low-fat diet (19%) may not provide sufficient calories, essential fatty acids, and some micronutrients (especially vitamin E and zinc) for healthy untrained individuals.

"Increasing fat intake to 50% calories improved nutritional status, and did not negatively affect certain cardiovascular risk factors."