"Both consuming plant sterols and exercising have been shown to affect blood cholesterol levels on their own," said lead researcher Professor Peter Jones from McGill University in Montreal, Canada. "Our research is the first to look at the complementary combined effects of these therapies."

For their study, the researchers recruited 74 non-active volunteers between the ages of 40 and 70 years. The participants were divided into four groups: combination (consumed margarine containing plant sterols and exercised), exercise (consumed margarine free of plant-sterols and exercised), sterol only (consumed margarine containing plant sterols and did not exercise) and control (consumed plant-sterol free margarine and did not exercise). The exercise regime consisted of stair stepping and cycling three times a week, while the margarine was consumed four times a day.

Levels of fats (lipids) in the participants' blood, such as low-density lipoprotein (LDL) cholesterol, known as "bad" cholesterol, high-density lipoprotein (HDL) cholesterol, known as "good" cholesterol, and triacylglycerol were measured at both the beginning and end of the 8-week study period.

The researchers found that, in comparison with plant sterols or exercise alone, the combination of both produced the most beneficial change in the participants' blood-fat levels.

"This combination therapy favourably altered their lipid profiles by decreasing total cholesterol, LDL cholesterol, and triacylglycerol levels and by increasing HDL cholesterol levels," said researcher Krista Varady, also from McGill University. "Our volunteers were typically inactive. In addition to the altered cholesterol levels, the increased physical activity contributed to loss of weight and improved motivation."

Writing in the American Journal of Clinical Nutrition, the researchers conclude: "These findings suggest that combination therapy may improve the cholesterol and lipid levels in previously sedentary adults who have high cholesterol. Furthermore, this therapy may reduce the risk of coronary artery disease for these individuals."