Genes May Override Exercise in Cholesterol War
Regardless of Exercise Level, Genes May Determine Effects of High-Fat Diet
July 13, 2005 -- For some people, no matter how much time they spend at the
gym or on the couch, it may have little effect on their cholesterol levels.
A new study of identical twins suggests that genes play a major role on how
sensitive our bodies are to fat in the diet, regardless of physical activity
Researchers say the findings may help explain why some sedentary people can
eat a high-fat diet without suffering the artery-clogging consequences while
others who exercise regularly still suffer from high cholesterol levels.
The risk of heart disease increases with elevated low-density lipoprotein
(LDL) cholesterol levels, and decreases with rising high-density lipoprotein
Eating a healthy, low-fat diet and regular exercise can help the vast
majority of people maintain healthy cholesterol levels. But researchers say
their results show that some people may be born with genes that make them
naturally more sensitive or resistant to dietary cholesterol, whether they're a
couch potato or a marathon runner.
Genes May Determine Cholesterol Levels
In the study, researchers compared the effects of switching between a
high-fat diet and a low-fat diet in a group of 28 male twin pairs in which one
twin was an avid runner and the other was sedentary.
The running twin logged about 40 kilometers more per week than his brother,
if the brother exercised at all.
Each twin followed a high-fat diet in which 40% of the calories came from
fat for six weeks and then switched to a low-fat diet with 20% fat for another
six weeks. Their cholesterol levels were measured after each six-week
The results showed that the twins' cholesterol levels responded very
similarly to the different diets, despite the big difference in their exercise
For example, if one sedentary twin experienced a rise in total or LDL
"bad" cholesterol levels on the high-fat diet, so did his
"running" brother. Similarly, if one active twin saw his LDL
cholesterol decrease on the low-fat diet, so did the couch-potato twin.
But some twins seemed to be born with genes that made them insensitive to
dietary fat and experienced little change in their cholesterol levels on either
"Our results suggest there are genes that strongly influence the
LDL-cholesterol response to diet, even in the presence of large differences in
physical activity," write researcher Paul Williams, of Lawrence Berkeley
National Laboratory, and colleagues in the July issue of the American
Journal of Clinical Nutrition.