Kinesiology research leads to healthy discoveries

Fort Worth, TX

12/11/2008

A single bout of moderate aerobic exercise before eating a meal high in carbohydrates can have triglyceride-lowering effects, even if a young woman is overweight and doesn’t exercise regularly. That, according to a study by TCU kinesiology researchers, also might represent an early glimpse of why there are sustained beneficial effects of lower triglycerides typically found in women who do exercise frequently.

The study, recently published in the Journal of Sport Nutrition and Exercise Metabolism and done with the help of family medicine researchers at John Peter Smith Hospital in Fort Worth, tracked 20 women ages 18-25 and found that exercising for sixty minutes on stationary bikes before eating high-carbohydrate meals lowered the blood lipid levels well known as risk factors for cardiovascular disease. Researchers studied 20 sedentary women with normal weights and 20 women who were sedentary and overweight, and each group showed improvement in its triglyceride level.

If a woman exercises regularly, she often will build up a “training adaptation,” where she has sustained improvement in her metabolic function. While that chronic effect is usually gained slowly over time, the researchers found markers that responded positively with a single effort to exercise, said the study’s lead researcher Dr. Joel Mitchell, professor and chair of TCU’s Department of Kinesiology.

“If you look at general guidelines, low-fat diets and diets low in carbohydrates are recommended, and we all know that regular exercise produces beneficial outcomes,” he said. “What we were looking at was how much of the beneficial effect is due to chronic adaptation and how much is due to ‘the recent effect,’ which can carry forward for 24 or, in some cases, even more hours. The overweight women received benefits from the exercise, as well as improved glucose disposal.

“A lot of the work that’s usually done when studying cardiovascular disease, high triglycerides and the risks of Type II diabetes is done on populations that are older because those are the populations most at risk. However, we wanted to see if these college-age women were going to show early signs of these risks and how well they would respond to exercise. They responded well, even though we thought we might see a differential response based on the presence of the excess weight of some of the women.”

The study represents a small sampling and there are no immediate plans for a follow up study. Mitchell suggested, based on these findings and the work of other researchers, it’s likely that similar results would be present if women of older ages or men were tested. Another study currently being conducted in the kinesiology department and in collaboration with Dr. Dennis Cheek, Abell-Hanger Professor of Gerontological Nursing, is looking at the role of blood vessel function as a cardiovascular risk factor in older women.

Triglycerides are the chemical form in which most fat exists in food, as well as in the body. They’re also present in blood plasma and, in association with cholesterol, form the plasma lipids.

Triglycerides in plasma are derived from fats eaten in foods or made in the body from other energy sources like carbohydrates. Calories ingested in a meal and not used immediately by tissues are converted to triglycerides and transported to fat cells to be stored. Hormones regulate the release of triglycerides from fat tissue so they meet the body’s need for energy between meals.

To lower triglyceride levels and improve overall health, the American Heart Association recommends an individual get at least 30 minutes of moderate-intensity physical activity on five or more days each week and eat more fruits and vegetables, as well as non-fatty fish. People with high triglycerides also may need to substitute monounsaturated and polyunsaturated fats --such as those found in canola oil, olive oil or liquid margarine -- for saturated fats. Substituting carbohydrates for fats may raise triglyceride levels and may decrease HDL (“good”) cholesterol in some people.

“Lipid levels and rates of glucose uptake are markers of tendencies for increased risk of diseases associated with the metabolic syndrome; specifically, cardiovascular disease and Type II diabetes. Findings from studies such as ours should heighten awareness that a lot of people are at risk for problems in the future,” Mitchell said. “These women are young, in their late teens and early 20s, and, even if a woman can get by for a long time as a young individual with reasonably good health despite poor eating habits and being overweight, we know there’s still a high probability that it’s going to catch up with you.”