Meena Shah, professor, and Joel Mitchell, emeritus professor in kinesiology for the Harris College of Nursing & Health Sciences, mentored students to examine the role of an evening bout of aerobic exercise on blood lipids and lipoproteins after a high-sugar breakfast the following day in postmenopausal women. The study was performed by graduate students Adam Gloeckner and Sarah Bailey. Other investigators included Beverley Adams-Huet, Andreas Kruetzer, and Drs. Dennis Cheek and Jada Willis. Shah and Mitchell recently shared the reasons for the research, what’s next and more. The study was published in the Journal of Sports Sciences.
Why was it important for you to undertake this research?
We know that postmenopausal women have a higher risk for heart disease than younger women. Menopause is associated with dyslipidemia a risk factor for heart disease. Dyslipidemia is characterized by increased levels of LDL cholesterol or “bad cholesterol” and triglycerides and a reduced level of HDL cholesterol or “good cholesterol”. Both the LDL and HDL particles are also smaller and denser further increasing heart disease risk.
Because of the risk for dyslipidemia with aging, we wanted to know if a single bout of exercise in the evening can improve lipids and lipoproteins after breakfast the following day in postmenopausal women. Only one such study has been performed in postmenopausal women and it did not evaluate all the lipoprotein particles needed for a more comprehensive assessment of heart disease risk.
In your research, you included a high-sugar meal, exercise, and post-prandial lipid and lipoprotein measurements. Can you explain their roles?
We fed the participants a high-sugar meal because high-carbohydrate diets are commonly consumed by Americans including postmenopausal women and cause similar changes in blood lipids and lipoproteins to that seen with menopause.
We wanted to see if a bout of aerobic exercise the evening before would improve lipid and lipoprotein response to a high-sugar meal the following day.
The high-sugar meal was given at breakfast because this type of meal is consumed regularly in the mornings by many older Americans. Exercise was performed in the evening because it was more convenient for our participants.
The blood lipids and lipoproteins were measured in the postprandial (after the high-sugar meal) as well as fasted states. Postprandial measurements are important indicators of heart disease risk in the western population since we eat throughout the day and are in a postprandial state most of the 24 hours.
What was your method for conducting the research?
Each of the 22 participants went through both the exercise and no-exercise phase in a random order separated by at least 7 days. During the exercise phase, the participants performed 60 minutes of supervised brisk walking on a treadmill in the late afternoon/early evening followed by dinner. During the no-exercise phase, the participants remained sedentary but had dinner as in the exercise phase. The participants received a high-sugar breakfast the following morning in both the exercise and no-exercise phase. Blood lipid and lipoproteins were assessed in the fasting state and postprandial state at 60, 120, and 180 minutes after breakfast. Dietary intake and physical activity levels were controlled for 48 hours prior to each phase.
What was the outcome of your study?
Our results showed that just a single bout of exercise performed the evening before lowered postprandial triglycerides and VLDL (a lipoprotein made by the liver that carries triglycerides in the bloodstream) following a high-sugar breakfast the following day in postmenopausal women. These results need to be verified by other similar studies.
What’s next?
Future studies should evaluate the effect of long-term exercise training on postprandial lipid and lipoprotein response to high-carbohydrate meals in postmenopausal women.