Journal Title (Medline/Pubmed accepted abbreviation): Nutr. & Metab.
First page: 66
Background: Exercise affects glucose and insulin concentrations in the blood because of increased energy demands. In addition, exercise affects neural signals from the sympathetic and/or parasympathetic nervous system, which can affect hormone release and response.
A relatively new subcutaneous (under the skin) device called the continuous glucose monitoring system has been developed that can continuously monitor blood glucose for long periods of time (in this experiment, 3 days). Also in this study, the investigators continuously monitored heart rate during the day and were able to examine the cardiogram for activity of the autonomic nervous system.
Hypothesis: Exercise will alter activity of the autonomic nervous system, altering communication between the gut and the brain and thereby delaying the hunger response after exercise if exercise is done before the meal.
Subjects: Nine healthy males, age 21.9 ± 1.8 yrs old
Experimental design: randomized, cross-over
Conditions: mid-morning exercise or rest
Protocol : On day 0, the glucose monitoring system was inserted into the participant’s lateral abdominal wall. Test days were days 1 and 3. On these days, they reported to the laboratory after an overnight fast. They ate a standard breakfast at 8:30am. At 10:15 am, they rested or exercised (stationary bicycle at 70% of their previously determined VO 2max). Lunch (the same amount on day 3 as was consumed on day 1) was given when they requested it. During lunch, blood glucose and gas exchange were monitored. The glucose monitoring system was removed after the last gas exchange measurement on day 3. Hunger/satiation questionnaires were completed throughout the morning until lunch commenced.
Exercise did not change timing of hunger for lunch in these participants, but it significantly changed the mobilization of fat and the blood glucose response to a meal. The mechanisms by which exercise prevents and helps control diabetes are still being understood.