Aaron Miller and Chad Jensen, Department of Psychology

Leptin and ghrelin are two hormones involved with suppressing satiety and meal initiation. The primary aim of this study was to evaluate the effects of acute exercise duration of 30 and 60 minutes on the total levels of leptin and ghrelin.

This study was carried out in Provo, Utah. Participants were recruited through flyers in public locations throughout the community, including local high schools. Participants were between the ages of 12-18 years old and in the BMI percentile range of 5th-85th. Participants were randomly assigned to the 30 or 60 minute exercise group, with the opposite protocol being completed one month later. After each bout of exercise, participants provided a saliva sample. These samples were intended for the withinsubjects analysis we would later complete. Saliva samples were prepared with leptin and ghrelin protease inhibitors and stored at -80 ºC. The protease inhibitors prevented the denaturing of our hormones of interest, enabling all saliva samples to be analyzed simultaneously at a future time. The analyses were completed using MAGPIX magnetic bead technology. This technique binds magnetic beads to our hormones of interest. The 96-well trays with our saliva samples were then put into the MAGPIX for reading.

The results from our saliva samples showed the presence of leptin and ghrelin. The kits we used were not sensitive enough to quantify the specific amounts of the individual hormones. This was quite discouraging at first, because of all the work put into this project. Not all researchers have success on their very first try researching a particular topic, and we fall into the same shoes as those researchers. It has been an educational experience to complete this study, regardless of the results we have found. This small setback will not alter out ambition to continue research the effects of exercise duration on appetite hormones. There is still work for us to do to properly quantify leptin and ghrelin. We will be going back to the drawing board to collaborate with other researchers and identify techniques that will be sufficient for salivary hormone analyses. If our hypotheses are correct, the findings can elucidate the effect of exercise duration on the secretion of appetite hormones, as well as highlight the underlying physiological mechanisms that influence dietary behaviors associated with obesity. With obesity on the rise, this research is vital. We will continue to pursue all possibilities to complete this research.