After researchers took baseline heart rate and blood pressure, participants drank a beverage containing 50 mg, 100 mg or 200 mg of caffeine, or one with no caffeine that served as a placebo. The order was randomized across the four visits for each participant.
Blood pressure and heart rate measurements were taken every 10 minutes during the first hour. The teens completed the behavioral checklist again and munched on snack food. After the fourth session, participants had their height and weight measured, and were debriefed about the study.
In addition to the general findings, the study revealed several differences in response to caffeine between girls and boys. Diastolic blood pressure increased and heart rate decreased as percentage of caffeine increased in males, but not in females. In addition, boys who were regular "high consumers" of caffeine showed greater increases in blood pressure than low-consuming boys.
"Caffeine is known to increase blood pressure, but the fact that it caused an exaggerated response in high-consuming males was a surprise, since at the time of measurement the amount of caffeine consumed by boys and girls was the same," says Temple.
"We would have predicted that high consumers would have developed some tolerance to the effects of caffeine and would have reduced responses."
When researchers examined eating behavior as a function of chronic and acute caffeine use, they found that high consumers of caffeine consumed more calories, protein and fat in their typical diet, and ate more high-sugar snack foods in the laboratory, compared with low-caffeine consumers.
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|Contact: Lois Baker|
University at Buffalo