Caffeine in the form of tea and coffee is the most widely consumed, socially acceptable stimulant around the globe. More than 150 million people in the United States drink coffee daily, with an average intake of 2 cups (which contains about 280 mg of caffeine).
Caffeine results in the release of excitatory neurotransmitters. Caffeine may increase energy expenditure and has been associated with reduced body mass. Studies have observed lower body mass index (BMI) in coffee consumers, compared with individuals who don’t consume coffee. Coffee may reduce appetite and dietary intake.
Greek researchers at Harokopio University, Athens, conducted a cross-over study to evaluate the effects of caffeinated coffee on appetite and dietary intake (Obesity 2013;21:1127-32). Sixteen normal-weight and 17 overweight/obese habitual coffee consumers (at least 1 cup of coffee/day) were enrolled. Each participant took part in three trials at least 1 week apart. Participants were required to abstain from caffeine for 24 hours and then reported to the lab to consume a breakfast and 200 mL of one of three experimental beverages: instant coffee with 3 mg caffeine/kg body weight (Coffee 3); instant coffee with 6 mg caffeine/kg (Coffee 6); or water. Participants had to consume the breakfast and the beverage within 5 minutes.
During a 3-hour period following beverage consumption, appetite feelings and participants’ dietary intake the day before the experiment were assessed. After this 3-hour period, participants were offered an ad libitum lunch buffet. The following day, participants reported by telephone their food and fluid intake for the rest of the experiment day.
Normal-weight participants consumed comparable energy in the ad libitum meal and in their total daily intake in the three interventions. However, among overweight/obese individuals, Coffee 6 resulted in significantly reduced energy intake during the ad libitum meal, compared with Coffee 3, and in significantly reduced total day energy intake, compared with both water and Coffee 3.
Doses used in this study for participants were somewhat staggering. The average caffeine content of the beverage in the Coffee 6 group was 526 mg. This is the caffeine content of roughly four 8-ounce cups of brewed coffee. The authors acknowledged that the Coffee 6 beverage was not easily consumed by "most of the volunteers."
We need to be cautious about the use of this dosing in the clinical setting. But as part of comprehensive weight-management strategy, caffeinated coffee may be helpful for reducing energy intake.
Dr. Ebbert is professor of medicine, a general internist at the Mayo Clinic in Rochester, Minn., and a diplomate of the American Board of Addiction Medicine. The opinions expressed are those of the author. He reports no conflicts of interest.