Over 1½ to 3 hours after ingesting 200-350 mg caffeine, on average, RMR increased 4-11% above baseline in 38 healthy, non-obese men (18-65 years) that had mild to moderate daily caffeine consumption (90-200 mg caffeine/d).(Arcerio, 1995; Collins, 1994, and Koot, 1995).

In 10 lean women ((BMI 19.8±0.9 kg/m²(SD); 40-45 y) residing in Japan with daily mild to moderate coffee- or tea-drinking (50-200 mg caffeine/d), individual 30-minute post-caffeine ingestion (200 mg) RMR increases ranged from 10-23% above baseline (Yoshida, 1994). In age-matched, obese (BMI 30.9±1.5 kg/m² (SD) women, a 30-minute post-caffeine ingestion RMR increase above baseline ranged from 1-25%. Correspondingly, group mean RMR increases were 15% and 14% in lean and obese Japanese women, respectively. In U.S.-residing moderate coffee-drinking women (100-300 mg caffeine/d), RMR increased above baseline over 90 minutes, on average, by 15% in 10 younger (21-31 y) subjects and by 8% in 10 older (50-67 y) subjects after ingesting an approximate 240 mg caffeine dose (Arcerio, 2000). 

In 10 older (50-67 y), moderate coffee-drinking women (100-300 mg caffeine/d) women, a blunted thermic effect of caffeine response when expressed as an absolute change over 90 minutes after ingesting approximately 240 mg caffeine, on average (caffeine dosed based on fat-free mass) compared to 10 younger (21-31 y) subjects. There was a statistically-significant body fat percent difference between younger and older women (23.5±5.1 vs. 31.9±5.8 %; P<0.05) (Arcerio, 2000).

Available evidence does not permit conclusions on a dose-response effect of caffeine.