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Caffeine Clinical Studies
Caffeine and coffee: their influence on metabolic rate and substrate utilization in normal weight and obese individuals
"Thus in conclusion it would seem that the consumption of caffeine or coffee, in reasonable quantities, would be a supplementary advantage to those following a weight reducing regime. However, if our short-term results are extrapolated, the effect of caffeine on normal, slightly overweight individuals would be a loss of weight due to an increased energy expenditure associated with a change in body composition, i.e., a decrease in fat stores, whereas the obese would lose body energy due to an increased metabolic rate with less mobilization and utilization of their fat stores."
[K. J. Acheson PhD, Caffeine and coffee: their influence on metabolic rate and substrate utilization in normal weight and obese individuals, The American Journal of Clinical Nutrition (1980), 33:989-997.]
Caffeine: a double-blind, placebo-controlled study of its thermogenic, metabolic, and cardiovascular effects in healthy volunteers.
"In three studies caffeine was reported to stimulate energy expenditure and lipolysis in humans (5-7). Although Acheson et al (5) found that a cup of coffee (4 mg caffeine/kg body wt) consumed with a meal produced a significantly greater thermic response than that which followed the intake of the same meal with a cup of decaffeinated coffee, this difference can be almost totally accounted for by the thermic effect of the caffeine. Another study also found an increased energy expenditure by caffeinated coffee (100 mg caffeine) compared with decaffeinated coffee (6 mg) (6). The third study found a reduced thermogenic response to caffeine (4 mg/kg ideal body wt) in obese and postobese patients compared with lean control subjects (7)."
[Arne Astrup et al., Caffeine: a double-blind, placebo-controlled study of its thermogenic, metabolic, and cardiovascular effects in healthy volunteers, American Journal of Clinical Nutrition (l990), 51:759]
Changes in caffeine intake and long-term weight change in men and women
"Caffeine alone has several important metabolic effects. Caffeine is an adenosine-receptor antagonist (32), and all tissues with adenosine receptors can be affected by caffeine exposure. Spriet et al (33) reported that caffeine stimulates fat utilization in muscle tissue during exercise. In addition, Astrup et al (3) reported a dose-dependent increase in basal energy expenditure with caffeine intake in healthy subjects who had moderate habitual caffeine consumption."
[Esther Lopez-Garcia et al., Changes in caffeine intake and long-term weight change in men and women, American Journal of Clinical Nutrition (2006), 83:674–80.]