Effects of caffeinated and decaffeinated coffee on biological risk factors for type 2 diabetes: a randomized controlled trial.

In 45 nearly obese persons (habitual coffee drinkers) with the average age of 40, consumption of 5 cups of caffeinated coffee was associated with increased adiponectin concentrations relative to control but not to decaffeinated coffee (likely indicative of another bioactive).

Effects on insulin sensitivity and blood glucose did not differ caffeinated and decaffeinated coffee, although decaffeinated coffee was associated with a significant drop in diastolic blood pressure relative to control and caffeinated.