In this work, published in "Diabetes Care", 12 healthy people were studied who, after abstaining from caffeine for 72 hours, were injected with moderate doses of caffeine or an inactive substance. Caffeine reduced insulin sensitivity by 15%, a percentage comparable to the increase in sensitivity obtained with the drugs that diabetics receive.
The caffeine group also had higher levels of fatty acids and it is believed that caffeine’s ability to decrease insulin sensitivity is due to the fact that it stimulates the production of free fatty acids and adrenaline, blood levels of which were increased five-fold. in this study group.