So what’s the take home in this? Caffeine/coffee intake appears to have different effects when looked at in the short and long term; looking only at acute dosing studies (esp with extremely high doses of caffeine) aren’t that relevant to how people actually consume caffeine (over the long term).
In the short-term, caffeine can impact positively on a number of factors (such as delaying fatigue during exercise, increasing lipolysis, and increasing fat oxidation and caloric expenditure) but negatively on others (decreased glucose tolerance/increased insulin response, slight increase in blood pressure).
However, longer term studies suggest that habitual caffeine/coffee intake is, overall, beneficial: it decreases the risk of diabetes and may contribute to preventing weight gain. Tangentially, of course, any benefit of coffee/caffeine itself is going to be more than outweighed if you fill it up with sugar, cream and other high calorie goodies.
My take on the topic: used in reasonable amounts, caffeine pretty much does nothing but help fat loss. The impact on insulin sensitivity is overstated (in my opinion) only applying to acute studies with massive doses. The known impact of caffeine on lipolysis and improving exercise performance is so well-established as to be beyond debate.
So use caffeine, just don’t go nuts with it.