Caffeine elevates/releases blood sugar. In some, it will be enough to force the release of insulin, then the sugar rollar coaster ride ensures. End result, appetite increase. Also "one" of the reasons people crash a few hours after some short-acting stims; not just b/c the stim runs out but because of the sugar crash (acute hypoglycemia).
Coffee can increase insulin sensitivity but that doesnt mean it cannot do the aforementioned "acutely" as well.