For all the different things that we're told can slow down our metabolism, there seem to be countless more pointers on how to rev it back up. (Eat spicy food! Try interval training! Balance your hormones!) Some of these tips (including the ones mentioned above) are backed by science; others are a bit more anecdotal. But the vast majority of them require some semblance of effort, whether it's selecting the right kinds of food or working out in a certain way.
Now for the obvious question: How slow is slow enough? It'll take your brain about 20 minutes to register how full it is, so try to stretch out your meal for at least that long. A 2011 study also showed that participants who chewed each bite 40 times lost 12% more fat than those who chewed 15 times, so aim high.