1) To raise the metabolism?
2) To burn fat stores?
#1 would entail doing high-interval training, maybe even with some carbs in the belly for energy. You'd train for 16 minutes (I'm talking maxOT) on a stationary bike, very high intensity on intervals.
#2 would entail doing 45 min of cardio first thing in the morning on an empty stomach. The body would have no food in the belly so it would use fat stores. Low intensity cardio.
I believe most people use method #1. Makes sense . But #2 seems like a better long-term solution, doesn't it? Thoughts? Also, an answer like "both" isn't what I'm seeking here.
Let me give you an alternative response, which is basically a version of #1:
To increase the general fitness level.
Doing so through various forms of cardio, and this could be sprints, walks, long walks, shorter walks ,
a game of hoops.
Getting your cardiovascular health primed, will give you a better fat loss ratio once you keep your calories balance in the negative.
And overall wellness will be improved, as well as slight quicker recovery after workouts.
I usually take a brisk walk for 20-30 minutes in the morning, 2-4 times a week. Not to lose fat, but rather to speed up recovery and get a better overall health.
I can't do high intensity cardio, as I am training for fast twitch muscle fibers only, but I have in the past, and it's very effective IMO.