While it is true that many vegetables - including cucumber, celery, onions and leafy greens - are so low in calories that digesting them requires more energy than they supply, not even these negative calorie foods can match the impact on metabolism achieved with regular exercise.
Consider that you burn, at rest, 60 calories in one hour, and that you burn 100 calories by covering 1 mile on foot. It follows that if instead of sitting and watching your favorite sitcom, you were to go outside and walk/jog/run for this same length of time, even at the relatively slow pace of 10 minutes per mile, you would cover six miles and expend 600 calories by the time the show is over.
In other words, when you run, your metabolic rate is 10 times as fast as at rest, and possibly more, as energy expenditure increases progressively at higher speeds. In other other words, the faster your run, the more fuel you burn.
Let's look at this another way. In just 3 hours, a running man (or woman) burns the amount of calories (2,000) that it takes a resting person a full 24-hour period to expend. Lesson to be learned: if you want a fast-metabolism, get moving.
The champion of exercises, running is simple, effective and convenient. Anthropologists believe that the human form is a function of our ancestors' need to run. Whether running in search of food or so as not to become food, we ran. A lot. In fact, it was not uncommon for prehistoric man to run as much as 16 or 20 hours each day.
Over long distances, humans can outrun the fastest animals, at times even beating the horse, as the annual Man Against Horse 50-mile race in Arizona has shown. Other evidence - that we walk on two legs, have little body hair and lots of sweat glands, in addition to a nuchal ligament and a mobile 1st vertebral joint - all points to the same thing: We were born to run.
Now, you've probably been told not to run. Maybe you've even said it. Running will ruin your joints, some say. Others have remarked: I used to run, but it broke down my back. In fact, the opposite is true: today's set-up is totally unnatural. The sedentary life is ruining us. Sitting at a desk is leaving us stiff and bent over. We get old because we stop running. And recent research supports this, showing not only that running is not hard on the joints, but that it actually protects the joints! If you're not convinced, here's another link.
Running is our natural state, and yet few do it enough if at all. Instead, we spend 8 hours or more each day at the desk and in the car, with additional time slouched on the couch and scarfing grub at the table. Added to the 8 hours we sleep, this amounts to 16 to 20 hours per day or more spent on our backs and backsides. Back in Nature, we used to run that much!
Run any place, any time. Do it indoors or outdoors, rain or shine. At the park or in the mountains, up a hill, on a track, around your block or on your treadmill. All you need is the spirit of adventure (shoes are optional). Run soft and straight. Keep your head steady and let your arms gracefully sway at your sides as your feet touch down quickly and turn over rapidly. If this seems like too much instruction, just take your shoes off and run in the grass. Perfect form will come naturally.
An aside: we used to hate running. Even running so much as the President's mile, back in middle school, caused endless suffering. Well, not endless, but 8 minutes, which is how long it took to accomplish that grueling feat back then. But for those to whom running does not come naturally, take heed: running can be an acquired taste - like wine, or oysters, only better for you, and without the hangover or bad breath.
If you're still not convinced, try this: go to the park or beach, take off your shoes, and feel the breeze. Pavement awaits!