If you're in somewhat decent shape and don't have any medical limitations, the most effective way to exercise is to do short bursts of the high-end of moderate intensity, or if you're in very good shape, the low-end of high intensity. 

An example would be jumping rope or jumping in place, or running up stadium steps, or sprints on the treadmill or stationary bike. 

Medical studies have proven that performing two or three abbreviated workout sessions of 10 minutes is not only just as effective as one prolonged exercise session, it's actually more effective. 

Other studies have proven that even if you manage to hit the gym a few times a week for an hour or so, if the rest of the time you're sitting on your keister at work, you increase the chances of dying prematurely. 

Performing short bursts of exercise not only increases your metabolism, it keeps fresh blood moving throughout the body, thus preventing pooling and stagnation (one cause of pain and stiffness), and can help prolong your life. 

It doesn't matter what activity you're doing, as long as it gets the heart rate really going. Your maximum target heart rate is theoretically around 220. If you can get your heart going for a minute or two at a clip at about 65-80% of your maximum heart rate (say 165-180 beats per minute), you are doing short bursts of exercise. 

After the 60-90 seconds at this heart-pounding pace, allow your heart rate to come back down to Earth until you catch your breath and have enough energy to perform another round of short-burst high-intensity exercise. If you do even just a few rounds, it'll only take about five minutes. But do this a few times during the day, and you'll notice a remarkable improvement in your cardiovascular capacity, and within a couple weeks, you should likely notice a difference in your increased fat-burning. 

Make sure, though, that you allow your heart rate to come back down. Prolonged high-intensity exercise is stressful to the body. Even though you're exercising, your system does not distinguish between stressors; stress is stress, be it financial or physical. 

And this is where stress management plays an important part in weight loss. Prolonged stress can hinder metabolism, primarily because of hormone levels wildly fluctuating and not following normal hormonal pathways. 

Obviously nutrition plays a very big role in weight loss. But just as important, and what many fail to consider, is stress management also helps with weight loss. 

People who exercise at a high intensity level need lots of time to rest in order for the body to repair. If you have a very stressful life (kids, bills, nagging spouse and boss, etc.) exercise is a great way to manage stress. But it's a double-edged sword. If you really want to fit in those skinny jeans, you need to perform more higher intensity exercises to jack up your fat-burning furnace. But that high intensity exercise is a stressor. 

In addition to getting enough sleep and vitamins and minerals from whole foods, you also need other stress-mitigating activities such as meditation or other mindfulness practices like Tai Chi or Qi Gong. 

Journaling or gardening or any other activity that can lower your blood pressure and make you realize that your problems are a pimple in the grand scheme of the universe!