Cardio is short for Cardiovascular Exercise - Basically any exercise which uses the whole body and get your blood pumping hard (hence why it is "cardiovascular"). Examples include jogging, running, swimming, cycling, aerobics, rowing, hiking, walking, climbing, including various sports such as basketball, javelin throwing, wrestling, boxing, shot put, etc. It even includes sex.
Will Cardio Make Me Fat?
No. Cardio exercises burns a lot of calories (usually from sugar, fat or carbohydrates). CARDIO BURNS FAT.
What kind of Cardio Exercise is Best?
There isn't one. Indeed, I question overconfident trainers who think that only one form of exercise is right for every person, especially with the industry's habit of changing its mind and all the new exercise fads that come out each year. There isn't one type of cardio exercise that is good for everyone. What is more important is finding cardio exercises that you enjoy doing on a daily basis and will give you a broad range of ways to exercise your whole body.
Fitness isn't black or white and if there is one thing I have learned it's that every answer comes with a big fat "but" and several exceptions.
Now some people in the exercise industry like to argue (and spread misinformation) that cardio can make you fat. Here is the 3 reasons why they think that:
Cardio raises cortisol in the body because physical stress releases this hormone from the adrenal gland, which in turn makes it more difficult to burn fat. However, every exercise does this, not just cardio. You get out of your bed in the morning and take the dog for a walk and this happens. Should you stop exercising? Heck no! BUT (there's the keyword) you have to know how to manage exercise and balance your nutrition to control the release of cortisol.
What has been happening in the fitness industry is that weight trainers have been spreading misinformation that strength training will achieve every result that you could ever want instead of cardio and are trying to argue that weight training is the be all and end all of fitness. And they are omitting the fact that weight training also releases cortisol.
Yes, you will feel hungrier after you exercise. That is why diet and discipline is so important. You can go to the gym, burn 300 calories, and then eat a 1,000 calories worth of bacon afterwards. You're not going to get thinner that way.
When we exercise we burn through our lunch first (carbohydrates, sugar, glycogen) and then we burn through fat (after about 20 minutes after exercise) which is our body's primary fuel source. So yes, you will feel hungrier if you exercise for over 20 minutes.
Pff. All exercises help you to tone and strengthen muscles. Yes, weight training will bulk you up faster in specific muscles, but its not very good at burning fat. Exercising will never cause you to "lose muscle". If your arms, legs and belly are looking thinner because you're doing cardio... that isn't muscle you are losing, its a layer of fat under the skin that has become thinner.
If you are super thin (anorexic) and you don't have any fat stored up your body will burn protein, otherwise known as muscle, as an energy source. However, the metabolic and fat burning process is not simple. To burn muscle you would have to do cardio for a very long time and burn off all of your most recent meal and all of your fat stores. So yes, it is possible to burn muscle doing exercises (any exercises, not just cardio), but you would have to be thin and starving to do it.
When you look at groups of exercisers as a whole (not on an individual basis) different exercises produce different body types:
Ideally what you want is a mix of both worlds, cardio and strength training together. Cardio is by far the easiest for most people to do whereas weight training requires finding yourself something heavy to lift on a regular basis (this is why mothers often develop what some people call "mommy arms" that are surprisingly strong because they're lifting their kids up regularly).
Many body builders are afraid of losing the muscle that they have worked hard for. Unfortunately many body builders place so much emphasis on muscular aesthetics that they have terrible cardiovascular health (meaning they have a weak heart).
This explains why Arnold Schwarzenegger had a heart attack in 1997 at the age of 50. He might be "The Running Man", but he wasn't doing enough cardio to make his heart stronger.
No one should ever blindly trust their doctor, personal trainer, nutritionist or the guy that looks good in the weight room. Read, research and experiment with different types of exercise. Find a balance that works for you.