Whether you're trying to lose fat, improve cardiovascular health or reveal those abs (which requires low body fat), cardio is definitely a MUST do. However, before beginning a cardio program, it's best to take up weight training first to preserve or increase lean body mass (LBM). Cardio or aerobic exercise is basically any exercise that increases your heart rate and requires more oxygen intake to sustain for a certain period of time.
In terms of weight management or losing fat, in my experience, cardio is the ultimate fat loss accelerator, there is no doubt about it. Unless you have ectomorphic qualities or are genetically gifted and have a high metabolism, I find that it's always necessary to include cardio to lose fat. It ALWAYS BETTER to BURN OFF THE FAT, rather than try to starve it off (I've done this before, so I know). The latter will only lower your metabolism, cause plateaus when trying to lose fat and endanger your health.
Benefits of Cardio
1. Helps to directly burn fat WITHOUT lowering metabolism.
2. Naturally increases your metabolism.
3. Increases muscular endurance and stamina.
4. Aids in muscular recovery after weight training.
5. Triggers the release of endorphins, a hormone produced by the body that makes you FEEL GOOD afterwards.
6. Helps to relieve stress.
7. Improves cardiovascular health and lowers your resting heart rate.
When should you do cardio?
I'm a fan of doing cardio in the morning, before I eat anything. Here's why:
1. In the morning when you wake up, your body is in a fasted state because it has not received any food for 8-10 hours. This means your body's glycogen stores are low and thus, it dips into your fat stores for energy needed to sustain the workout. With less glycogen, more fat is burned. Therefore, it is the OPTIMAL time to perform cardio and target fat stores almost exclusively, as ratio of fat burned would be higher. In fact, you can burn up to 300% more fat when doing cardio in a fasted state.
2. As metabolism is elevated after morning cardio, your body continues to burn more calories throughout the day than when cardio is done later in the day.
3. If you do cardio later in the day, then your body will more likely burn off what you ate first, before targetting fat stores. So, fat ratio burned will be less and more carbs will be burned.
4. You are more fresh in the morning after waking up, rather than feeling tired after a day's work. So, doing cardio will feel much easier.
5. You will feel good and fresh throughout the day, since cardio triggers the release of endorphins.
6. You can get it out off the way early and not risk skipping it later in the day due to tiredness or [insert other excuses here].
7. Early morning cardio will help you regulate and suppress appetite.
Although early fasted cardio is ideal and optimal, it is just fine to do cardio at other times of the day. However, it is not recommended to perform cardio immediately after eating, wait 2-3 hours after you've eaten. Burning more fat or more carbs or whatever is a moot point if you're NOT even doing any cardio. The MAIN POINT is to just DO IT AND BURN CALORIES, regardless if it comes from fat or carbs. Some people argue too much about this and don't even bother doing it. The MOST IMPORTANT thing is that you DO IT and be CONSISTENT FOR RESULTS!
What type of cardio to do?
Some examples of cardio exercises: fast walking, jogging, running, sprinting (HIIT), hiking, cycling etc. These are common and effective cardio exercise, some more intense and effective than others but this also depends on individual results.
There are many arguments on which is the best or most effective form of cardio. Some say HIIT is most effective (currently most popular), some say running for miles work best, others say playing sports is better and so on. Let me just say that ALL FORMS OF CARDIO WILL WORK! It just depends on your fitness levels, choosing what suits you best and finding something that you enjoy doing. For me personally, I love outdoor running early in the morning for 40-45 mins or hiking during the weekend.
The BOTTOMLINE is and key to losing fat is BURNING CALORIES! Cardio or activities such as sports that burns a lot of calories should be included if you want to shed fat.
How must cardio should I do?
If you're a beginner, start out with 3 days a week and do something that suits your fitness level. If you're never exercised in a long time, you can do something as simple as walking and move on to jogging. You can even start to take up some sports like basketball, football or swimming. Basically, start to MOVE and burn calories!
Like weight training, it's also important to progress in cardio. You can continue to improve on your cardio by increasing frequency (do it more times per week), increasing intensity(move from walk to jog to running etc) or increasing duration(from 30 mins to 45 mins etc).
For maximum fat loss, most people say it's beneficial to do cardio daily, for about 5-6 days per week (only if your fitness levels are good). This is very true, since your body is able to recover faster with cardio and you can burn more total calories per week. However, I believe that the amount of cardio you need to do should DEPEND INDIVIDUAL RESULTS. If you're getting good results by doing 2-3 days per week, then you don't have to do more (unless you want to speed things up). If 5-6 days is what you need, then DO IT! Basically, do JUST WHAT YOU NEED to get results. However, please be aware that with such frequent cardio, you need to make sure that you're eating well and getting enough rest. If you feel like you're killing yourself with cardio, you need to decrease either your frequency, intensity or duration. You can even take a break for a week or 2 and rest more to recover. Over-training will only hold you back and derail you!
Won't cardio burn off my muscles?
I've heard this a lot and I agree that cardio can be a double-edged sword, if your approach is wrong. When trying to lose fat, a small loss of muscle is usually inevitable and this is NOT caused by cardio alone, but is also caused inadequate caloric and protein. How do we go about this?
1. Depending on the individual, you can either decrease the amount of cardio (if you're doing too much) or increase caloric intake, especially protein to support your muscles.
2. Do not lower carbs too much as well since your body will burn protein if glycogen levels are constantly low. A moderate carb diet will do if you're consistently doing cardio.
3. If you're worried about burning muscle when doing fasted cardio, you can have a 100% whey protein shake (with little or no carbs) before you begin.
The issue of muscle loss is more related to someone who has a lot of muscle and will need to more carefully monitor their progress to avert a substantial loss of muscle. Average gym goers who have a moderate amount of muscle need not worry so much =)