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I have visited this topic before in Is Cardio Effective for Fat Loss and The ABSOLUTE Best Type of Cardio, but based on the comments I received and talking to others about the subject, I think that I need to bring it up one more time.
As I’ve said before, I think that cardio is overrated as a fat loss plan in general. For some people, it can be absolutely essential, but for the most part, most of your progress towards achieving your ideal body can be accomplished by other forms of activity and diet that involves minimal cardio. Not only is cardio not necessary for the most part, but toning it down a bit can be beneficial for your progress and get you closer to that body in less time, or at least allow you to keep more muscle mass while dieting.
First, let’s go over some reasons why you might want to keep cardio to a minimum when starting out your diet:
If you have a lot of fat to lose, and it is going to take a while to chisel down to the body you want, then cardio is actually pretty inefficient as far as lost calories are concerned. At a moderate pace, you could jog for an hour and burn off 400-500 calories, but instead of wasting all that time and energy you could have just eaten 200-250 calories less for a couple meals. Also, as long as you aren’t in that single digit bodyfat percentage yet, it wouldn’t really make much of a difference how you lost those calories; you would end up losing just about the same amount of fat from burning it from cardio vs. losing it though eating less.
If you think about muscle retention while dieting, then cardio becomes a problem here as well. Cardio will not only burn fat but also some muscle, even if you eat protein and carbs beforehand, though to a much lesser degree. While true that dieting in and of itself will burn off some muscle, the effect will be enhanced with a ton of cardio added on top of the diet. Also, in order to retain the maximum amount of muscle possible while dieting, your lifting sessions will need to be top notch. If you waste a lot of energy doing cardio, especially high intensity cardio, then the intensity of your lifting sessions might decrease, thus allowing even more muscle to be lost.
Lastly, cardio makes many people unhappy. For a large majority of people, performing cardio is much more of a chore than lifting is. If you are not one of these people, then this might not apply to you, but if you dislike cardio, then adding cardio into your routine might decrease your willpower further than it would have been without cardio. This can actually be a big problem because for many people, just sticking to the diet would solve most of their problems. In any case, dieting is not fun to do already, I would try to make it as easy on yourself as possible if you can.
Looking at the other side, there are definitely some reasons why you would want to incorporate cardio into your week:
I hinted above that if you had a lot of weight to lose, then losing a calorie is losing a calorie. It won’t really matter if you lose the calories due to dieting or cardio; your results will end up being almost identical (if not better for the non-cardio results, due to the other reasons above). However, the rules change a little bit when you get really lean. If you get down to the lower limits of bodyfat and want to keep going, then cardio might be necessary. At a high bodyfat level, the body doesn’t really care all too much about losing some fat – it’s not that big of a deal. When you get down to the lower limits of bodyfat levels, though, your body isn’t so willing to let go of even more fat – it would much rather just hand over some of that metabolically active muscle. Therefore, you might need to incorporate activity that shifts the caloric partitioning towards fat loss, like cardio.
Another more biological way of looking at this deals with the type of adrenoceptors in the bodyfat itself:
Different areas of bodyfat have different distributions of adrenoceptors, specifically beta-receptors and alpha-receptors. For simplicity, beta-receptors are good. They increase blood flow in the bodyfat and cause fat to be pulled out of the cells. Alpha-receptors are bad. They decrease blood flow and try to stop the cells from losing their fatty acids. When someone with a high bodyfat percentage starts out on their diet, they are going to have a lot of fat in many places that have a high percentage of beta-receptors, thus allowing fat to come off without too much of a problem. This person doesn’t need much cardio, if any at all, for the fat to come out of those cells with the high percentage of beta-receptors. However, when the person starts to get to a very low level of bodyfat, much of the fat that remains is stored in bodyfat that has a high percentage of alpha-receptors, specifically hips and thighs for girls and abs/lower back for guys in general.
Since a good majority of the fat that is left is high in alpha-receptors compared to beta-receptors, this person might have to change things up a bit.
Since he/she is at a very low bodyfat level, we wouldn’t want to lower the calories further. While lowering the calories might allow some more fat to come off, it will also push for muscle loss, something we are trying to avoid. So, this person can keep the calories the same, or even raise them slightly (still keeping them under maintenence, though) and then utilize cardio to make up for some of the loss in calories. Depending on a multitude of factors, the cardio can either be slow, steady state cardio or something more in line with HIIT (High Intensity Interval Training). Different people have different oppinions on both, and while there are definately some aspects of your diet and lifting that can almost dictate which type of cardio you should perform, one type is not inherently “better” than the other. It really just comes down to context.
Lastly, I want to mention that there are some times when you probably should start performing cardio right from the start of the diet and throught the diet. One of these times applies to people who have a bodyweigth that is pretty light to start with due to height, bone structure, etc. In general, some smaller girls who would need to hack off a fairly large chunck out of their normal daily amount of calories might not be able to afford to have all that reduction come from diet alone. This is because if the maintenance calorie level is 1800, for example, a 500 calorie decrease would leave the person with only 1300 cals/day. At this level, it might not be possible to get all the needed nutrients from food. This person should allow some of the drop in calories come from diet and some of the drop from cardio in order to get more vitamins and minerals from food everyday.
So now you should know that cardio is not a “magic pill” for weight or fat loss. In reality, losing calories from cardio tends to be harder than simply losing the calories due to diet. Furthermore, cardio has the ability to enhance muscle loss and lower the intensity or effectiveness of your lifting sessions. However, cardio can also play a role in calorie partitioning, especially at the lower levels of bodyfat, and can aid a person in getting some of the “stubborn” fat off. Also, cardio has many other health benefits, like increase your cardiovascular endurance, that might make it worth the trouble for you.
The main point here is that cardio should definately not be your first line of defense for losing fat. First, get your lifting and diet in order, then move to cardio if you so choose or if it will be benefical inside your context. (And yes, all of this applys to girls too. Even the lifting part.)