Fasted cardio is a topic that has been widely discussed in the fitness community. It simply refers to undertaking a cardiovascular exercise, such as running, while the body is in a physiological state of fasting, typically early in the morning. The belief that has popularized this form of cardio is that lipolysis, or fat loss, is more efficient in this fasted state.
The benefits of a morning run have been sung so vocally, and it is not unusual to correlate those with fasted cardio. Making your body endure 30 minutes of moderate to intense activity without any ready supply of glucose will cause your body turn to fat for energy. Thus it will encourage more significant losses in fat, leading to a leaner physique. This is the argument presented, but how much truth does it hold?
What Are Your Goals?
If you are overweight and are looking to lose those extra pounds of fat, fasted cardio is heartily recommended. As it has demonstrated that it can lead to weight loss, this form of cardio can prove effective if you are all about slimming down your waistline. However, if you are a bodybuilder, you should tread this ground much more carefully.
While it is true that fasted cardio leads to lipolysis, fat is not the only thing that is lost. Intense cardio on an empty stomach will have a catabolic effect, and can lead to loss of muscle. The reason for this is that the energy demands placed on your body cannot be fully satisfied by the breakdown of fat alone. This, physiologically speaking, is not a very effective process of providing energy, and when it is needed in large amounts, muscle protein is used, leading to muscle loss.
Also, there is the adaptation part of the equation. When you are used to fasted cardio in the morning, your body will adapt. It will become aware of the energy required after fasting and will consequently preserve more glucose to address this demand. Thus the excess energy you get from your meals will be stored to provide energy for your morning run.
A lot of information you will get on the subject will be mostly contradictive. While one source will advocate for fasted cardio because of the involvement of insulin and cortisol, another will shun it, asserting that the thermogenic effect of exercise is enhanced when food is consumed beforehand.
Truth is, there is a place for fasted cardio. If you keep your sessions short, and the intensity moderate, this type of cardio will not eat into your muscle gains. But if you prefer HIIT cardio, you are better off eating an hour before you begin. This will prevent any muscle loss. Alternatively, you can take a BCAA or whey protein supplement before starting your cardiovascular exercise to forestall any muscle losses.
Needless to say, cardio is much more comfortable when you have energy resources to draw from. Since the number of calories burnt will be consistent regardless of whether you are fasted or not, eating before is encouraged.
Your fitness pal