Fitness Essential or Myth: Fasted Cardio
Fitness Essential or Myth: Fasted Cardio
Is fasted cardio the best way to burn fat? Some people swear by it and others are quite skeptical.
What is Fasted Cardio?
Fasted cardio is doing aerobic (cardiovascular) exercise before eating your first meal of the day. This is done on an empty stomach so that your body uses fat instead of food.
Using Fat as an Energy Source for Exercise
Your body has several different energy sources. Carbohydrates are the ideal source because it takes less oxygen to convert into energy. If you are doing intense exercise oxygen is being used at a faster rate therefore carbohydrates are used because they use less of it. During lower or medium-intensity exercise fat is more likely to be used due to it having twice the potential energy as carbohydrates. The body can use this energy when more oxygen is available in lower-intensity exercise. Using converted food nutrients first and then it will start using stored fat in the body.
Ideal Fasted Cardio
Knowing your body takes about 12-16 hours to enter into a “fasted” state (or ketosis), not all morning fasted cardio may be fasted cardio. When your body starts burning fat as an energy source it is referred to as fat oxidation. Maximum fat oxidation occurs between 45 and 65% of your VO2 Max or around 50-70% of your max heart rate. This is a pace where your breathing has increased but you can still talk.
Studies
Cambridge University Press (2016)
This study did show that fasted cardio and low-to-medium intensities did increase fat oxidation than exercise in a fed state. With fax oxidation occurring sooner into exercise than in a fed state.
Ketogenic Diets and Exercise Performance (2019)
This study did show that ketogenic diets, or diets that focus on fats as a primary energy source, did prove to reduce body weight and fat mass. By fasting you are putting your body into this state therefore it seems relevant to include this study. While fat loss was increased performance and lean body mass/hypertrophy decreased in this state.
Conclusion
ESSENTIAL - Fasted cardio is beneficial for fat loss. The studies do show improved fat oxidation and reduction in body fat over periods when doing fasted cardio. Some articles show the results are minimal but almost all the studies suggest fat loss is improved to some degree. The results from 5-20% greater fat loss for fasted cardio vs. fed cardio.
A NOTE OF CAUTION is that being fasted has been shown to decrease high-intensity performance and also worsen or negatively impact hypertrophy (muscle building) results.
What is Fasted Cardio?
Fasted cardio is doing aerobic (cardiovascular) exercise before eating your first meal of the day.