There is a long standing belief that fasted cardio burns more fat, and therefore has favorable effects on body composition. What does the research tell us?
If you start the day with fasted cardio upon waking, with no intake of calories you will preferentially burn fat for energy while your train. Multiple studies support this, including this meta analysis.
In theory your glycogen stores are somewhat depleted in the morning so training on an empty stomach will force your body to source stored fat for fuel. So it’s understable that people would associate this practice with more fat loss over time and an improved body composition, right?
Acute fat oxidation post exercise doesn’t mean you stay a fat burning machine all day. There is research that shows over 24 hours, people who perform cardio fed, versus fasted, will see slightly higher levels of lipid utilization. You can read about this here.
So knowing this, why obsess over fasted cardio for short term benefits? If the goal is to change your body composition then we need to be focused on the long term outcomes and the behaviors that will help us reach our goals.
I personally prefer doing my training fed. Whether it’s hitting the weights in the garage, hopping on my paddle board on the lake, or running on the harbour waving at Husky The Musky, I’d much rather not be hungry!
In conclusion, the plan should be to follow a protocol that you can adhere to consistently. Even after you reach your goals. Sustained weight loss is more successful for folks who exercise. So if fasted cardio is your jam – do it! But if you need to eat first, then that’s the way to go. Dreading your fasted cardio means you’re less likely to do it, and everyone loses that way, especially you!