Fasted Cardio

Fasted training has become more popular over the years as a way to increase fat loss. But fasting before your training does not seem to directly enhance fat loss and may even impair strength performance.
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A 2014 study compared the effects of fasted VS fed cardio while matching the daily calorie and macronutrient intake of the participants. Both groups lost a similar amount of fat [1]. As the researchers point out, the human body constantly adjusts its fuel source. If your body uses more fat for energy during fasted training in the morning, you burn less fat later in the day once you eat more calories (assuming someone is tracking their calorie intake).
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The only way fasted training can boost fat loss is by helping you reduce your daily calorie intake. Those that train fasted tend to have an easier time keeping their calories down since they skip an entire breakfast meal [2].
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Now, when it comes to strength performance, a 2019 study found that people used to having breakfast tend to perform worse in their training when they have a fasted workout [3]. So if you normally eat something before training in the morning, fasted workouts likely harm your performance. It is possible that you get used to fasted training over time the more you do it. Having a cup of black coffee before a fasted workout may also help, but there is no research on this to date.
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The way I would see fasted training is as another tool in your “fat loss toolbelt”. If fasted training helps you better control your calorie intake and you enjoy doing it, go for it. But if you dislike fasted training, there is no need to do it.
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