Muscle Evolved

Is It Bad to Work Out Fasted? Everything You Need to Know

By Caleb Hester · · Updated

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Whether it be a personal preference, or maybe life gets in the way and getting your “proper” meals in at the right times just doesn’t work out, some individuals may find themselves working out without any pre-workout meals.

In the bodybuilding and powerlifting communities, working out fasted is often looked down upon just because of the lack of stored energy and carb intake for fueling your workout, but with more research, what does the science say?

Whether you are here looking to build muscle or lose weight, in this article, we will answer whether working out fasted is good or bad.

Is it Bad to Workout Fasted?

Is it Bad To Workout Fasted?

No, it is not bad for most healthy people, but it is not magic either. Fasted exercise increases lipolysis (the release of fat from fat tissue) and makes your body burn a larger share of fat during the workout.

That does not mean you lose more body fat over time. In a four-week study of fasted versus fed cardio, both groups lost similar amounts of fat while eating in a calorie deficit.

A 2020 review in Open Acess J Sports Med found that fasting does reduce body weight and fat, but it can reduce lean mass too. Results on endurance performance were mixed: some studies showed a drop, others no change.

The authors recommended that endurance athletes avoid high-intensity training while fasting and keep fasted sessions at lower intensity.

Bottom line: if you train hard or long, eat first. If you prefer light workouts before breakfast, fasted training is a fine option, as long as your overall diet supports your goals.

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Can You Still Lift Heavy When Working Out Fasted?

Is it Bad To Workout Fasted?

Technically, yes. Many people lift in the morning without eating and do fine, especially in shorter sessions. Some people do feel weaker or lightheaded without food, so pay attention to how you respond.

A 2018 review and meta-analysis in Scand J Med Sci Sports looked at 46 studies. Eating before exercise improved performance in prolonged aerobic exercise, but not in shorter sessions. Fasted exercise raised the level of fatty acids in the blood after the workout.

The bottom line: if you plan a long or very intense session, a pre-workout meal will likely help. If you train fasted, a protein-rich meal afterward helps your muscles recover.

Keep a can of energy drink handy, in case you need one!

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Benefits of Working Out Fasted

Working out fasted increases the share of fat you burn during exercise and raises fatty acids in your blood afterward. Researchers are also studying whether it leads to helpful metabolic changes in muscle over time.

For many people, the biggest benefit is practical: it is convenient, and some people simply feel better training on an empty stomach. Stay hydrated, and keep fasted sessions on the lighter side.

Cons of Working Out Fasted

Working out fasting, although has benefits, also has cons depending on what you are doing. Fasted workouts are not good for prolonged workout sessions or high-intensity “athlete level” workouts.

Long sessions are where eating first helps most, so if you train fasted, keep your workouts shorter.

If your goal is to build muscle, your total daily protein and calories matter more than whether you ate before training. Fasted training can make it harder to eat enough, so plan your meals carefully.

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