Should I do cardio while fasting?

Author: Annamarie Wisozk  |  Last update: Wednesday, September 3, 2025

Fasted cardio causes fatigue and exhaustion much faster than exercising in a fed state. Given the high intensity and heart rate associated with cardio training, when glucose and carbohydrates aren't available to use as energy, you're more likely to feel tired, weak, sore and even potentially lightheaded or nauseous.

What happens when you do cardio while fasting?

Research has shown that there is no difference in body-fat loss between fasted and fed cardio. Fasted cardio may burn more fat during the time of the actual workout but less the rest of the day, whereas non-fasted cardio may burn less fat during the workout but more throughout the day.

How much cardio should I do while fasting?

Fasted Cardio Tips to Keep In Mind

Stick to workouts that are 30 minutes or less, Schlichter suggests.

Will I lose muscle if I do cardio while fasting?

In summary, while fasted cardio can potentially lead to muscle loss, especially if not paired with proper nutrition and training, adequate protein intake and a well-rounded diet can help preserve muscle mass.

Is fasted cardio pointless?

Fasted cardio involves working out on an empty stomach, typically first thing in the morning. Some experts and fitness enthusiasts claim that this allows you to burn more fat and calories than working out after you've eaten. Currently, there is not enough scientific evidence to support these claims.

Does FASTED Cardio Burn More Fat? (What The Science Says)

What is the 30 30 30 rule?

That plan is called the 30-30-30 rule. It's a simple but catchy idea that encourages you to eat 30 grams of protein within 30 minutes of waking up and then get 30 minutes of low-intensity exercise. The 30-30-30 rule now has millions of followers on TikTok.

Does fasted cardio burn belly fat?

That's why it's often thought that fasted cardio may boost fat loss, though current research on that is mixed. Roper agreed that the research has been inconclusive about whether exercising on an empty stomach actually burns more fat.

Do you burn more fat if you exercise while fasting?

One study found that exercising in a fasted state also led to a higher fat loss than in people exercising after a meal. However, other studies have produced different results. A 2014 study found that people who fasted overnight and exercised did not lose more weight than people who ate before exercise.

Why do bodybuilders do fasted cardio?

Bodybuilders. Why has fasted cardio become THE answer? Largely because the bodybuilding fraternity, many of which will have been well under 10% bodyfat, have utilised fasted cardio to help with the mobilisation and transport issues suffered by lean people mentioned above.

Is cardio good while intermittent fasting?

While fasted lifting is a big fat mistake, fasted cardio is fine—but know that fat burning and fat loss are not the same. This means your body is burning fat as an energy source—and, without a calorie deficit, those stores will be replenished.

Should I lift weights while fasting?

I would say people who are fasting should strength train,” Horowitz adds. Fasted strength training also tends to prompt the body to rely more on fat than carbs—similar to fasted cardio—so the strategy may help with body composition if fat loss is your goal, some research shows.

Will I lose muscle if I do cardio on an empty stomach?

Muscle breakdown.

This means your body can just as easily break down your muscle stores and tissue, liberating stored glucose to use as fuel in your fasted cardio sessions. That means, not only are you not burning your body's fat stores, you're actually breaking down your own muscle as well.

How long should I do fasted cardio?

The risks of doing long fasted cardio sessions include muscle breakdown (catabolism), low blood sugar, and low energy levels. Since one of the big benefits of fasted cardio is time efficiency, aim to keep your fasted cardio sessions to 30 minutes.

At what stage of fasting do you burn fat?

Fat burning typically begins after approximately 12 hours of fasting and escalates between 16 and 24 hours of fasting.

Is fasted cardio bad for you?

The choice to practice fasted cardio is a personal decision. Performing exercise consistently, regardless of whether or not you eat before, provides clear health benefits, including healthy, sustainable weight loss. If you have never done a workout before eating breakfast, it's best to start slow.

Does belly fat burn during fasting?

Fasting triggers a process known as lipolysis, where the body begins to break down and burn fat for energy, instead of relying on glucose from food. This can lead to significant weight loss, especially around the midsection where stubborn belly fat tends to accumulate.

Is it better to eat breakfast or skip breakfast for weight loss?

Studies show that most people who lose weight and keep the weight off eat breakfast every day. On the other hand, you need to pay attention to what, when, and how much you eat. One study showed that people who had large breakfasts ate more during the day.

Do you lose muscle during fasted cardio?

What the research says. A beta-analysis from 2017 looking at five studies on fasted versus fed exercise concluded that working out fasted does not result in greater weight loss or changes in lean muscle mass or fat mass.

Should I do cardio on an empty stomach?

If you're going to be working out for longer than an hour or so, you'll want to have enough fuel to sustain the entire workout. So to sum it up, if your cardio of choice is an intense yoga session or a moderate-intensity cycling circuit, cardio on an empty stomach could be a great choice!

What is 30g protein 30 minutes waking up?

When it comes to nutrition advice via social media, trust me, I've heard worse. The 30-30-30 method refers to consuming 30 grams of protein within 30 minutes of waking, followed by 30 minutes of low-intensity exercise. Biologist Gary Brecka describes the diet on TikTok, which now has more than 17 million views.

What is considered low intensity cardio?

Some examples of low-intensity workouts are walking, bicycling, swimming, rowing, yoga, tai-chi, and resistance training. Such activities improve blood flow, prevent muscle wasting, and prevent falls and injuries.

Is the 4 hour body diet healthy?

4-Hour Body Diet: Health Risks

Restricting entire food groups could lead to deficiencies in certain vitamins and other nutrients, including vitamin D and calcium (found in dairy) and B vitamins such as folic acid (found in grains and fruit).

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