Does Fasted Cardio Really Burn More Fat?

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Does Fasted Cardio Really Burn More Fat?

On the surface, it seems to make sense. Exercise first thing in the morning on an empty stomach and your body should burn more fat. After all, without food intake for eight to 12 hours, you are in a fasted state. With glycogen stores depleted and low morning insulin levels, your body has to turn to other energy sources to power through your workout, and it’s more likely to turn to fat for fuel.

Fasted cardio is a technique that has been around for years in the bodybuilding community, and one that’s gaining popularity among regular gym goers and even endurance athletes. But will forgoing your morning oatmeal really lead to a leaner body and better athletic performance?

Here’s the skinny on sweating it out sans food and whether or not it is suitable for your body and fitness goals.

The Fast Track to Fat Loss?

Early morning, un-fueled workouts are a common protocol among bodybuilders, especially in preparation for competition when they need to lean out as much as possible before they walk on stage. Some celebrities also turn to this technique to get ready for their close-up, whether that’s a photo shoot or red carpet event.

“Is fasted cardio a good way to burn fat? The answer is yes and the answer is also no,” says Jay Cardiello, a NSCA and ISSA-certified strength and conditioning and fitness expert who has worked with celebrities such as Jennifer Lopez, Curtis “50 Cent” Jackson and Sofia Vergara. “It’s effective, but it’s not sustainable,” he says.

Some studies have found that exercising in a fasted state can burn almost 20 percent more fat to exercising with fuel in the tank. Why? Once we eat, insulin (which regulates the breakdown of fat) increases in our body. And, according to some research, higher insulin levels have been shown to suppress fat metabolism by up to 22 percent.

However, research has demonstrated that fasted cardio does not increase fat burning over a 24-hour period. While your muscles adapt to using more fat when you exercise, you don’t actually lose more fat overall on the days that you exercise compared to days that you don’t. Another study suggests that ingesting carbs before working out increases the post-exercise “afterburn” effect more than the fasted state. That means more calories burned throughout the day, not just during your sweat session.   —Christine Yu for Life by DailyBurn

Want more? Head over to Life by DailyBurn to learn whether or not fasted cardio really burns more fat.

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  • Philip

    If fat burning is accelerated during a workout but not over the 24-hour period during which the workout takes place, does that mean that fat is burned more slowly throughout the rest of the day?

    • Sanne

      Throughout the rest of the day your insulin levels rise. So if we’re going by the suggestion in the article that insulin inhibits fat metabolism, then logically it does mean fat is burned more slowly when your insulin levels are heightened during the day.

    • Rica J Gilmore

      Your body burns fat at a specific rate all day long.
      When you do a fasting working out, you burn more than normal and more that a non-fasting working. You do not burn more or less than your normal fat burning rate. (It is still effective. — You will still do good as bluehenjen stated in his perfect example).
      When you don’t fast, you burn almost as much as the person doing a fasting working for the actual work out duration PLUS you also increase your specific normal rate all day long. This is the added bonus you get (the sustainability).

  • So whats the conclusion of the article? Their is no added benefit to fasted cardio over a non-fasted cardio session?!

  • Sarah

    You’re supposed to weight lift fasted, not do cardio..

    • Jenny

      I went to lift weights yesterday without eating breakfast and I almost passed out. Hypoglycemia can be dangerous.

  • Kelly

    I’m not sure I agree with this article. Generally, when you do cardio exercise the energy produced for the first 20 minutes or so comes from anaerobic cellular respiration which uses (mostly) glucose for energy and does not include the breakdown of fatty acids. Beyond 20 minutes the body relies on aerobic cellular respiration which does involve the breakdown of fatty acids. Regardless of whether you have eaten recently or not if the body needs to produce insulin to mobilize glucose then it will produce insulin. If you have been eating a VERY low carb diet and have depleted carbohydrate (aka glucose) stores from your body (or if, like myself, you have Type 1 diabetes and don’t produce any insulin) then you will burn fat stores during the first 20 minutes of your workout. THIS IS VERY DANGEROUS!! The by-products of this process are ketone bodies which can cause a dangerous increase in the acidity of the blood which, among other things, can cause irreversible damage to your kidneys.

    • Lee

      Kelly sounds like she knows what she’s talking about!

  • bluehenjen

    I’ve been reading about this topic for years and my advice is: do whatever works best for you. I work very long hours and must get to the gym first thing in the morning or it won’t happen. I’m not going to wake up at 4 am to make sure I can have some oatmeal and banana at least 30 minutes before my workout. I do both heavy lifting and cardio in a fasted state and then consume good protein within 30 minutes of ending my workout, and have always been happy with my performance and feel good. If someone else feels better eating before a workout, that’s also fine. Listen to your own body, not what someone else tells you…especially when so many of the experts disagree.

    • Victoria

      I’m right with you. I’ve always gone on my runs and done my strength first thing in the morning. I didn’t even know being “fasted” was a thing. I like feeling empty in the morning and breakfast tastes soooo good.

  • jojoalicid

    I’m really confused… I may have read this wrong, but what was the actual conclusion? I also don’t understand the entire last paragraph, lol. What does it mean that once your muscles adapt to using more fat, you don’t lose more fat on days you exercise than don’t? How is that possible?… If you’re using the fat then aren’t you losing it & then when you’re not using it you’re not losing it? I’m sorry if these are stupid questions, but I just don’t understand what’s being said here.

  • My Name Is Oliver Queen

    What I find works best for me is to do a 2-1 ratio of non-fasted to fasted cardio (2 days of a 400 calorie breakfast which includes a protein shake before cardio, then 1 day fasted cardio, repeat, etc). I no longer have any problems with lethargy in the morning during workouts on fasted day like I used to when I was doing more fasted than not days.

  • Mark

    I don’t know but I have fasted prior, consumed small amounts if carbs prior and consumed protein smoothies during my workouts. I found for me taking in a small amount of whole grain carbs prior to a cardio workout and weight training on an empty stomach then consuming a protein smoothy/shake after works best. But that’s me. Like “Bluehenjen” said, it all personal preference. Figure out what your body responds to and go with it.

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  • Lara

    So…the conclusion is inconclusive? I guess just go with what works for you. 😀

  • Adriana

    I can’t eat before working out. I get cramps. Morning work outs are best before breakfast for me. If I can’t then I must wait 3 hours after dinner before exercising. If I don’t I pay for it big time.

  • Margie Ponds

    I was overweight and tried so many things. Different things work for different people and I was lucky enough to find one that worked for me. I lost 25 pounds in one month without much exercise and it has been a life changer. I’m a little embarrased to post my before and after photos here but if anyone actually cares to hear what I’ve been doing then I’d be happy to help in any way. Just shoot me an email at oceanflowers82@gmail.com and I’ll show you my before and after photos, and tell you about how things are going for me with the stuff I’ve tried. I wish someone would have helped me out when I was struggling to find a solution so if I can help you then it would make my day