The Answer Is No And Heres Why:
During a workout, you break down your muscle fibres and deplete your glycogen stores which can leave you feeling sore and fatigued. Because your feel tired and your muscles are sore, it would make sense to eat right away, right?
WRONG! There are actually NO BENEFITS of eating right after your workout!
Losing Weight And Body Fat
When you havent eaten for a long time, like after an overnight fast, your body is primed to burn fat. You use energy from your fat stores instead of relying on the carbs from your last meal. When you havent eaten for hours, your insulin levels are low, your glucose stores and blood sugar levels are down, and your blood is full of fatty acids. Combined, that means you oxidize, or burn, more fat when exercising in the fasted state than when youve eaten.12
Burning more fat during exercise sounds great if you want to lose weight, doesnt it? But hold on, its not that easy. Fasted exercise, combined with a calorie deficit, is an excellent option when you want to lose fat, but its probably not more effective than exercising at any other time.34
Scientific evidence does not support morning workouts or exercising on an empty stomach as a superior way to improve your body composition. Unfortunately, your body is too intelligent to be tricked like that. Undoubtedly, you burn more fat during the exercise when performed during your fasting window. But fat burning must be considered over the course of days, not on an hour-to-hour basis. If you look at the day as a whole, your body compensates by burning less fat or storing more fat during the rest of the day after fasted exercise. The result is no difference in fat loss over time.
But what about your muscle mass?
Benefits Of Fasting For Metabolic Health And Beyond
IF practices have demonstrated short-term positive impacts on patients metabolic health, with a recent systematic review reporting significant reductions in weight and waist circumference in overweight/obese patients. These findings were reproduced in both calorie restricted and eucaloric regimes, indicating a physiological benefit independent of reduced caloric intake. Thirty days of eucaloric IF in healthy volunteers has been associated with improved proteomic signatures and the upregulation of proteins involved in immune system regulation and DNA repair . It is hypothesised that this effect may improve individuals health by reducing the risk of developing long-term conditions related to chronic inflammation.
The interplay between IF and metabolic regulation may involve the circadian system. Recent studies on circadian rhythms have shown a diurnal variation of insulin and blood glucose levels. This raises the possibility of a time-of-day variation in the metabolic response to calorie consumption which is independent of the amount eaten. This hypothesis is supported by the finding of an increase in adiponectin following TRE in physically active participants. This finding may also provide a practical example of the aforementioned circadian rhythm hypothesis.
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Training In The Fasted State
Studies are starting to demonstrate the benefits of such training. For example, one study looked at muscle fibres both before and after training in the fasted state. This means that you fast for a certain period of time, usually around 24 hours, and then do your endurance or other training. The combination of low insulin and high adrenalin levels created by the fasted state stimulates adipose tissue lipolysis and peripheral fat oxidation .
Other studies had already shown that the breakdown of intramyocellular lipids is increased by training in the fasted state. Six weeks of training in the fasted state also induced a greater increase of fatty acid binding protein and uncoupling-protein-3 content in muscle.
What does this mean in plain English? It means that our bodies have the ability to adapt to whats available. When we fast, we deplete much of the stored sugar . Our muscles then become much more efficient at using fat for energy. This happens because muscle learns how to use the fat as energy by increasing the amount of proteins that metabolize that fat. In other words, our muscles learn to burn fat, not sugar.
Looking at muscle cells before and after exercise in the fasted state, you can see that there are more muscle bundles, but also that there is a deeper shade of red, indicating more available fat for energy.
The Rationale Behind Intermittent Fasting
One of the main reasons people follow an intermittent fasting program is because of the positive metabolic and hormonal changes fasting induces that lead to improved health and fat loss.
Intermittent fasting more closely mimics the way our paleo ancestors ate. They did not have 24/7 access to food like we do today. Our ancestors would have gorged for a day or two on animal that was killed and then they would go stretches without much to eat. Plus, they were simply more active throughout the day than we are today. Going through stretches were you are not eating actually makes the body work more efficiently.
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Does Exercising While Fasting Burn More Fat
Yes, it does.63 You burn more fat if you exercise on an empty stomach.
Your body compensates for the increase in fat oxidation by storing more fat or burning less fat during the day. The result? Probably no difference compared to exercising during your eating window or soon after.
Some speculate that fasted cardio makes a difference if youre already in great shape and trying to lose the last bodyfat to get shredded. No studies confirm this, though, but many bodybuilders have found, through trial-and-error, that morning workouts work best for them when competition time draws closer.
Dont force yourself to do fasted cardio to lose body fat if you dont like it. Of course, it could also be an essential time-saver if you only have a specific time slot where you can squeeze some cardio in.
When To Work Out While Intermittent Fasting
The best time to work out while intermittent fasting is usually upon waking, or shortly after, to support the bodys natural circadian rhythm. Studies show that working out too close to bedtime can interrupt levels of deep and REM sleep, so better save exercise for the following day.
Ideally, you dont want to eat directly after a workout for the same reasons youre exercising in a fasted state: hormone optimization. Studies show that even waiting two to three hours after a workout before eating promotes a rise in growth hormone, which helps make you a fat burner and replaces the used energy . Adaptation to the stress created from a high-intensity workout is the reason a hormone shift occurs. If your schedule only permits a lunchtime workout, you can exercise in your available time, and then benefit from the hormonal boost by refraining from eating until two to three hours after exercising.
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Does Intermittent Fasting Slow Down Your Metabolism
Contrary to common myths, probably not. Meal frequency does not impact how many calories you burn.72 A calorie deficit, eating fewer calories than you expend over an extended time, slows down your metabolic rate.73However, intermittent fasting might not, at least throughout a couple of months.74 A short-term fast, up to three days, boosts your metabolic rate quite a bit.75
Unfortunately, no real long-term studies compare intermittent fasting with continuous calorie restriction. Weight loss always lowers your metabolic rate a bit, but nothing suggests that intermittent fasting is worse than regular dieting. If anything, research indicates the opposite.
Consider The Type Of Fast
If youre doing a 24-hour intermittent fast, Lippin says you should stick to low-intensity workouts such as:
- restorative yoga
- gentle Pilates
But if youre doing the 16:8 fast, much of the 16-hour fasting window is evening, sleep, and early in the day, so sticking to a certain type of exercise isnt as critical.
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What Should I Eat First Following A Fast
I recommend a high-protein meal over one loaded with carbs when coming off a fast. Work from the lab at Yale found that when you fast then refeed with a low-carb meal, the activity of the genes that boost calorie consumption and fat burning is further increased. However, when you refeed with a high-carb meal, the activity of many of these genes is decreased.
First Things First What Actually Is Intermittent Fasting
There are three main approaches I encourage people to try at The Fast 800, and they complement each other, so they can be utilised separately or together depending on your lifestyle:
- A 5:2 approach where you restrict your calorie intake to 800 kcal for two days a week and eat a healthy diet for the other five days.
- Time-Restricted Eating encourages you to extend your normal nighttime fast by eating an early dinner, or skipping breakfast, to condense your eating period into an 8-10 hour eating window each day.
- Consuming 800 kcal daily for up to 12 weeks.
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Youre Fasting Should You Work Out
- You may burn more fat.
- If fasting long term, you could slow down your metabolism.
- You might not perform as well during workouts.
- You may lose muscle mass or only be able to maintain, not build, muscle.
If youre set to try IF while continuing your exercise routine, there are some things you can do to make your workout effective.
Sprint Training And Intermittent Fasting
Sprint training or high intensity interval training involves intervals of intense activity combined with rest for about 15-30 minutes. Not only is sprint training time very efficient, but studies show that it provides health benefits that you cannot get from aerobic exercise alone, such as the tremendous boost of human growth hormone . Some of the benefits of sprint training include increased strength and stamina in the muscles and brain, increased growth hormone, improved body composition, increased brain function, higher testosterone levels, and less depression. Sprint training with intermittent fasting increase all these benefits. Sprint training is the ideal exercise method to incorporate into your fasted period, and to increase the benefits even more, you can continue to fast two to three hours post-workout.
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Is It Ok To Lift Weights On An Empty Stomach
Yes! As long as you eat after the workout, youre good to go. You dont build muscle during your training session. Muscle protein synthesis only kicks in 60-90 minutes afterward.59 If you eat some protein after your fasted workout, your muscles have everything they need when protein synthesis takes off.
Some people feel like crap or cant perform their best when exercising intensely on an empty stomach. If thats you, dont force yourself to do heavy lifting in the gym. But there is nothing inherently wrong with working out on an empty stomach.
What Are The Best Exercises On Intermittent Fasting
In this case everything depends on the intermittent fasting variation you choose. If you opt for a 16:8 diet, you can choose both strength and cardio exercises. However, if you want to try alternate day or 24-hour fasting and keep training during the fasting days, it is better to opt for less intensive workouts. Yoga and pilates will be a nice option. Walking is Ok as well.
Is Fasted Exercise Safe A Good Idea
First, lets address the controversy.
Scientists, researchers, and coaches continue to debate the merits of fasted exercise for weight loss. And scientific studies find conflicting results in that regardsuffice to say that the jury is still out .
However, for the purposes of this article, were investigating the safety and health benefits of fasted exercise.
The good news is that for most people, fasted exercise is perfectly safe.
Without a doubt, humans have always performed physical activity in the fasted state our bodies are capable of surviving and thriving during extended fasts, and our ancestors were no couch potatoes.
That said, if youre new to fasting or havent exercised in a while, you should talk to your doctor first. And if you have diabetes or low blood sugar levels, take medications, or are pregnant, definitely seek a medical opinion before you try fasted exercise.
Now, with the essential question of safety out of the way, what are the caveats to pairing up exercise with intermittent fasting?
Tips For Working Out While Intermittent Fasting
Ease into it. There is no perfect plan that works for everyone, so try building up your workouts slowly as your body adjusts to this new way of eating. “If you’re used to eating beforehand, then you do an hourlong workout in the morning, that’s going to be a lot,” Cannon says. “But if you do like a 15-minute 20-minute workout, you might be able to get away with it in transition.”
Think about what time of day you prefer to work out. If you’re someone who only works out pre-8 a.m., you may need to adjust your eating hours so you can consume a meal directly after a cardio workout. If you’re a fan of afternoon workouts, that’s a sweet spot for weight training. Low-intensity workouts can be done at any time of day.
Be flexible with your eating window. Your friend who does IF may swear by an eating window of 12 p.m. to 8 p.m., but if you love your morning runs, this won’t work as well for you. You may need to try switching to a 9 a.m. to 5 p.m. eating window so you can fit in a post-workout protein shake.
Hydrate. Just because you’re going an extended period without eating does not mean you should skimp on water! “For somebody who’s intermittent fasting, something that’s really crucial is to make sure that if they’re going to do fasted cardio, they are hydrated,” Schehr says. Try to consume at least 72 ounces of water per daymore if you’re sweating a lot.
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So What Happens During A Fast
Its just the food-storage process in reverse. First, your body burns the stored sugar, then it burns the stored fat. In essence, during feeding you store food energy. During fasting, you burn energy from your stored food .
Note that the amount of energy that is used by, and available to, your body stays the same. The basal metabolic rate stays the same. This is the basic energy used for vital organs, breathing, heart function etc. Eating does not increase basal metabolism except for the small amount used to digest food itself .
If you exercise while fasting, the body will start by burning sugar. Glycogen is a molecule composed of many sugars all put together. When it comes time to use it for energy, the liver simply starts breaking all the chains to release the individual sugar molecules that can now be used for energy.
Fasted Exercise And Performance
The effects of fasted exercise and athletic performance have been investigated in various studies utilizing different fasting and exercise protocols to mixed results. The research generally shows that fasted exercise doesnt offer a performance benefit. And studies on the effects of short-term fasting on exercise performance suggest a decrease in physical performance.
Both fasted and fed training can impact exercise metabolism in distinct ways. Exercise in a fed state shows short-term performance benefits while fasted exercise shows benefits in the longer term for metabolic adaptations.
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Exercise In Fasting Or Fed State
When you are intermittent fasting you have two choices when it comes to exercise. You can exercise during the time you are actually fasting. Or, you can exercise during your feeding window. This would be called exercising in a fed state.
There are pros and cons to exercising during the fasting phase as well as exercising during a fed state. Also, how you exercise depends on your exercise goals. Are you exercising to lose fat, exercising to gain muscle, or exercising to improve cardio fitness?
Exercise During Intermittent Fasting
Exercise during intermittent fasting will facilitate fat loss when you exercise in the fasted state. So if fat loss is your goal then try to exercise in a fasted state.
Since you have already been fasting so your insulin levels will be low. Exercising when insulin levels are low enables your body to tap into fat stores to provide calories for your workout. In other words, you are more likely to burn fat during your workouts when in a fasting state.
Plus, you set the tone to increase your metabolism for the rest of the day by exercising in a fasting state through hormonal changes enabling you to burn more fat during the remainder of the day.
Exercise in Fed State
But, that should not be a problem because your body will have enough energy stored in the blood stream and muscles to handle a more intense or longer duration exercise session.
Does Intermittent Fasting Work Without Exercise
Intermittent fasting came about independent of exercise. Much of the early anecdotal evidence and quite a lot of the clinical evidence on intermittent fasting relates primarily to IF without exercise.
People began doing intermittent fasts to restrict calorie intake and to lose weight. While this had obvious positive results, one of the important things researchers discovered was that intermittent fasting has a positive effect on the chemistry of metabolism.
Intermittent fasting can alter hormones that control metabolic rate. This leads to increased weight loss on top of the weight loss from restricted calories. It also has the benefit of long-term weight loss because the changes in metabolism remain in place even after the fasting is complete.
This last benefit has the collateral benefit of helping to control insulin and blood sugar levels. Intermittent fasting independent of exercise can help control things like type 2 diabetes.
The simple answer is yes, intermittent fasting does work even without exercise.
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