It’s a debate that’s raged since the first weight was lifted: Is it better or worse to work out on an empty stomach? Wars have been waged and nations have fallen (okay, that’s a slight exaggeration) during the eternal battle of fed versus fasted exercise, but it’s time for this madness to end. We have the final answer.
It's time to dismantle some old myths about eating and exercise.
Well, not the final answer. Different people work out best under different circumstances, and deciding whether someone should eat before training can be like telling them what time of day to work out or which diet they should follow—it largely depends on what works best for the individual. But it is time to dismantle some old myths.[AD]
Contrary to popular belief, research suggests that eating many small meals throughout the day won’t speed up the metabolism, skipping a meal won’t make you fat, and exercising on an empty stomach will not nullify a workout. In fact, skipping a meal or two, also known as “intermittent fasting” (IF), can be downright beneficial.
Optimizing Hormones (Fast)
If the fact that Huge Jacked-man practiced intermittent fasting to gain muscle for his latest Wolverine movie isn’t convincing enough, consider this: An empty stomach triggers a cascade of hormonal changes throughout the body that are surprisingly conducive to both building muscle and burning fat.
An empty stomach triggers a cascade of hormonal changes throughout the body that are conducive to both building muscle and burning fat.
The fasted state produces two significant effects:
1. Improved insulin sensitivity. Put very simply, the body releases insulin (a hormone) when we eat to help us absorb the nutrients from our food. The hormone then takes the sugars out of our bloodstream and directs them to the liver, muscles, and fat cells to be used as energy later on. The trouble is that eating too much and too often can make us more resistant to insulin’s effects, and while poor insulin sensitivity ups the risk of heart disease and cancer, it also makes it harder to lose body fatInsulin, glucose, insulin resistance, and pancreatic cancer in male smokers. Stolzenberg-Solomon RZ, Graubard BI, et al. National Cancer Institute, Department of Health and Human Services, Rockville, MD, USA. Journal of the American Medical Association, 2005 Dec 14;294(22):2872-8. Effect of intermittent fasting and refeeding on insulin action in healthy men. Halberg N, Henriksen M, et al. Dept. of Muscle Research Centre, The Panum Institute, University of Copenhagen, Denmark. Journal of Applied Physiology, 2005 Dec;99(6):2128-36 The correlation between metabolic syndrome and prostatic diseases. De Nunzio C, Aronson W, et al. Department of Urology, Sant'Andrea Hospital, University La Sapienza, Rome, Italy. European Urology, 2012 Mar;61(3):560-70 Insulin resistance and breast-cancer risk. Bruning PF, Bonfrèr JM, et al. The Netherlands Cancer Institute, Amsterdam, The Netherlands. Bruning PF, Bonfrèr JM, et al. The Netherlands Cancer Institute, Amsterdam, The Netherlands. International Journal of Cancer, 1992 Oct 21;52(4):511-6 Insulin resistance and cancer: epidemiological evidence. Tsugane S, Inoue M. Cancer Science, 2010 May;101(5):1073-9.. Eating less frequently (i.e. fasting more regularly) is one way to help remedy the issue, because it results in the body releasing insulin less often, so we become more sensitive to it—and that makes it easier to lose fat, improves blood flow to muscles, and even curbs the impact of an unhealthy diet Effect of intermittent fasting and refeeding on insulin action in healthy men. Halberg N, Henriksen M, et al. Dept. of Muscle Research Centre, The Panum Institute, University of Copenhagen, Denmark. Journal of Applied Physiology, 2005 Dec;99(6):2128-36. Usefulness of routine periodic fasting to lower risk of coronary artery disease in patients undergoing coronary angiography. Horne BD, May HT, et al. Cardiovascular Department, Intermountain Medical Center, Murray, Utah, USA. American Journal of Cardiology, 2008 Oct 1;102(7):814-819..
2. The second reason a good old-fashioned fast can promote muscle gain and fat loss comes down to growth hormone (GH), a magical elixir of a hormone that helps the body make new muscle tissue, burn fat, and improve bone quality, physical function, and longevity Growth hormone increases muscle mass and strength but does not rejuvenate myofibrillar protein synthesis in healthy subjects over 60 years old. Welle S, Thornton C, et al. The Journal of Clinical Endocrinology and Metabolism, 1996 Sep;81(9):3239-43. Growth hormone in health and disease: Long-term GH therapy--benefits and unanswered questions. Clemmons D. Nature Reviews Endocrinology, 2013 Jun;9(6):317-8 Adult growth hormone deficiency - benefits, side effects, and risks of growth hormone replacement. Reed ML, Merriam GR. Geriatrics and Extended Care, VA Puget Sound Health Care System, Madigan Health Care System, Tacoma, WA, USA. Frontiers in Endocrinology (Lausanne), 2013 Jun 4;4:64. Basal growth hormone concentration increased following a weight loss focused dietary intervention in older overweight and obese women. Miller GD, Nicklas BJ, et al. Department Health and Exercise Science, Wake Forest University, Winston-Salem, NC, USA. The Journal of Nutrition Health and Aging, 2012 Feb;16(2):169-74.. Along with regular weight training and proper sleep, fasting is one of the best ways to increase the body’s GH: One study showed that 24 hours without food increases the male body’s GH production by 2,000 freakin'percent, and 1,300 percent in women. The effect ends when the fast does, which is a compelling reason to fast regularly in order to keep muscle-friendly hormones at their highest levels.
We can’t speak of muscle-friendly hormones without bringing up testosterone. Testosterone helps increase muscle mass and reduce body fat while also improving energy levels, boosting libido, and even combating depression and heart problems—in both men and women Sex differences in anxiety and depression: Role of testosterone. McHenry J, Carrier N, et al. Frontiers in Neuroendocrinology, 2014 Jan;35(1):42-57. Beneficial and adverse effects of testosterone on the cardiovascular system in men. Ruige JB, Ouwens DM, et al. Journal of Clinical Endocrinology and Metabolism, 2013 Nov;98(11):4300-10. Andropause or male menopause? Rationale for testosterone replacement therapy in older men with low testosterone levels. Cunningham GR. Endocrine Practice, 2013 Sep-Oct;19(5):847-52. Effects of testosterone and progressive resistance exercise in healthy, highly functioning older men with low-normal testosterone levels. Hildreth KL, Barry DW, et al. The Journal of Clinical Endocrinology and Metabolism, 2013 May;98(5):1891-900.. Fasting alone may not have any effect on testosterone, but there is a surprisingly simple way to produce large amounts of both “T” and growth hormone at the same time, creating an optimal environment for building muscle and torching fat: Exercising while fasted Effects of Ramadan fasting on 60 min of endurance running performance in moderately trained men. Aziz AR, Wahid MF, et al. British Journal of Sports Medicine, 2010 Jun;44(7):516-21..
The Fast Way to Improve Performance
Exercise, especially intense exercise that uses a lot of muscles (think compound movements like deadlifts and squats) causes a big surge in testosterone—which is why it can make good sense to combine exercise and fasting Hormonal responses and adaptations to resistance exercise and training. Kraemer WJ, Ratamess NA. Sports Medicine, 2005;35(4):339-61. Testosterone physiology in resistance exercise and training: the up-stream regulatory elements. Vingren JL, Kraemer WJ, et al. Sports Medicine, 2010 Dec 1;40(12):1037-53.. Many studies have found that training in a fasted state is a terrific way to build lean mass and boost insulin sensitivity, not just because of the nifty hormonal responses, but also because it makes the body absorb the post-workout meal more efficiently.
Many studies have found that training in a fasted state is a terrific way to build lean mass and boost insulin sensitivity.
In short, fasted training helps to ensure that carbs, protein, and fats go to the right places in the body and are stored only minimally as body fat Exercise in the fasted state facilitates fibre type-specific intramyocellular lipid breakdown and stimulates glycogen resynthesis in humans. De Bock K, Richter EA, et al. Journal of Physiology2005 Apr 15;564(Pt 2):649-60. Increased p70s6k phosphorylation during intake of a protein-carbohydrate drink following resistance exercise in the fasted state. Deldicque L, De Bock K, et al. European Journal of Applied Physiology, 2010 Mar;108(4):791-800. Metabolic responses to exercise after fasting. Dohm GL, Beeker RT, et al. Journal of Applied Physiology, 1986 Oct;61(4):1363-8 Alternate-day fasting in nonobese subjects: effects on body weight, body composition, and energy metabolism. Heilbronn LK, Smith SR, et al. American Journal of Clinical Nutrition, 2005 Jan;81(1):69-73. Training in the fasted state facilitates re-activation of eEF2 activity during recovery from endurance exercise. Van Proeyen K, De Bock K, et al. European Journal of Applied Physiology, 2011 Jul;111(7):1297-305.. Exercising on an empty stomach has been shown to be especially great for fat loss, and it’s even been shown that people who train while fasted become progressively better at burning fat at higher levels of intensity (possibly because of an increase in fat-oxidizing enzymes) Training in the fasted state improves glucose tolerance during fat-rich diet. Van Proeyen K, Szlufcik K, et al. 2010 Nov 1;588(Pt 21):4289-302. Effect of training in the fasted state on metabolic responses during exercise with carbohydrate intake. De Bock K, Derave W, et al. Journal of Applied Physiology, 2008 Apr;104(4):1045-55..
Not interested in training like a bodybuilder? There are also potential benefits for endurance athletes, since fasted workouts can improve muscle glycogen storage efficiency (say that three times fast!) Effects of caloric restriction and overnight fasting on cycling endurance performance. Ferguson LM, Rossi KA, et al. Ferguson LM, Rossi KA, et al. Journal of Strength and Conditioning Research, 2009 Mar;23(2):560-70.. What that means, basically, is that running on empty can make the body better at using its energy stores. The occasional fasted training session can improve the quality of “fed” workouts (or races) later on. In a nutshell: When the body learns to exert itself without any food, it gets better at performing when it does have fuel in the tank. Some studies have also shown that fasted workouts can significantly improve endurance athletes’ VO2 Max, which measures a person’s capacity to take in and use oxygen during exercise and is a pretty decent way of measuring someone’s fitness Adaptations to skeletal muscle with endurance exercise training in the acutely fed versus overnight-fasted state. Stannard SR, Buckley AJ, et al. Journal of Science and Medicine in Sport, 2010 Jul;13(4):465-9. Beneficial metabolic adaptations due to endurance exercise training in the fasted state. Van Proeyen K, Szlufcik K, et al. Journal of Applied Physiology, 2011 Jan;110(1):236-45. Effects of caloric restriction and overnight fasting on cycling endurance performance. Ferguson LM, Rossi KA, et al. Ferguson LM, Rossi KA, et al. Journal of Strength and Conditioning Research, 2009 Mar;23(2):560-70. Using molecular classification to predict gains in maximal aerobic capacity following endurance exercise training in humans. Timmons, J.A., Knudsen, S., Rankinen, T., et al. Panum Institutet and Center for Healthy Ageing, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark. Journal of Applied Physiology, 2010 Jun;108(6):1487-96. Epub 2010 Feb 4.
When the body learns to exert itself without any food, it gets better at performing when it does have fuel in the tank.
Now, we would be remiss if we didn’t acknowledge that some studies have shown impaired performance as a result of fasted exercise. That said, many of these studies are of Ramadan fasts, which don’t allow the consumption of fluids (which is not advisable when engaging in athletic activities) Effects of Ramadan fasting on 60 min of endurance running performance in moderately trained men. Aziz AR, Wahid MF, et al. British Journal of Sports Medicine, 2010 Jun;44(7):516-21. The effect of ramadan fasting on physical performances, mood state and perceived exertion in young footballers. Chtourou H, Hammouda O, et al. Asian Journal of Sports Medicine, 2011 Sep;2(3):177-85. Ramadan fastings effect on plasma leptin, adiponectin concentrations, and body composition in trained young men. Bouhlel E, Denguezli M, et al. International Journal of Sport Nutrition and Exercise Metabolism, 2008 Dec;18(6):617-27.. Still, the prevalence of people who do eat before exercise is pretty good evidence that exercising after eating can work. Heck, there are even studies showing that eating before exercise can lead to fewer calories consumed throughout the day Effect of carbohydrate ingestion during exercise on post-exercise substrate oxidation and energy intake. Melby CL, Osterberg KL, et al. International Journal of Sport Nutrition and Exercise Metabolism, 2002 Sep;12(3):294-309.. But that doesn’t discredit the evidence that fasted workouts, even if occasional, can reap a lot of benefits.
So You Want to Fast Before Exercise? Your Action Plan
We know what you’re thinking. “I can’t handle intense exercise without food in my belly!” Firstly, give yourself a little credit! You’re capable of more than you think with the right frame of mind. Secondly, there are several tips you can follow to help you out with this new approach to eating:
- You can consume more than just water. Feel free to quell cravings and get an energy boost with black coffee, plain tea, caffeine pills, Branched Chain Amino Acids, creatine, or any kind of drink or supplement that’s virtually calorie-free. According to the leading experts on the subject, Brad Pilon and Martin Berkhan, even Diet Coke or sugar-free gum won’t break the fast.
- Break your fast whenever you'd like. A lot of people like their first meal right after exercising, since the fast improves the absorption of the post-workout meal, but it’s actually no big deal if the fast lasts for a while longer. Even if you exercise in the morning and don’t eat until the evening, the wave of growth hormone you’ll be riding all day should prevent any muscle loss The protein-retaining effects of growth hormone during fasting involve inhibition of muscle-protein breakdown. Nørrelund H, Nair KS, et al. Diabetes. 2001 Jan;50(1):96-104.. However you decide to approach this, your body’s got you covered.
- Eat as many meals as you'd like. Note: We didn't say as many calories as you like. But it’s not necessary to eat many meals throughout the day. Despite some long-held myths that the body can only absorb a certain amount of protein at a time, we're completely capable of digesting the day's intake in one big meal (of course, this doesn’t mean that you need to!). Studies have shown that doing so results in no strength or muscle loss, and some have even shown that concentrating food intake into one or two meals each day can be a better way to build lean muscle mass Intermittent fasting does not affect whole-body glucose, lipid, or protein metabolism. Soeters MR, Lammers NM, et al. American Journal of Clinical Nutrition, 2009 Nov;90(5):1244-51. Protein feeding pattern does not affect protein retention in young women. Arnal MA, Mosoni L, et al. Journal of Nutrition, 2000 Jul;130(7):1700-4. A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults. Stote KS, Baer DJ, et al. American Journal of Clinical Nutrition, 2007 Apr;85(4):981-8. Protein pulse feeding improves protein retention in elderly women. Arnal MA, Mosoni L, et al. American Journal of Clinical Nutrition, 1999 Jun;69(6):1202-8.. A lot of protein just takes longer to digest and be utilized, but it still gets digested. Even after eating a normal-sized meal, amino acids are still being released into the bloodstream and absorbed into the muscles five hours after eating Splanchnic and leg substrate exchange after ingestion of a natural mixed meal in humans. Capaldo B, Gastaldelli A, et al. Diabetes. 1999 May;48(5):958-66.. So play around with the feeding times and styles that work best for you.
The short of it: Metabolism and the digestive system are simply not as temperamental as some might believe.
Eating is perhaps the most ingrained habit we have, and humans are well and truly creatures of habit. Disrupting that habit by skipping a meal or two can be profoundly difficult for some people (particularly those who have wrestled with disordered eating). It’s true that intermittent fasting takes some getting used to as the body learns not to expect food so frequently. That discomfort usually does pass, but if fasting just isn’t for you, then there’s no need to keep it up—just don’t be afraid to try it out. IF is just one approach to health and fitness, and certainly not the only one that can get you results.
If fasting just isn’t for you, then there’s no need to keep it up—just don’t be afraid to try it out.
But myths and misconceptions do need to be dispelled, and this article is here to say this: In general, there is no need to eat before exercise. If you feel better when you do, then by all means, keep it up! However if choking down a pre-workout banana or bowl of oatmeal is a dreary chore that you only do because it’s supposed to help you avoid muscle loss/fat gain/growing antlers, then it’s time to relax. You’re completely free to eat whenever you want. Just listen to your body—it’s got you taken care of.