What is intermittent fasting?
Intermittent fasting in its simplest form is going without food for intermittent periods and eating during other periods. One of the most popular methods of intermittent fasting involves eating all of your day’s food within an 8 hour window. The easiest way to do this? Skip breakfast.
Wait what? The most important meal of the day?!
Let’s take a look at some of the evidence against this widely held belief:
- A 2014 study of 283 participants found no significant difference in weight when eating or skipping breakfast over a 16 week period. 1
- A review published in 2016 stated that ‘Intervention studies have generally found a reduction in total daily energy intake when breakfast is omitted from the daily meal pattern’ – contrary to the belief that skipping breakfast causes us to eat more calories during the day. 2
- A study published in Physiology & Behaviour reported ‘skipping a meal does not result in accurate energy compensation at subsequent meals… skipping breakfast may be an effective means to reduce daily energy intake in some adults.’ 3
- An opinion paper published in ‘Frontiers in Public Health’ looked at 44 scientific papers and cited many studies that contradict this popular belief, concluding in fact that ‘it is reasonable to suppose that skipping breakfast could be as metabolically beneficial as excluding late eating, as well as stress the importance of the overnight fast. Perhaps it does not matter which of the daily meals – the first or the last – is omitted as long as at least once in a while, an inter-meal interval is long enough to allow the state of ketosis to initiate lipolysis and lower calorie intake, thus decreasing the risk of obesity and its comorbidities.’ 4
- Furthermore, a large Japanese study of health care claims showed that self-reported breakfast skippers had a lower incidence of all diseases (including metabolic diseases) as compared to breakfast eaters. 5
Interesting right? The truth is that over the vast majority of our existence, humans have regularly experienced periods without food. We haven’t always had the privilege of a supermarket across the road making access to food (and many highly processed foods) readily available. Dieting organisations have even suggested that we should never allow ourselves to feel hungry and rather eat up to six small meals per day so that we don’t binge on high calorie foods to fill the uncomfortable void. But given our evolution, this approach just doesn’t match our digestive and metabolic physiology.
So, should we go without sometimes?
Potential benefits of intermittent fasting
- Weight loss and improved fat burning 6, 7
- Reduced oxidative stress (oxidative stress is an imbalance between free radicals and antioxidants which can contribute to diabetes, hardening of the arteries, high blood pressure, heart disease, degenerative brain disease and cancer.) 8
- Improved lipid profile and reduced heart disease risk – reduced cholesterol, improved liver markers and reduced triglycerides 10, reduced LDL particle size 11
- Improved blood glucose levels and insulin sensitivity 12
- Reduced inflammation 13
- Improved treatment of cancer 14
- Reduced risk of breast cancer 15
- Boosts in growth hormone levels 16 (important for maintaining muscle and even bone mass, particularly as we age)
- May improve immune function and alter the gut microbiome 17
My experience
Personally I have been intermittent fasting for years, not that I previously called it that. A few times per week I would get up and get going, only to realise hours later that I hadn’t eaten anything. Or I would simply wait until I was really hungry before eating my first meal of the day. Being a yoga practitioner, I like the mental and ethical aspects of fasting. Fasting has formed an important part of many religious and spiritual systems for a long time. Lent and Ramadan are two clear examples. For me, ‘going without’ reminds me of the value of food and that not every body has a choice when it comes to being hungry. There’s something very cleansing about the lightness of fasting. There’s also something very primal about the growl that comes from your stomach and the natural urge to fill it. It really clears your mind and creates perspective, reducing the haze of less important ‘stuff’ we fill our days with. Internally, our gastrointestinal system gets a rest and our stomach acid starts to flow, ready to properly digest our next meal when it comes. Perhaps none of that is particularly intriguing to you… in which case read the previous paragraph again!
But I’m trying to build muscle!
Luckily protective mechanisms within the body work to preserve our protein and muscle stores during short term fasts. Our body first uses carbohydrates for fuel and then switches to burning fat. In fact as mentioned above, intermittent fasting actually boosts growth hormone levels helping you to maintain lean mass. 16 Furthermore, ‘an increase in nor-adrenalin will pump you up to train harder’ says Dr Jason Fung… a natural pre-workout perhaps?!
Who shouldn’t fast
There may be some good reasons why you shouldn’t fast. More obvious situations include pregnancy, breastfeeding and mental health conditions such as anorexia nervosa. If your relationship with food is poor, if your diet is terrible (no point skipping a meal then feasting on McDonalds for 8 hours) and if you are seriously stressed out and physically run down then fasting may not be your friend either. Fasting is essentially stress.
The aim of the game
Fasting is about re-setting your system – which includes your appetite. Fasting helps regulate our appetite and enables us to actually become hungry before eating. Of course a good diet is crucial to reaping the potential benefits of fasting and combining your efforts with regular exercise will deliver the best results.
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References
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Am J Clin Nutr. 2014 Aug;100(2):507-13. doi: 10.3945/ajcn.114.089573. Epub 2014 Jun 4.
The effectiveness of breakfast recommendations on weight loss: a randomized controlled trial.
Dhurandhar EJ1, Dawson J1, Alcorn A1, Larsen LH1, Thomas EA1, Cardel M1, Bourland AC1, Astrup A1, St-Onge MP1, Hill JO1, Apovian CM1, Shikany JM1, Allison DB1. -
Proc Nutr Soc. 2016 Aug;75(3):319-27. doi: 10.1017/S0029665115004243. Epub 2015 Dec 14.
The effect of breakfast on appetite regulation, energy balance and exercise performance.
Clayton DJ1, James LJ1. -
Physiol Behav. 2013 Jul 2;119:9-16. doi: 10.1016/j.physbeh.2013.05.006. Epub 2013 May 11.
Effect of skipping breakfast on subsequent energy intake.
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Front Public Health. 2014; 2: 59.Published online 2014 Jun 3. doi: 10.3389/fpubh.2014.00059PMCID: PMC4042085PMID: 24918099
Breakfast: To Skip or Not to Skip?
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Okamoto E, Hiratsuka Y, Otsubo K, Kumakawa T. Evaluation of the health check up and guidance program through linkage with health insurance claims. J Natl Inst Public Health (2013) 62(1):13–30
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JBI Database System Rev Implement Rep. 2018 Feb;16(2):507-547. doi: 10.11124/JBISRIR-2016-003248.
Intermittent fasting interventions for treatment of overweight and obesity in adults: a systematic review and meta-analysis.
Harris L1, Hamilton S2,3, Azevedo LB2,3, Olajide J2,3, De Brún C2,3, Waller G2,3, Whittaker V2,3, Sharp T4, Lean M1, Hankey C1, Ells L1,3. -
Int J Obes (Lond). 2015 May;39(5):727-33. doi: 10.1038/ijo.2014.214. Epub 2014 Dec 26.
Fasting for weight loss: an effective strategy or latest dieting trend?
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PLoS One. 2012;7(10):e47079. doi: 10.1371/journal.pone.0047079. Epub 2012 Oct 5.
Effect of modest caloric restriction on oxidative stress in women, a randomized trial.
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Obesity (Silver Spring). 2008 Jun;16(6):1355-62. doi: 10.1038/oby.2008.201. Epub 2008 Apr 10.
Effect of 6-month calorie restriction and exercise on serum and liver lipids and markers of liver function.
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Comparison of effects of diet versus exercise weight loss regimens on LDL and HDL particle size in obese adults
Lipids Health Dis. 2011; 10: 119.
Published online 2011 Jul 18. doi: 10.1186/1476-511X-10-119PMCID: PMC3150311PMID: 21767400 -
Short-term modified alternate-day fasting: a novel dietary strategy for weight loss and cardioprotection in obese adults
The American Journal of Clinical Nutrition, Volume 90, Issue 5, 1 November 2009, Pages 1138–1143, https://doi.org/10.3945/ajcn.2009.28380Lipids Health Dis. 2011; 10: 119.
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Free Radic Biol Med. 2007 Mar 1;42(5):665-74. Epub 2006 Dec 14.Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma.
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J Transl Med. 2016 Oct 13;14(1):290.Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males.
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