Basics of Intermittent Fasting

In the years since first learning of intermittent fasting (IF) from my doctor, IF has really gone mainstream and there are lots of recommendations, opinions and philosophies surrounding this way of eating. This post will by no means be a comprehensive look at IF, nor is it a recommendation, but I do hope to provide you with a basic outline of intermittent fasting, how it might help you and give you a little scientific evidence to its effectiveness.

Let’s start with the different versions of IF:

1. Alternate Day Fasting – There are actually several different versions of fasting that fit into this category and it may not be as straight-forward as it sounds. Some versions call for eating normally for two days, fasting for three, eating for two, fasting for three and so on. Another version of this method is fasting for 24 hours and then eating normally the next day, but in fact, you are still eating some every day. Confusing? What this might look like in practice: day 1: eat three meals, finish eating at 7 PM. day 2: fast all day until dinner at 7 (you will have fasted 24 hours). day 3: eat three meals. And so on. There is also a version that involves eating normally for two days, fasting for one day, then eating very restricted calories for the remainder of the week. That last one sounds way too complicated to me! Part of the beauty of IF is that it can simplify your life.
2. Time Restricted Feeding (which might be referred to as the 18:6 method or 19:5 or even 12:12) – the bottom line here is that you fast for the majority of the day and eat within a restricted window. Within Time Restricted Feeding, there are two variations:
   1. Skipping Breakfast – this is undeniably the most popular version of intermittent fasting and involves not eating until around lunch time. Some people enjoy coffee with a little cream or collagen, keeping the calorie count under 50. Others just drink water or herbal tea. Either way, you don’t enjoy your first real meal of the day until somewhere around 11-1.
   2. Skipping Dinner – this version was new to me, has some compelling evidence behind it and is, in my opinion, the most difficult version of fasting if you have a family. For one thing, once you begin to eat, the body releases insulin, which makes you want to eat more. So by eating early in the day and trying to fast later, you are setting yourself up to struggle. More on this below.
3. Fasting-Mimicking Diets – introduced by Dr. Valter Longo and used to treat serious diseases, including Alzheimers, Epilepsy, Parkinson’s and Cancer. You can buy kits that contain all your food, you can buy meal plans, or you can simply follow his outline with regard to calorie counts and specific macro- and micro-nutritients to consume each day. You are never fasting completely for an entire day, but the calories are restricted and it’s a very specific eating plan designed to make the body think it is fasting.

I’ll spend the majority of the space here talking about Time Restricted Feeding because it is the most common and arguably the easiest form of IF to implement. It’s also what I have been doing for two full years now and don’t think I’ll ever go back to eating all day every day.

What the research says:

There is currently a lot of research being conducted on intermittent fasting – in mice and rats. There is some research being done in humans, but not nearly enough to draw any solid, statistically-significant conclusions. We learn a lot from mice, but it’s important to remember that mice are not the same as humans.

A variety of beneficial health effects have been seen in these animal models:

• Fasting can counteract disease processes and improve functional outcomes in a wide range of age-related disorders including diabetes, cardiovascular disease, cancers and neurological disorders such as Alzheimer’s disease, Parkinson’s disease and stroke.
• One of the beneficial process we see happening inside the body during intermittent fasting is called autophagy, which sounds scary, but it’s actually a good thing and something a healthy body does normally. Autophagy is a process by which the cell (the building blocks of the body) becomes more efficient, getting rid of old, poorly-functioning parts. This is an important process for boosting immunity, protecting against autoimmunity and reducing inflammation. Autophagy only happens during fasting. This is why you’ve probably heard something along the lines of, “Your body repairs itself during sleep.” That’s because of autophagy. During IF however, autophagy can be enhanced and therein lies the benefit. 

Human studies are ongoing and results are encouraging. I don’t intend for this post to be a thorough review of the literature, but after a quick glance at articles published in the last 5 years, there seems to be enough evidence for fasting to consider it if you want to improve your general health, address serious conditions like Alzheimers disease or cancer, or lose weight and improve associated outcomes such as insulin sensitivity, joint inflammation and more.

Honestly, I wrote a similar article for my membership community a couple years ago and was thinking I would just copy and paste that article for you here, but as I dove into the research and carefully read what I wrote then, I realized that the news on IF has changed significantly since then.

Something that I believe is very important to remember is that your health is yours only. You are in charge and you are the best indicator of whether or not something is working for you. This is really key to living a functional medicine lifestyle. You need to be ok with experimentation (within limits of course) and be willing to make changes that go against mainstream medical advice. You need to be willing to keep tweaking and trying until you find what works for you. The science and medical professionals may not support what you’re doing yet, but if you know it works for you, then that’s ok!

Some possible positive effects of fasting (mostly anecdotal evidence, but the science is definitely evolving here):

• Balanced hormones – primarily we’re talking about insulin sensitivity going up (which is good), and balancing of grehlin and leptin (the so-called fullness and hunger hormones).
• Increased secretion of growth hormone which promotes fat loss. Chronically high cortisol causes the opposite effect – an increase in inflammation, which causes lean muscle breakdown and fat storage
• Extended fasting, like alternate day fasting, has been shown to help with the elimination of type 2 diabetes, metabolic syndrome and obesity
• Reduces gut inflammation, primarily by helping to balance the microbiome

I want to note that these potential benefits are HUGE and should not be discounted simply because they have not been proven in large, peer-reviewed scientific studies yet. It is very difficult to conduct such a study because there are so many complicating factors. Correlation doesn’t equal causation. Meaning, just because people following an intermittent fasting protocol see a reduction in inflammation and increase in insulin sensitivity (for instance), doesn’t mean that the fasting caused those results. But it might have. It’s very hard to know. You would have to control for so many different factors and count on the study participants being 100% compliant, which is just about nearly impossible.

Let’s loop back around to the different types of intermittent fasting for a moment. Remember, I talked about Time-Restricted Feeding being the most popular form of fasting? Most of us who practice IF extend our bedtime fast through the morning hours and begin eating mid-day. It turns out that the opposite of what most of us do, Circadian Feeding or Early Time-Restricted Feeding (skipping dinner) may show more promise with regards to real health benefits. It’s just harder to implement for some.

Eating to match the natural rise and fall of your cortisol levels has been shown to be very beneficial to the microbiome, increases fat burning and helps to reset the circadian rhythms, which is particularly beneficial if you have trouble sleeping. For most people, our cortisol rises with the sun, around 7 AM and begins to drop around 3 PM. So to match your feeding window to this rhythm, you would begin eating upon waking, eat most of your calories early in the day, say by noon, and have a light dinner around 3 or 4 PM. The old adage, “Eat breakfast like a king, lunch like a prince and dinner like a pauper” follows this line of research.

The question is: Does that sound practical or sustainable to you? Perhaps if you are someone who does shift work or if you are single and only responsible for feeding yourself, or have a very flexible family, you could make this work. Remember that there is often a big difference between ideal and practical.

What the research says about early time-restricted feeding (skipping dinner):

• A study published in 2017 showed some very negative effects of intermittent fasting when the feeding window began late in the morning (skipping breakfast): increased insulin resistance, higher blood sugar and insulin levels after eating that first meal of the day, an increase in risk of Type 2 Diabetes and cardiovascular disease. Not good!
• With other studies that looked at a time-restricted feeding window that began shortly after waking up, these results were reversed. However, there have been many studies conducted on the health benefits of sleep, exercise and stress management and the positive effects of eating from early morning until mid-afternoon and then fasting until the next morning, were far less significant than the positive effects of these other healthy lifestyle behaviors.
• There are studies showing metabolic benefits of eating breakfast as well as eating in time with your circadian rhythms. Both of these strategies should be easier to follow than some of the intermittent fasting protocols.

So where does this leave us? As with most things lifestyle intervention related, I suggest you think carefully about what works for your lifestyle and family needs and then if you want to give IF a try, give it a try for a short time (about two weeks) and see how you feel and how it affects your life.

Because so much of the positive evidence around IF is anecdotal, I’m going to share my personal experience with you in hopes that it might help you decide if some form of IF may be for you.

I began “clean” fasting two years ago. Some proponents of fasting claim that you can have cream in your coffee, a small amount of calories, maybe some collagen too, and still consider that fasting. Based on the work of Dr. Jason Fung and others, I’ve come to see that as not really fasting. A clean fast would be one where you consume only water, black tea or black coffee. Anything with flavor that would cause your body to release insulin is necessarily not a fast.

I started by fasting after dinner all the way until around 11 AM the next day. This usually equalled a 17-18 hour fast. I would then eat lunch and dinner. However, I knew that based on some existing research, many of the benefits of fasting didn’t kick in until at least 20 hours of fasting. So I began pushing my eating window back by 30 minutes every week or so. The first day I fasted all the way until 3 PM I had so much energy I thought I could run to the moon and back! That feeling was definitely motivation to keep going with this kind of fasting.

Eventually, this became my norm. Some days, I fast longer and some days shorter, just depending on what is going on with my day and how hungry I am. I have found that by my second weight lifting day of the week, I am normally more hungry and not able to fast as long. We will talk strategies for fasting longer and how to tell when you really need to eat (vs. just want to eat) in part two of this post.

Some of the benefits of fasting for me:

• Paleo eating and cooking can be time consuming. When I am only preparing one or two meals a day, it saves me a lot of time.
• Paleo eating and cooking can be expensive. Fasting means generally eating less and so there is a cost savings.
• Travel is way easier – I just need coffee in the mornings. Taking, preparing, or acquiring breakfast food for my family is easier because their diet is not as restrictive as mine.
• I am much more productive in the mornings when I don’t have to take time to prepare, eat and clean up a meal. And I get more sleep!
• Major (really huge!) health improvements, which I will discuss in a second post.

If you have tried IF and either didn’t feel well, generally didn’t like it or found it way too difficult for your busy life, there might be other ways to achieve the same health benefits that might come from IF – regular exercise (preferably outside), good stress management techniques and good sleep habits. If I could make it work with my family life, I would happily give skipping dinner a try. It does seem that the evidence suggests that form of IF to be the most beneficial. When I was a kid, I lived in Ohio near my grandparents. I LOVED spending time on their farm and managed to invite myself over just as often as I possibly could. My parents owned a busy restaurant, so in the summer, my brother and I were at the farm A LOT. My grandparents always ate breakfast and then their big meal at noon and just something “snacky” at dinner time. This was a typical menu: Breakfast: coffee with cream, eggs and toast. Lunch: meat, several vegetables and dessert (meat was local and grass-fed beef mostly, vegetables were from the garden, everything was cooked in lard or bacon fat or butter, desserts were full of butter and sugar). Dinner: small sandwich or dish of ice cream.

Now in today’s healthy eating age, most would cringe at that daily feast, but my grandparents followed a lot of the guidance listed in this review: they rose with the sun and went to bed early, they spent a lot of time outdoors, rarely sat down, ate locally and minimally processed foods, consumed the bulk of their calories early in the day and were generally stress free. My grandfather smoked for many years and dealt with some consequences of that, but both of them lived long, healthy lives. Unfortunately, I’m not a farmer and neither is my husband. I’m self-employed, but he is not, and I know this is the case for most people in our modern society. So it simply isn’t practical for most people to eat their big meal in the middle of the day. But is there a way to implement some of these principles into our busy lives? Perhaps. If you’re like me and do well with skipping breakfast, but would like to give the Circadian rhythm fasting a try, here are some ideas: 

• Add extra collagen and cream (almond, coconut, etc.) to your coffee. You could also make bulletproof coffee with butter and MCT oil. Those recipes usually yield about 300 calories.
• Eat a hearty lunch that is easy to prepare: eggs over a great big salad with nuts, avocado, healthy dressing and lots of veggies would provide plenty of nutrition and calories.
• Make dinner as usual for your family and just keep your portion small.
• Stop eating right after dinner. No snacking. At most, have herbal tea.

A couple additional tips: Breaking the fast: Start with something small at first and see how you feel. Some people report not feeling well after their first post-fast meal and it’s usually when they eat a huge meal because they’re so hungry. It may take some self-restraint, but go easy – at least initially. If you feel like IF is working for you and you want to continue, you will eventually get to the point where you are not ravenous at the end of your fast and it will be easier to consume a modest meal. How long will it take to get to that non-ravenous point? It depends on your body, but generally not very long, like 5-7 days. Our bodies are quite remarkable and they adapt quickly. If you do not have any fat to lose, but want to try fasting for other health reasons, following the fasting-mimicking plan might be a good place to start. As always, consult your personal physician (not Dr. Google) for advice specific to your body. Everything in this post is intended to be general information and not medical advice.

Come back for part two where I share the health gains I saw with fasting and strategies for how to make this work in real life. It’s one thing to talk about fasting or say you want to give it a try, but it’s another thing altogether to actually refrain from eating for an extended period of time – especially when those around you are eating. But it can be done! Stay tuned…

Citations

Aksungar FB, et al.  “Comparison of Intermittent Fasting Versus Caloric Restriction in Obese Subjects: A Two Year Follow-Up.” J Nutr Health Aging. 2017;21(6):681-685. doi: 10.1007/s12603-016-0786-y.

Ballon A, et al. “Breakfast Skipping Is Associated with Increased Risk of Type 2 Diabetes among Adults: A Systematic Review and Meta-Analysis of Prospective Cohort Studies.” J Nutr. 2019 Jan 1;149(1):106-113. doi: 10.1093/jn/nxy194.

Farshchi HR, et al. “Deleterious effects of omitting breakfast on insulin sensitivity and fasting lipid profiles in healthy lean women.” Am J Clin Nutr. 2005 Feb;81(2):388-96.

Hatori M, et al. “Time-restricted feeding without reducing caloric intake prevents metabolic diseases in mice fed a high-fat diet.” Cell Metab. 2012 Jun 6;15(6):848-60. doi: 10.1016/j.cmet.2012.04.019. Epub 2012 May 17.

Horne BD, et al. “Health effects of intermittent fasting: hormesis or harm? A systematic review.” Am J Clin Nutr. 2015 Aug;102(2):464-70. doi: 10.3945/ajcn.115.109553.

Jakubowicz D, et al. “Effects of caloric intake timing on insulin resistance and hyperandrogenism in lean women with polycystic ovary syndrome.” Clin Sci (Lond). 2013 Nov;125(9):423-32. doi: 10.1042/CS20130071.

Jakubowicz D, et al. “Fasting until noon triggers increased postprandial hyperglycemia and impaired insulin response after lunch and dinner in individuals with type 2 diabetes: a randomized clinical trial.” Diabetes Care. 2015 Oct;38(10):1820-6. doi: 10.2337/dc15-0761. Epub 2015 Jul 28.

Jakubowicz D, et al. “High caloric intake at breakfast vs. dinner differentially influences weight loss of overweight and obese women.” Obesity (Silver Spring). 2013 Dec;21(12):2504-12. doi: 10.1002/oby.20460. Epub 2013 Jul 2.

Jamshed H, et al. “Early Time-Restricted Feeding Improves 24-Hour Glucose Levels and Affects Markers of the Circadian Clock, Aging, and Autophagy in Humans.” Nutrients. 2019 May 30;11(6). pii: E1234. doi: 10.3390/nu11061234.

Ofori-Asenso R, et al. “Skipping Breakfast and the Risk of Cardiovascular Disease and Death: A Systematic Review of Prospective Cohort Studies in Primary Prevention Settings.” J Cardiovasc Dev Dis. 2019 Aug 22;6(3). pii: E30. doi: 10.3390/jcdd6030030.

Melkani GC and Panda S. “Time-restricted feeding for prevention and treatment of cardiometabolic disorders.” J Physiol. 2017 Jun 15;595(12):3691-3700. doi: 10.1113/JP273094. Epub 2017 Apr 25.

Moro T, et al.”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.” J Transl Med. 2016 Oct 13;14(1):290.

Nas A, et al. “Impact of breakfast skipping compared with dinner skipping on regulation of energy balance and metabolic risk.” Am J Clin Nutr. 2017 Jun;105(6):1351-1361. doi: 10.3945/ajcn.116.151332. Epub 2017 May 10.

Patterson, RE, et al. “Intermittent Fasting and Human Metabolic Health“. J Acad Nutr Diet. 2015 Aug; 115(8): 1203–1212. Published online 2015 Apr 6. doi: 10.1016/j.jand.2015.02.018

Ravussin E, et al. “Early Time-Restricted Feeding Reduces Appetite and Increases Fat Oxidation But Does Not Affect Energy Expenditure in Humans.” Obesity (Silver Spring). 2019 Aug;27(8):1244-1254. doi: 10.1002/oby.22518.

Sutton EF, et al. “Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes.” Cell Metab. 2018 Jun 5;27(6):1212-1221.e3. doi: 10.1016/j.cmet.2018.04.010. Epub 2018 May 10.

Zarrinpar A, et al. “Diet and feeding pattern affect the diurnal dynamics of the gut microbiome.” Cell Metab. 2014 Dec 2;20(6):1006-17. doi: 10.1016/j.cmet.2014.11.008.