Sardine Fasting

What is a Sardine Fast?

Fasting is all the rage in certain health circles.  Of course, in its most basic form, fasting is just not eating, but there are also quite a few variations wherein you still eat something, but less than usual.  These include bone-broth fasting, egg fasting, and, of course, sardine fasting.

A sardine fast is not a fast from sardines, but a fast where you eat nothing but sardines (or sardines and pure fat, as we will see).  Dr. Boz has been a big proponent of the benefits of sardine fasting for a while, and Nick Norwitz recently did a sardine fast self-experiment that sounded intriguing enough that I decided to give it a try.

Why Would You Try a Sardine Fast?

Nick Norwitz explains the potential benefits of sardine fasting better than I do, so check out his video (linked above). But here is my cliffnotes version:

All the fasting variations (sardine fasting, egg fasting, bone-broth fasting, fat fasting – Kelly Hogan gives a good run-down), manage to mimic some of the benefits of a real fast, while also minimizing the downsides.  They are all very low-carb, putting the body into deep ketosis, which is one of the known benefits of fasting.  They all will lead to you just plain eating less food for the duration of the fast, which will help with rapid weight-loss and increased autophagy (albeit less autophagy than in a real fast). 

Even if you are eating fairly high-protein foods (such as eggs or sardines), the fact that you are eating relatively small quantities (try eating 150 grams of protein a day from just eggs or sardines – it’s not easy) means your total protein intake will probably be significantly lower than usual – which could upregulate the hormone FGF-21, increasing metabolism and fat-burning.  

However, because you are eating some food, you avoid some of the potential side-effects and risks of fasting, especially extended fasting.   Eating some food, especially very nutrient-dense food such as eggs or sardines, makes it less likely that you will experience lightheadedness, electrolyte imbalances, or disturbed sleep.  Furthermore, if you are fasting for several days or longer, having at least some intake of high-quality protein, even if less than usual, can help keep you from experiencing muscle-loss.  

Nick Norwitz suggests some benefits to sardines in particular:

• The protein in sardines is very high-quality and bioavailable, and contains a very high level of creatine, helping prevent muscle loss.

• Because sardines are a whole organism (minus the head, usually), they contain organs and bones and therefore have very high levels of micronutrients (including B-vitamins and calcium), giving you more “nutrition bang” for your “calorie buck”.

• Sardines have very high levels of healthy omega-3 fats, helping increase ketone levels and decrease inflammation.

• As small fish which are wild-caught and low on the food chain, sardines are among the cleanest fish you can eat in terms of pollutants and heavy metals.  

My Sardine Fast Experiment

I decided to try a three-day sardine fast as an experiment. I have done 36-hour water fasts quite a few times successfully, but have discovered, when I tried a full 72-hour water fast, that my sleep was disturbed and I got insomnia 48 hours in, even though I otherwise felt fine.  My hope was that the sardine fast would give me some of the benefits of a 72-hour water fast (rapid fat loss, lower fasting glucose, increased physical and mental energy, increased autophagy) without the sleep disruption.  

For my sardine fast experiment, I decided to follow Nick Norwitz’s protocol: eat one tin of sardines a day per 50 pounds of lean body mass, plus pure fat (olive oil, coconut oil, butter) as needed to keep energy steady.  Since I weigh about 155 pounds total (and I don’t have an exact body fat percentage, but my guestimate is I’m around 18% body fat), that would be around two and a half tins a day.

Nick didn’t give a specification about an eating window, but I figured that since I usually only eat twice a day and stick with an eight-hour window anyway, I certainly wouldn’t eat more frequently than that.  

Also, I would still eat sea-salt, and drink water and pure black coffee as desired.  

How My Sardine Fast Went

I ate my last normal meal Tuesday night, then launched into my fast on Wednesday.  

Wednesday: I did a normal workout fasted in the morning, and decided I wouldn’t eat until I got really hungry. I had a scoop of homemade, unsweetened electrolytes in my water after my workout.   At 3:30 p.m., I broke my fast with a tin of sardines, mustard, and 2 tbs of pure olive oil.  At 6:00 p.m., I ate my dinner – a tin and a half of sardines, mustard, 1 tbs olive oil, 1 tbs coconut oil, and 1 tbs butter.   I did use sardines packed with mustard and hot sauce, which technically added a few grams of carbohydrate – sorry for you purists out there.   Total macronutrients for the day:  35 grams of protein, 102 grams of fat, 5 grams of carbohydrate, 1,078 calories.

Thursday: I did a normal workout in the morning, followed by a scoop of electrolytes.  Around lunchtime, I had a tablespoon of raw apple cider vinegar in my water, both for culinary interest and to get some fermented food in my gut, since I wasn’t having my usual sauerkraut, kefir, and yogurt.  I ate one meal at 4:50 p.m. – I didn’t love eating the sardines on Wednesday, and they certainly didn’t seem any more appealing now, so I tried frying a tin and a half in a pan with bacon fat and butter and topping with mustard.  It helped a little, but they were still kind of gross.  I had another un-fried tin, as well as 2 tbs olive oil and 2 ½ tbs butter.  Total macronutrients for the day: 35 grams of protein, 105 grams of fat, 5 grams of carbohydrate, 1,105 calories.

Friday:  I did a normal workout in the morning.  Before my workout, I put a couple tablespoons of raw sauerkraut juice in my water, to give me some microbes and some salt.  At this point, the thought of more sardines made me want to retch, and I thought I would honestly enjoy water fasting more than eating more sardines.  So I water-fasted until dinnertime (6:45 p.m.), at which point my 72-hours were just about up (Tuesday night to Friday night), at which point a broke my sardine fast with some non-sardine foods – four eggs poached in crushed tomatoes, half a cup of kefir, half an avocado, two squares of 100% dark chocolate, and 8 oz of mozzarella cheese.  It tasted really good.  Total macronutrients for the day: 76 grams of protein, 94 grams of fat, 34 grams of carbohydrate, 1,286 calories.

I physically and mentally felt good throughout the three days, my workouts were just as good as normal, and my sleep was fine (so I did successfully avoid that pitfall).  My weight dropped from 156.6 to 153 pounds even over three days (I did gain about two of those pounds back over the next few weeks).  Starting about day two, my fasting glucose dropped about ten points, and consistently stayed lower for a day or two after I started eating normally again.

So, overall, it did everything I wanted it to do.  The one problem was that I didn’t like sardines when I started, and detested them by the end.  A friend suggested I might have liked them better if I paid more for higher-quality sardines – which may be true for all I know, but I also didn’t want to pay more.  Which got my thinking about trying the experiment again with eggs (which I love) instead of sardines.  Which is a topic for another blogpost… 

Should I Try Sardine Fasting?

Obviously, check with your doctor before making any radical changes to your diet, especially if you have any medical conditions or are taking any medications (I would be especially careful if you are taking any diabetic or glucose-lowering medications, as sardine fasting could make your glucose drop too low and give you hypoglycemia if you’re not careful, or on blood-thinners, as fish oil can have a natural blood-thinning effect).  

Having said that, sardine fasting is pretty safe.  I mean, all it is is going a few days eating less (not no) food – and very nutrient-dense and healthy food at that.  Here are some particular situations where it could be helpful:

• To break a weight-loss stall.

• To achieve a deeper level of ketosis for cognitive performance.

• You want to get some of the benefits of a water fast, but want to ease yourself in or can’t do a full water fast for some reason (like what happened to me with insomnia, or you have concerns about losing muscle mass).

• To help lower stubborn blood sugar which won’t come down any other way.

Sardine Fasting Tips

As with any form of fasting, check with your doctor or other relevant medical personnel first, and see how you feel.  Even though it has health benefits, significant calorie restriction is in fact a stressor on your body.  I wouldn’t recommend any form of significant calorie-restriction when you are already under extra stress, including emotional stress and severe sleep deprivation.  Try sardine fasting when you are already feeling well-rested, not run-down and exhausted.

And, of course, if it doesn’t sit well with you – if you feel sick or lightheaded – stop!  Eat a little more food and start easing back into a normal eating pattern.

How long can you sardine fast for?  I did three days, and that went well, but if you have never done something like this before, I would start with just one day and slowly build up to longer.  You certainly could do it for significantly longer than three days, but at that point, you need to seriously ask yourself what your goals are.  I don’t generally advocate for long extended fasting (longer than 3-5 days), certainly not without close medical supervision, and I wouldn’t recommend sardine fasting for longer than that – certainly not if you are maintaining a significant caloric deficit while you are doing it.  

If you water fast (or sardine fast) for three days or more, reintroduce normal food slowly to avoid making yourself sick or possibly getting a very serious condition called “refeed syndrome”.  Break your fast with something small (like two eggs), wait a few hours, and then have a normal meal – don’t stuff yourself. 

Have salt and other electrolytes liberally while sardine fasting, and drink water to thirst (you may find you naturally need to drink more water than usual to avoid getting dehydrated).  You can drink unsweetened tea or black coffee, but just beware of overdoing caffeine – if you are already someone who finds that fasting makes you sleepless or jittery, caffeine can make this worse.  

To Conclude…

Sardine fasting is a great tool to have in your toolchest.  Is it magic?  No.  Can you be perfectly happy and healthy without doing it?  Of course.  Yet, it is also a simple and powerful way to get a lot of fasting benefits without the downsides, including cognitive benefits from deep ketosis, increased autophagy, weight-loss, and lower fasting glucose, while preserving your lean muscle mass.  

Will I try a sardine fast again?  Probably not, simply because I really don’t like sardines.  If you are also in that camp, don’t worry – there are other ways of getting many of the same benefits.  In fact, I also ran an experiment on myself using eggs instead of sardines, in which I got all the same benefits along with significantly more culinary enjoyment.  Stay tuned for an update on my egg fast!