By now you’ve probably heard of intermittent fasting; maybe one of your friends is doing it and swears by it, you’ve read an article touting the benefits, or you’ve seen it pop up on social media. When diet trends hit mass appeal, I get a lot of questions from clients about what the deal is and whether they should try it, so I thought we would dive in and unpack this popular diet method.
What exactly is intermittent fasting?
Very simply, it’s a system where you restrict the hours each day that you’re allowed to eat. One of the most common is the 
16:8 breakdown, which means you would only eat for eight hours during the day (i.e. from 1pm to 9pm), and you would fast for sixteen hours (i.e. from 9pm to 1pm the next day). Or you could shorten the fast to 14 hours and widen the eating window from 11am-9pm. You can start and end the fast at whatever time you choose. Some people will break up the week instead of breaking up the day; they might fast for 24 hours every other day, or maybe they choose to fast only 1-2 days/week. Another variation is to restrict calories to only 500 during the fasting days, instead of fasting completely. There are many ways to do intermittent fasting, but the bottom line is that you’re mainly restricting the hours of eating rather than the calories consumed. So now that you understand what it is, let’s look at the obvious question, why might someone do this?
Here are some claims about intermittent fasting: it will help you lose weight, boost metabolism, live longer, reduce inflammation, help blood sugar regulation for those with diabetes, and reduce risk for disease. But are any of these claims true?
Let me start by saying that I haven’t personally tried the more extreme versions of intermittent fasting as described above. Naturally I might fast for 12-14 hours based upon my schedule (i.e. I might stop eating at 8pm at night and then eat breakfast at 8am or 10am the next day). When you sleep, you fast, and breakfast is literally ‘breaking the fast.’ So to some degree, you’re probably already participating in intermittent fasting. But extending the fasting period is what people are talking about when they refer to intermittent fasting these days.
Here are some actual benefits that your body will receive from this practice:
- When you give your body a break from digesting, it allows time and energy for your body to be able to rest, heal, and repair cells. Some people even report a decreased recovery time for soreness after working out. Especially if you stop eating early enough at night so you go to sleep ‘empty,’ your sleep will be better and deeper healing and cell repair can occur while you sleep.
- Fasting also frees up energy in general since your body no longer has to work at digesting. People often experience a surge in energy during fasting.
- For those who do the variation of 500 calories/day on fasting days, they may experience a metabolism boost; shifting caloric intake can actually shake up your metabolism (which can get stuck in a rut) resulting in a boost. I sometimes recommend for a client to eat an all-vegetable meal (which naturally has fewer calories and is easy to digest) one or two nights a week to boost metabolism.
- It is possible that you might consume fewer calories during the day when intermittent fasting, since your eating time is shortened, which could result in weight loss.
- Fasting gives your pancreas a break from having to produce insulin in response to glucose in your blood, and might be good for diabetics because there are fewer hours with potential blood sugar spikes and crashes.
- Reduced inflammation can be a benefit, partly because there’s more recovery time for healing in between digesting, but partly because you’re not eating inflammatory foods for part of the day.
The Rebuttal:
- It’s not a realistic or sustainable way of eating for many people.
- When your body feels like it’s not getting the nutrients it needs, it can slow or shut down your metabolism and start storing fat… the opposite effect that you want.
- In my opinion the most important thing is WHAT you choose to eat, not WHEN. If you eat fewer hours per day but continue to eat sugar, refined flour, or other inflammatory foods, you’ll be counteracting any benefits you would otherwise receive from fasting.
- Simply eating a low glycemic, generally healthy diet, will require a much smaller amount of insulin than most people with Type II Diabetes are used to, and will give the benefit of stable blood sugar without needing to fast.
- Losing weight might not happen in reality, because even though it seems like calorie restriction should be naturally occurring when fasting, over-eating or making bad food choices during the other hours might happen in response. This will especially come into play if your body gets past the point of hunger in a survival sense and tries to compensate by eating a lot and storing it (we’re wired not to starve), and also if you’re naturally rebellious towards restriction, which I can tell you from my years of coaching experience is quite common (I’m guilty of this myself!).
- Your body needs nutrients, fat, protein, etc to function properly. If you’re busy, physically active, use your brain a lot, and are dealing with stress, intermittent fasting might not feel supportive. For instance, a light, low glycemic breakfast on a very active morning can do wonders for stabilizing blood sugar, boosting metabolism, and increasing productivity, whereas eating nothing might leave you feeling stressed and depleted.
Overall I personally don’t think it’s the way to go for weight loss. There have been so few studies done on intermittent fasting, but as of yet, it hasn’t been shown to result in more weight loss than good old-fashioned calorie restriction.
However, due to the natural healing abilities of our bodies, which increases when we’re not digesting food, I do believe that it can be beneficial when dealing with certain illnesses, or for those in need of healing for some aspect of their health. If you choose to use intermittent fasting for this reason however, you want to be careful to still get the nutrients your body needs. Remember that healing requires vitamins, minerals, nutrients, and also extra energy, so a balance of good nutrition and plenty of time to rest in between digesting, would be optimal.
Ultimately, I recommend that you do what feels good to you, so keeping in mind the above points, you can always give it a shot and see how you feel (you might want to give it a few days for your body to get used to it before making a judgement).
And if you do try intermittent fasting, let me know how it goes! While I probably won’t be joining you, I’ll be curious to hear all about it:)
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