Intermittent Fasting – Healthy or Harmful?

My Unhealthy Experiences with Intermittent Fasting

For the past few years, I had been a huge devotee to the “paleo” or “primal” lifestyle. Although I can’t quite call myself paleo anymore, I still find quite a bit of common ground with their community.

In this time period, I’ve spent hours upon hours scouring through the blogs of famous paleo authors, such as Mark Sisson or Robb Wolf. One topic that I had seen brought up frequently was “intermittent fasting” – the process of not eating for generally short amounts of time. At first I was disinterested as I was always told that skipping meals is bad for you. Eventually, I was intrigued.

One claim that really caught my eye was that intermittent fasting causes a huge spike in serum human-growth-hormone levels. I believe this is the study that everyone cites to back-up the “hGH” claim. By now, I was ready to hope on the fasting-bandwagon, because hGH increases collagen synthesis. For all of you who’ve read my previous posts, you know that my joints have been banged up. Increased collagen synthesis means your cartilage, tendons, and ligaments will repair more quickly. This is EXACTLY what I needed.

In the end, things weren’t what they thought to be and I discontinued fasting. I actually found intermittent fasting BAD for my health, but I’ll explain why in a minute. Here are the rest of the benefits of intermittent fasting:

So, who wouldn’t be tantalized by all of these potential benefits? It really does appear that intermittent fasting is healthy. So, I began to fast intermittently using various methods, starting out with daily 8-hour eating windows and progressed to fasting twice/three times per week for 24 hours at a time. Basically, I’d eat dinner the night before, and not eat the next day until dinner time, making it 24 hours without food. I’d always try to eat my day’s worth of calories for dinner, but always came up slightly short.

IF Wasn’t the Holy Grail It Seemed To Be.

At first, it was great, and I became a huge fan of intermittent fasting. I definitely experienced the touted cognitive improvements. My mind felt so clear and sharp. I loved not having to worry about cooking so frequently, too. I could wake up, and go about my day without being forced to go to the kitchen. Also, my weight went down by a few pounds and my body composition improved. No complaints there.

After a while, things got a little messy. Although I was never physically hungry, my mind craved food. I began to think about food THE ENTIRE DAY of the fast. I’d get antsy and not be able to focus on my work. I was definitely stressing out too much over my intermittent fasting protocol.

Is intermittent fasting harmful or healthy?

I miss food.

What sent me over the edge, however, was when I learned about the effect of collagen synthesis during fasting. In acutely-fasted guinea pigs, collagen synthesis significantly dropped at the 24-hour mark. What I originally thought was going to help strengthen my joints, was potentially weakening my joints. Screw that, I’m not risking weak joints. I haven’t fasted since.

After having the chance to think about it over the last few months, I’ve come a conclusion. Unless you are a completely healthy, stress-free, sedentary person, or are experimenting on your own body, you should probably not intermittent fast.

Why Intermittent Fasting Can Be Bad For You

The way I see it, our bodies are fighting to maintain equilibrium between catabolism and anabolism. Catabolism is the break-down of tissues and the release of energy. Anabolism is the build-up of tissues and the taking-in of energy. Catabolism allows us to use and abuse our bodies, and anabolism allows us to recover.

With lack of perfect sleep, regular exercise, and constant mental stress, most people in the modern world are too catabolic. Our bodies undergo too much stress and break-down, and don’t experience enough recovery. We do certain catabolic activities, such as exercise, that make us feel good for a short time, then we break down and get injured or sick. The same situation applies to intermittent fasting. I felt great, but fell apart pretty badly soon after.

For the common person, intermittent fasting my cause be too much catabolic stress and quickly lead to diminishing returns. This is similar to training too much and not recovering afterwards. If you break yourself down too much where your body can’t keep up, you won’t grow. Progress comes to a screeching halt, and even turns into a loss.

Anyway, enough hypothetical discussion. Let’s examine the studies and see how fasting affects anabolic processes.

Intermittent Fasting Reduces Collagen Synthesis

I previously just mentioned how collagen synthesis is negatively effected by intermittent fasting. Here’s the original study I found on decreased rates of collagen synthesis due to fasting in guinea pigs. After 24 hours of fasting, the rate of collagen synthesis of the fasted group was 50% of the rate of the control group. By 96 hours, the fasted group’s rate was at 13% of the control group’s. This drop in collagen synthesis is HUGE, whether it be 24 hours or longer.

After 72 hours of refeeding, the fasted group was back to normal.

Intermittent Fasting Reduces Protein Synthesis

In the same study linked above, the rates non-collagen protein synthesis was also observed. After 24 hours of fasting, the rate of protein synthesis of the fasted group was 75% of the control group’s rate. After 96 hours, it drops down to 54% . Protein synthesis bounces back to normal rates after 72 hours of refeeding.

Intermittent fasting healthy or harmful?

Dat der protein molecule, next to its RNA buddy.

Interestingly enough, collagen synthesis reduces much more quickly than regular protein synthesis does during intermittent fasting.

Intermittent Fasting Reduces Bone Mineralization

Now for bones, I found a website that had a page full of abstracts to different studies regarding caloric restriction and bone density.

Upon a quick review of the bunch of studies they’ve listed for us, I found another strike against fasting. There is a noticeable negative impact on the skeletal structures of monkeys with months-long caloric restriction. The website I found seems to be supportive of caloric restriction, so they can be cherry-picking here. However, I haven’t been able to find many other studies on the internet.

Conclusion: Intermittent Fasting May Negatively Impact Anabolism

Whatever you do, listen to your body and be careful!

Evidence links long-term fasting and caloric restriction to reduced anabolic capacity. However, this information doesn’t allow us to make bold accusations against intermittent fasting. Each study is in the scope of days or months, not hours which is what intermittent-fasting entails.

It could be that refeeds within 16-24 hours of intermittent fasting have a “rebound effect” for the body’s anabolic processes, bringing them back to baseline or higher. However, conventional wisdom states that if you want to be big and strong, you should eat like a horse.

With that said, I do think the benefits exist for intermittent fasting. That’s if you are getting enough sleep, not experiencing too much mental stress, eating enough calories when not fasting, and so on.
That really sums up my opinion of whether intermittent fasting is healthy or harmful.

It may not even be worth trying out intermittent fasting, given that most folks today live such stressful lives. That’s just my two cents, though.

Hell, I might give intermittent fasting another try in the future, but until then, I’m fine with regular eating.

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  1. Photo Credits
    Empty plate. Author: Carly Sheil.

  2. I’m curious: what are the “diminishing returns” from “too much catabolic stress?”

    • At the risk of sounding “bro-science-y”… Basically, fasting is a catabolic stressor, just as exercise is.

      Here’s my logic: with the introduction of a new stimulus, our bodies seem to adapt readily. However, pile on more and more catabolic “stimulus”, such as fasting and exercise, without enough time to recover, you break down.

      So basically, I found fasting to be nice at first, but with a lot of other catabolic stressors, the positive results dwindled and soon became negative.

  3. I’m glad you’ve outlined how IF can be detrimental at >24 hours – <96 hours.

    But who would want to fast that long? I like to fast from 16-18 hours and work out high volume high intensity on the 15th-16th hour. I feel great and pig out for 6-8 hours with healthy food (fat, protein, carbohydrates).

    The only time IF is bad for you is if you do it wrong or don't have the right information, such as the information listed in this article.

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