If you’re reading this, you have probably also been perusing other blogs that make fantastical claims about the benefits of the ketogenic diet and intermittent fasting. Like anything else in the United States, the more extreme the better, so now we have people pushing 100% carnivorous diets – not even veggies or fruit – making the hardcore keto community look like a bunch of granola-crunching, bleeding-heart vegans. Gotta love America!
The problem with zealotry of any stripe is that, when extremists appropriate a reasonable idea, the moderates of the world become less receptive to the merits of that idea. Let’s use politics as an illustration: for decades, US policy on North Korea has not moved the needle in a positive direction. President Trump recently decided to take a completely different approach to the situation, engaging Kim Jong Un in one-on-one talks. Trump thinks that he can persuade North Korea’s leader to denuclearize by assuring Kim Jong Un we have no interest in nuking his country and enticing him with integration into the world economy, lifting his entire country out of poverty.
Is this gambit going to work? It’s like predicting movement in the stock market – nobody knows. I’m not interested in debating the merits of Trump’s plan. I’m merely pointing out that, when Trump indicated his intention to hold a summit, moderate voices were highly critical. “That’s not the way we do things,” was the primary message I heard. To me, it felt like a knee-jerk rejection of Trump’s plan because it was Trump’s plan. Listen, decades of insisting on concessions from North Korea before sitting down to the negotiating table in a meaningful way has produced bupkis. So why not try a different approach that employs the not-so-radical strategy of…talking?
Bringing the conversation back to a realm in which I actually have some expertise and not just barely informed opinions, I want to talk about intermittent fasting (IF). This practice has gained popularity, especially among low-carb, high-fat (LCHF) enthusiasts. This makes perfect sense, as fasting is another way to encourage the body to enter ketosis, and we know that ketosis has the potential to do some great stuff. However, because the ketogenic diet (KD) is rather extreme, IF gets tarnished by association. [HD: As a quick aside, KD enthusiasts, please don’t leave long comments about how the KD is easy to follow. Maybe it is for you, but the majority of people out there will try it and fail.]
As I discussed with Dr. Bret Scher on The Low Carb Cardiologist Podcast, I first approached the concept of IF with my usual degree of skepticism, asking “Why is this a stupid thing to do?” I then dug into the research, which means I read numerous scientific papers – not blogs – from (mostly) peer-reviewed medical journals. Although human data is not exactly robust at this point, there is enough total data to suggest that IF is not stupid. In fact, it may have some important health benefits. This is not a medical-o-pedia site, so I will not recreate all the physiology in this post. If you’d like more detail, I highly recommend this review article from the journal Obesity: Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting.
When it comes to IF, on one end of the spectrum, the potential benefits by which many people seem to be intrigued are weight loss and improved insulin resistance/diabetes control. On the other end of the IF fascination-spectrum, there are hardcore bodybuilders who strategically plan their meal timing and composition in the quest to gain ever-increasing amounts of muscle without a concomitant gain of fat*. The question I have is: can IF benefit the large group of people in between the ends of the spectrum? In other words, if you’re not overweight, in fairly decent shape, and not interested in lifting very heavy things, what can IF do for you?
Unfortunately, it’s difficult to answer this question in a data-free zone. All we have are anecdotes from the blogosphere. Although it burns my muffin when people cite anecdotes as if they’re data handed down on stone tablets, I think it can be interesting to read about the experiences of someone like us – particularly if we trust that person to give a balanced assessment. In that spirit, I’d like to share my experience with IF, specifically Time Restricted Feeding (TRF).
HD, the Pseudo-Athlete
Regular readers know me as an Endocrinologist who hates diabetes, loves transgender care, and rails against a medical system that is burning doctors out at an alarming rate. Along the way, you’ve probably picked up a few personal tidbits about me, but I haven’t discussed my own diet and exercise regimen much. Frankly, telling people “the way I do it” seems self-indulgent and has the potential to come off as pedantic. But, in order to know if my experience with TRF is at all extrapolatable to you, I think it’s important you know some basics about me and what I hoped to gain from TRF. If you don’t like it, let me know in the Comments!
In my younger years, I played competitive sports in some fashion right up until my early 20’s, and then it all went downhill from there. What happened? Life happened, like it does to pretty much everybody else who gradually slides from fitness into a less desirable state of being. Medical school, residency, fellowship, and then my real doctor job occupied most of my waking moments, so I learned to cram my workouts in when time permitted. Being relatively vain, I focused on strength training, to the exclusion of cardio, flexibility, and mobility training. I dutifully lifted weights on a consistent basis, punctuated by hikes, bike rides, and other more cardiovascular activities. But my gym lifting routines were stale, the outdoor activities weren’t occurring as frequently as they should, and I wasn’t thinking much about my diet. I had some decent muscle definition, but I also had some subtle love handles forming. Peddling my bike up a steep hill, with my toddler on the back, caused my heart to nearly explode out of my chest – I was clearly not the same man as I was a couple decades ago!
It took a health scare to jolt me awake, lighting a blazing inferno under my butt to make some changes. I began focusing more on my diet, reducing starchy carbohydrates and simply making better choices. I started learning more about exercise, experimenting with a few personal training sessions, videos and numerous workout styles. A close friend who had already ridden in this rodeo introduced me to P90X, Insanity, and other high-intensity, interval-training (HIIT) workouts. I became addicted to the adrenaline rush provided by these workouts, to the point where my mood would deflate if I went too many days between sessions.
I continue to take two steps forward, one step back, as I am slowly learning how to listen to my middle-aged body. Apparently, it is very easy for me to overtrain, so I have to be judicious in my workout selection. I now exercise 4-7 days per week, though not every workout involves massive calorie burn or high-repetition strength training. I try to alternate HIIT workouts with more moderate running, hiking, and biking. I must do a dedicated yoga or flexibility/mobility routine once weekly or every other week; if I don’t, I tend to have more aches and pains.
At this point, I would consider myself a pseudo-athlete. I think I’m fitter than the average weekend warrior who bikes 50 miles and then hobbles around in pain until the following Friday. But I am not going to win any CrossFit competitions. And I’m definitely not breaking records of any kind. Although I have a respectable six-pack, I don’t quite meet strength coach-extraordinaire Charles Poliquin‘s credo, “You need to have penis skin over your abs.” [HD: I’m paraphrasing this from an interview Charles did on Tim Ferriss’ podcast, in which Charles stated that one should have “penis skin” over one’s abs in order to “deserve” to eat any carbs.]
At this stage of my life, my primary fitness goal is to not get hurt. I am often nursing some tendinitis here and some knee/shoulder pain there, but I am typically able to work around my IOD (Injury Of the Day). I can keep up with my kid and enjoy the great outdoors, so I’m just trying to do my best to maintain the status quo, as the status quo is pretty darn good [HD: Just because I’m happy with my current level of fitness doesn’t mean that I’m not on a quest to become stronger, faster, and more durable. I’m just not willing to risk injury in the pursuit of it all.] With that in mind, on to my experience with TRF.
What did I want from TRF?
Given that we’ve established I’m already in decent shape and simply trying to maintain it, what did I hope to gain from TRF? Well, I’ve mentioned on Dr. Scher’s podcast that my fasting blood sugar tends to run in the 100-110s with a Hemoglobin A1c around 5.6. I’ve been laboring under the assumption that I have prediabetes (more about this later), so I was very interested to see if my blood sugar and A1c would improve with TRF. However, because I am already lean, I planned to eat enough calories to keep my weight constant, thereby isolating the effect of time restriction from the effect of weight loss. As you all know, weight loss tends to improve blood sugar and A1c levels, so I did not want that confounder.
As for other effects of TRF, I wanted to see if my body composition would noticeably change. Additionally, I became fascinated by the concept of fasting having anti-cancer and anti-dementia potential, but obviously there is no way to assess that during a 6-month trial. Nonetheless, I figured that if I liked TRF for tangible reasons, I might continue it for the vague promise of eventually not getting cancer or Alzhemier’s disease. For the record, I am fully aware if I never get cancer or Alzheimer’s, it might simply be good luck and good genetics, having nothing to do with TRF.
So, before starting TRF, I asked my poor primary care doctor to order a battery of fasting labs for me. Hey, at least I didn’t ask for a reverse T3. Here are the highlights:
As you can see, my fasting blood sugar puts me into the prediabetic category, with an A1c that is pushing the limits of what is considered totally normal. But my insulin level is at the lower limit of detection of the assay (2.0 uIU/mL), and my triglycerides and HDL look like those of a lean, insulin-sensitive individual.
I did not make this overly complicated. I simply picked four days out of the week when it’s convenient for me to skip breakfast. Why only four days? Number one: I enjoy the ritual of breakfast and didn’t want to completely give it up. Number two: I am often the house chef for family breakfasts, and it’s hard to smell delicious food and not actually put it in my mouth. Given that I was interested in finding the MED (minimum effective dose) for TRF, I figured I could start with 4/7 and titrate up from there if desired. I’ve been consistent with this schedule since January 2018, with the exception of when I’m on vacation, so it’s been about five months. My fast lasts from post-dinner one day to lunch the next, about 16 hours. I still drink one cup of black coffee in the morning in order to feel like a functional human being [HD: I used to put only a splash of cream into my coffee, so eliminating that was easy].
My Experience with TRF
The first four mornings of fasting, I had quite the gnawing sensation in my stomach. It mostly resolved with breaking the fast, though it was tough to figure out how much food to eat. My brain seemed confused by the schedule, and I didn’t feel like I could trust my appetite regulation center. A few times early on, I felt satisfied by a reasonable amount of food, but the gnawing didn’t resolve until I ate more. As of day five, though, the gnawing disappeared and fasting has mostly been easy. Occasionally, I feel intense hunger before the 16-hour mark, so I have broken the fast an hour early a few times.
One benefit of TRF that surprised me is the absence of a drive to eat around 9:30-10am. On days when I eat breakfast, I am always hungry by mid-morning, so I tend to snack on nuts, veggies/hummus, or fruit/almond butter. On TRF days, I typically do not have intense hunger. Of note, my breakfasts are usually fairly high in protein, but they do contain some carbs, so I wonder if I could achieve the same effect by completely eliminating carbs from breakfast [HD: LCHF enthusiasts swear that carb ingestion begets carb cravings, and I think they may be right].
Anyway, it took me several weeks to figure out how to eat enough during the day to maintain my weight. I tried breaking the fast with a typical breakfast, followed 2 hours later by a typical lunch, but that just felt like one meal running into another. Then I tried eating a small snack, followed by lunch a little later, but I found I wasn’t hungry enough to eat a proper lunch. Ultimately, I settled on breaking the fast with a slightly larger lunch than usual. I also got more religious about drinking a post-exercise protein shake after every workout. After losing a few pounds early on, I quickly regained them and have maintained my weight exactly at baseline. I will admit it’s possible that my body is smarter than I, meaning it may have lowered my resting metabolic rate to account for a mild caloric deficit. Since I’m not tracking calories, I just don’t know.
Remember earlier when I mentioned I’m vain? Well, one thing I’ve noticed with TRF is that I seem to have better muscle preservation/more definition, even weeks when I find myself doing more cardio and less resistance training. There are some interesting potential mechanisms involving growth hormone and other factors which I may dig into further in a future post. As for the timing of exercise, I typically work out in the afternoons on work days, and in the mornings on non-work days. I tried doing a couple of workouts in the fasted state; let’s just say they didn’t go well. One was HIIT (I totally bonked), while the other was lifting (didn’t feel as strong as usual). I have not yet tried a moderate-intensity run in the fasted state; perhaps that will work out better.
Overall, I’d say my subjective experience with TRF has been neutral to slightly positive. I have the same amount of energy, and I have the same problems with sleep (sometimes good, sometimes not, still haven’t figured it out). I like not feeling hungry mid-morning on fasting days, as it frees me up to focus on other things. So far, I haven’t found a workout I can do in a fasted state, but I also haven’t tried very hard. I like the aesthetic benefits with respect to muscle preservation, though I’m still not sure I haven’t imagined the whole thing in an elaborate placebo-hallucination. The question is, have there been any objective benefits?
|January 2018||May 2018|
|Glucose||109 mg/dL||112 mg/dL|
|Insulin||2.2 uIU/mL||2.1 uIU/mL|
|hsCRP||<0.20 mg/L||not performed|
Objectively, I’m going to say there has been no statistically significant difference in my metabolic parameters. Is it because I’m already as good as I can get? Is it because I need to up-titrate the dose of TRF to 7/7? Should I start fasting during vacations? Of course not – that’s just crazy talk.
For now, I will likely continue to experiment with TRF, as I think there may be some long-term, less tangible benefits to be had. As for the hyperglycemia issue, don’t think I’ve forgotten about that. I hope to have some exciting stuff to share with you about that in the future, as I have been reaching out to some pretty smart researchers in the diabetes world about the increasingly appreciated phenomenon of hyperglycemia in insulin-sensitive (pseudo-)athletes. Until then, I should probably rein in the chocolate-chip cookie eating.
*If you want to dive deep down the rabbit hole of intermittent fasting for bodybuilders, read everything on Martin Berkhan’s site Lean Gains. I am a huge fan of his no-nonsense writing style. If you think I’m blunt, Martin is me on steroids (figurative steroids, not literal steroids). And, as they say in Boston, he’s “wicked smahhht.”
It’s your turn now. Have you experimented with Intermittent Fasting in any form? What positives/negatives have you noticed? Did you get pre- and post-experiment blood work? What were your results? Have you figured out how to exercise in a fasted state? What works for you? Comment below!
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