NOTE: I've had many people tell me this article has motivated them to try fasting. Here's how to try it in the way that's most likely to ensure success.

It’s been 13 weeks since I wrote the in-depth post on my fasting experiment (read that first if you haven't already), which I originally only expected to try for 8 weeks. But the results have been so life changing that I’ve decided to continue doing it through at least the end of the year, and possibly indefinitely. Here’s what I’ve learned and experienced over the past couple of months, along with the pro-tips I recommend for others interested in trying it themselves, and answers to the questions I get most often.

The main thing I’ve learned in the past couple of months is that fasting is deeply misunderstood by people, including the reasons for doing it, the science and nutrition behind it, the actual experience of fasting, how it makes you feel, and how best to be supportive of someone in your life who’s giving it a try. Fasting just isn’t mainstream enough to make sense to people, and they often immediately respond with “I could never do that” (which is how I used to also feel before really diving into it).

From my fasting experience I’ve also become convinced that the obesity epidemic in America can be solved by integrating fasting elements into our culture. I don’t know if fasting will ever reach that level of cultural prominence, but I do now know with certainty that there’s a solution out there that works, and although fasting is a very individual thing, I’m convinced that it could be codified into an approach that could work for anyone. This also means that if you are unhappy with your current level of health, fasting is something you can do to fix it. It may not be the only thing you can do, but from experience I can tell you that it is absolutely an approach that will work. If you’re serious about trying to become healthy, fasting will work.

Pic at left is from earlier this year, before I started fasting. Pic at right is from a recent trip to Hawaii (thanks Amanda for the acrobatics, and Sarah for snapping the action shot!)

Here are my results from the past 3 months: The most obvious change is in my physique: I’ve gone from 245.8 lbs, which is a weight I’ve been at for the past 7 years, down to 209 lbs, a reduction of 15%. My body fat has decreased from 33.7% to 26.3%, a reduction of 7.4%, and my Body Mass Index has dropped below 30 for the first time in as long as I can remember. My muscle mass has improved from 32% to 36.1% (more on that later). I’ve dropped from XL to L shirts, and even put a medium sized shirt on at the beach the other day, which I never thought I’d do. My waist has dropped 4 belt buckle sizes, from a 38 to a 34, which has meant that I’ve had to donate most of my old clothes. But even more importantly, I feel great — sharper mentally and with more energy overall. I did a baseline series of blood tests when I started this fasting experiment, but I haven’t yet run the “after” set of metabolic panel blood tests, as I want to reach my goal first, which is to get my body fat below 20%. In July I dropped 2.8% body fat, then 2.3% in August, 1.2% in September and 1.1% so far in October. If I can keep a pace of about 1% body fat reduction monthly, I should be able to hit that goal by April 2016, and I’ll run the “after” blood tests then, along with an blog post update.

Although the changes to my physique are the most obvious ones, and the ones that everyone comments on (with people literally saying they don’t recognize me from older photos), those are the secondary benefits of fasting, and they pale in comparison to what I believe are its true benefits, which is that fasting promotes a healthier body that can repair its cells more efficiently, lower the risk of diabetes, lower the risk of coronary artery disease, better regulate blood glucose levels, fight off cancers more effectively, stay mentally sharp longer into old age, and possibly even extend lifespan. This is what makes fasting so misunderstood. People think it’s a diet, because that’s what they see. But I believe it goes much deeper than that. I believe fasting enables my body to perform better, for longer; maybe even decades longer. And few things are more meaningful than having an opportunity to craft a body that lasts longer and serves you better into old age, so you can do more of the things you want to do, with those you love, for longer.

A side note: If you don't know the important stats of your own body, like your BMI, body fat percentage, HDL, LDL, triglyceride levels, etc, then before you really consider whether or not you should fast, you'll have to decide if you want to get serious about your health overall. If you don't know your baseline, you won't know how much you need to improve to get to an overall level of health that's ideal for you.

The science around fasting is still in its infancy, so deciding to fast for reasons other than the immediate health benefits (which alone are tremendous) requires one to make some decisions today about what you want your life to be like several decades from now, and some of those decisions aren’t yet fully backed up by large-scale, randomized, controlled clinical trials, although the early science on smaller mammals and some human studies is promising and fascinating. Here are a few quotes to illustrate what I mean (with a bunch more in my original blog post, if you want to dig deeper):

  • "Together with our prior studies that showed decades of routine fasting was associated with a lower risk of diabetes and coronary artery disease, this led us to think that fasting is most impactful for reducing the risk of diabetes and related metabolic problems." - Medical News Today
  • “Prolonged fasting appears to shift stem cells of the immune system from a dormant state to an active state of self-renewal.” - Medical News Today
  • In mice, prolonged periods of fasting - repeated cycles of 2-4 days with no food - over the course of 6 months, killed older and damaged immune cells and generated new ones. - Medical News Today
  • "A study in the June 5 issue of the Cell Press journal Cell Stem Cell shows that cycles of prolonged fasting not only protect against immune system damage — a major side effect of chemotherapy — but also induce immune system regeneration, shifting stem cells from a dormant state to a state of self-renewal. In both mice and a Phase 1 human clinical trial, long periods of not eating significantly lowered white blood cell counts. In mice, fasting cycles then “flipped a regenerative switch”: changing the signaling pathways for hematopoietic stem cells, which are responsible for the generation of blood and immune systems, the research showed." - Michelson Medical Research Foundation
  • “Intermittent fasting probably lowers the risks of degenerative brain diseases in later life. Mattson and his colleagues have shown that periodic fasting protects neurons against various kinds of damaging stress, at least in rodents. One of his earliest studies revealed that alternate-day feeding made the rats' brains resistant to toxins that induce cellular damage akin to the kind cells endure as they age. In follow-up rodent studies, his group found that intermittent fasting protects against stroke damage, suppresses motor deficits in a mouse model of Parkinson's disease and slows cognitive decline in mice genetically engineered to mimic the symptoms of Alzheimer’s.” - Scientific American
  • “As the researchers report online today inCell Metabolism, the mice shed fat and were 45% less likely to fall victim to cancer. During their lean cuisine episodes, their level of blood sugar fell by 40% and the amount of insulin in the blood was 90% lower. And although brainpower usually declines with age, the mice retained more of their mental ability; they bested control animals in two kinds of memory tests, perhaps because they produced more new neurons in the hippocampus, a brain area crucial for memory. - Science Magazine
  • "Although the clinical results will require confirmation by a larger randomized trial," they add, "the effects of FMD cycles on biomarkers/risk factors for aging, cancer, diabetes, and CVD, coupled with the very high compliance to the diet and its safety, indicate that this periodic dietary strategy has high potential to be effective in promoting human healthspan." - Medical News Today
  • “People on the diet had improvements in blood glucose and decreased body weight compared to the control group. Those with initially elevated C-reactive protein levels (a marker of heart disease risk) had lower levels, while those with normal levels had no change.” - NIH Research
  • “By the end of three months, the participants in the FMD group had reduced markers of aging, diabetes, inflammation, heart disease, and cancer. Importantly, the FMD was linked to lower levels of the hormone insulin-like growth factor 1 (IGF-I), which previous work has found is connected to cancer risk and aging” - Forbes
  • “We do know for certain that fasting can have beneficial effects for the heart— significantly changing blood cholesterol levels and reducing the risks of heart disease. There is also evidence that it can combat obesity, lower blood pressure, lessen the symptoms of rheumatoid arthritis and reduce the risk of Type 2 diabetes. Anecdotally, some patients find fasting before chemotherapy lessens the negative effects of the powerful cancer drugs.” - FOX news

As I read articles like those, coupled with my experience over the past three months, I quickly went from “I could never do that” to “how could I not do it?” The data is strong enough for me to be willing to make a long-term bet on the health benefits of fasting, and even if they don’t pan out, it’ll still have very much been worth it for the immediate benefits in my physique and energy levels. Here are some of the common questions I’ve gotten from people who are curious about what it’s like to fast:

“How hard is it?” This is probably the one I get the most often, and the answer is a bit nuanced. Fasting the way I choose to do it isn’t easy, and I’ve watched some people around me not be able to stick to it. They just get too hungry. But I’ve also built up to a pretty intense version of fasting over the past three months, which I describe below. There are milder forms of fasting that one can start with, and I highly recommend starting with something sustainable for you as you learn the limits of your mind and body. Here are various options, from what I consider easier to harder:

  • Overnight fasting for 8ish hours: The good news is that unless you get up in the middle of the night to eat, you’re already doing this one. Congratulations! They don’t call it ‘break-fast” for nothing; you’re literally breaking your fast from the night before when you eat breakfast. If you want to slowly build from this base you’ve already established, try eating your last meal earlier. Maybe you don’t let yourself eat after 8pm, for example, and then don’t eat again until 8am the next morning. You’ve just extended your 8 hour fast by 50%, to 12 hours this way.
  • 8/16 fasting: This is a more extreme version of the overnight fasting above: You only eat in an 8 hour window each day; say from 10am-6pm, and then you fast for 16 hours. Most people who utilize this approach maintain that eating vs. fasting window for 5 to 7 days of the week. I skipped over this level so I can’t speak to it, but I’d love to hear from people in the comments who do it.
  • 6:1, 5:2 or 4:3 fasting: This is my preferred fasting approach. I fast for two (5:2) or three (4:3) days per week. Fasting for 3 out of every 4 days of the week means fasting every other day, which is why a 4:3 fast is also often called Alternate Day Fasting, or ADF. NOTE: There’s also a modified, easier version of these fasts which is called a “Fasting Mimicking Diet” or FMD. There’s some science that shows that one can consume up to 25% of your normal caloric intake and still achieve the scientific benefits of fasting described above. This would mean, for example, that a male could consume about 600 calories on fast days. When I started fasting, I would do FMD by having dinner on fast days, but I pretty quickly dropped that because by dinner time I wasn’t hungry. More on that, plus how I choose between fasting for 2 or 3 days per week, below.
  • Multi-day fasting: This is what most people think about when they first hear about fasting; going without food for days at a time. I’ve never tried this; while I might at some point I don’t feel the need to now. The science to date is pretty solid that you don’t need to fast for consecutive days in order to reap the benefits of fasting, so my current attitude is “why put myself through it if it’s not necessary?” Dr. Michael Mosley did a four day fast in the BBC documentary on fasting I embedded in my first post; it’s a good watch to understand what the experience was like (spoiler alert: not great).

“What kind of fasting do you do?” I’ll fast for two or three non-consecutive days per week, with each fast day comprising a 30 to 36 hour period without food. An example would be that I eat dinner on Sunday night, then have nothing except water, coffee or tea on Monday, and I don’t eat again until breakfast on Tuesday. Depending on the week, I’ll either do that one more time (say, on Thursday or Friday) or I'll do it two more times (say, on Wednesday and Friday) later in the week. I try to plan my fast days based on how much I know I’ll be eating on other days. For example, I was just on vacation in Hawaii for the week and knew I’d be eating well there, so for the two weeks leading up to Hawaii, I fasted three days each week instead of my usual two. Then, I fasted on the day I traveled to Hawaii, as well as the day I traveled back from Hawaii, which meant that I was able to fast just one day while actually in Hawaii. I found this to be a good balance between indulgence and fasting.

“Do you eat more on your non-fasting days?” For me, fasting has been an incredibly liberating experience, as I wrote in my initial post, because it’s the very first time I’ve ever felt like I’m in control of my body. I’ve always had a really hard time not eating when food is in front of me, even joking that food ‘talks’ to me — or at least, that’s how it feels. Fasting removes all of that difficulty: There are days when I eat, and days when I don’t. On the days I eat, I don’t try to control myself like I used to, which means that I definitely eat more than when I was constantly battling myself. But over the course of the week, my overall calorie count is still greatly reduced. For example, I used to eat 2,500 calories per day, seven days per week, for a total of 17,500 calories in a week. There’s science showing that people who fast eat about 115% of their normal intake on non-fasting days, which feels about right to me. That means that in 5:2 fast weeks, I’m ingesting 2,875 calories per day, five days per week, which still creates an overall deficit of 3,125 calories in a week (and in weeks when I fast 3 days, a deficit of 6,000 calories each week). So fasting gives me the ability to not need to battle my food consumption desires on my eating days, which is incredibly liberating.

“How does nutrition play into fasting?” Our family prioritizes fresh, organic, and less processed foods (i.e., the foods you’ll find around the edges of the grocery store, not in the middle aisles). I limit all types of sugars(fructose, table sugar, honey, agave, etc) by not adding them to anything I eat (i.e., I don’t add sugar to coffee) and I also treat carbs (bread, pasta, beer, etc)as indulgence vs. everyday items. You can think about fasting and nutrition as separate but related: You don’t have to change your nutritional habits in order to begin fasting, although by fasting you’ll likely become more aware of nutrition generally. The more hardcore you are with nutrition, the more effective fasting will be.

“Aren’t you starving all day?” Surprisingly, no. On fasting days I’m hungriest between lunchtime and late afternoon for about five hours. By dinnertime, I’m not very hungry and by the next morning, I’m not at all hungry. If you can get through the part of the day when you are hungry, it’ll go away. Not being hungry in the evenings is what allowed me to drop the evening meal on my fast days.

“Do you exercise when you fast?” Yes! Exercise has played a key part in my fasting. As I wrote in my original post, fasting is a part of a larger goal I have to get back into the kind of shape I was in when I was younger. I primarily do two things: CrossFit 3x per week for strength, and indoor rowing 4x to 6x per week for endurance and general fitness. Interestingly, I’ve found that if I do CrossFit the day after a fast day (say I fast on a Tuesday, and then have CrossFit on a Wednesday morning) I’m noticeably weaker. Fasting keeps me from hitting personal records around max weight movements as quickly as I was before I started fasting. However, I’m also getting leaner, which helps me improve in other CrossFit workouts that aren’t just about lifting max weight, and as a percentage of my weight, my muscle mass has increased, so not hitting PRs as regularly is a trade-off I’m happy to make. In contrast, I find that my rowing often improves on fast days, which was completely unexpected. If I fast on a Tuesday and row that night after fasting all day, I find that I can often hit a rowing PR. There’s something about having already exhausted the glucose in my body earlier in the day, and rowing with energy my body is getting from fat stores that makes for a longer, more even power output. It was really a surprise. So I’ve found fasting to be bad for pure strength output but great for endurance output.

“Will you fast forever?” Possibly. All I know right now is that I’ve found something that gives me control over my body in a way I’ve never otherwise had. I expect that once I hit my goal of getting my body fat below 20%, I’ll likely switch between 6:1 and 5:2 fasts, meaning on some weeks I might only fast one day per week, and on other weeks (say when I know I’m going out to a big dinner that week) I’ll fast two days. What I do know for sure is that I’m happily extending my eight week test through at least the end of the year, and likely through mid next year so I can reach my goal.

“What’s the best day of week to fast?” I’ve found weekdays, when my mind is on work, are much better than weekends. I’ll only fast weekdays with one exception: When I’m traveling, I’ll fast on a travel day, which is often a weekend day, because eating while traveling is usually a pain anyway since it’s hard to find healthy airport food. I’ve found that traveling West, while generally easier, is harder from a fasting perspective since the day is longer than when traveling East.

If you'd like to give fasting a shot, I highly recommend starting with the hour-long BBC documentary embedded in my original post. I've also been reading a free PDF e-book written by Dr. John Berardi, a nutrition expert, who tried various types of fasting and wrote a detailed review. But most of all, I encourage you to post your questions and comments below. I'd love to know what kind of impact fasting has in your life!