<-- Map of summer 2018
     climbing roadtrip 
     (click to enlarge)

7-Day Fast
(& my experiences so far with the ketogenic diet)

TR #: 315

Training for alpinism.


This "trip report" is not about a climb. However, it is about a topic that several climbers I know are interested in: fasting and ketogenic diet. I don't go into too much background detail about either of these topics (Google can help you with that), but just outline my experiences with them and provide a day-to-day account of my experiences on a 7-day fast, where I consumed nothing but calorie-free liquids. Fasting and the ketogenic lifestyle are not for everyone: they are a real challenge physically, mentally, and socially. In fact, I would probably not recommend either to most people I know. But in my experience fasting and keto do have performance-enhancing results that are particularly helpful to endurance pursuits such as climbing. There are several high-performance athletes who swear by fasting and/or the ketogenic lifestyle, and I'm guessing there will be an increasing number of such accounts as these ideas become less crazy and more mainstream. See the end of this trip report for a discussion on my experience with the performance-enhancing effects of both fasting and keto.


I've dealt with various gut issues for as long as I can remember. In 2011, I had a MRSA infection in my leg and had to take a 6-week course of IV Vancomycin, which pretty much killed off all bacteria (bad and good) in my body. I don't think my gut ever quite regained a healthy bacterial balance, and by January 2017, following a bout with the flu, I was experiencing a raging bacterial overgrowth (SIBO) in my small intestine. Furthermore, blood tests revealed a good deal of non-specific autoimmune antibodies in my body, indicating my body was fighting itself in some way (more on this later in the June 2019 update). It took an entire year and over $10,000-worth of frustrating doctors appointments, pointless expensive procedures, and bandaid treatments before I diagnosed the SIBO via a self-ordered $150 breath test and an appointment with a naturopath. A round of antibiotics—Rifaximin (ordered from India because my insurance wouldn't cover it)—in December 2017 tamed down the bacterial overgrowth in my small intestine. 

At some point during this process of problem-solving my health issues, I began to read stuff about the ketogenic diet, and became intrigued. The ketogenic diet is a very low-carb, moderate-protein, high-fat diet; essentially, this the body begins to run off of fat. I figured depriving my gut of carbohydrates was a good a way as any to discourage the bacterial overgrowth from returning.

I maintained a strict ketogenic diet for about four months (Jan-April 2018). My ate mainly aged cheese, eggs, meat, nuts, and salad. I aimed for 20-30g of net carbs each day; almost all of these carbs came from leafy greens. On the ketogenic diet, I felt amazing—I had such constant energy and mental clarity, almost like a machine that could run forever, even after several hours without food. Plus, my digestive issues disappeared completely. And I lost 10 lbs without trying.

So why did I stop the ketogenic diet after four months, if I was feeling so good? I suppose it was a combination of reasons. For one, the ketogenic diet is pretty limiting, and I began to miss some of my favorite foods. Secondly, the bacterial balance of my gut (the main reason I had started the diet) seemed back to normal. And third, I was getting a bit weary of feeling like I had to justify myself all of the time about my unusual diet. By the time May 2018 rolled around, I had slipped back into just a "low carb" (100-150g net carbs) diet.

As Summer 2018 progressed, my digestive issues and the SIBO began to return. My body was still feeling fit and healthy, but not to the degree it was on the ketogenic diet. I yearned to feel awesome again. But I was finding it difficult to get the ketogenic diet started this time around. In mid-August, while climbing a burly V-slot on a climb, I strained a rib muscle and had to clear my schedule of physical activity for a couple of weeks. I was risking going crazy if I didn't make a plan for this time. I decided this was an opportunity to try a 7-day fast, something I'd been wanting to do at some point anyway as a personal challenge and life experience. The plan was that this would kickstart re-entering my ketogenic lifestyle. 

(June 2019 update: Apart from an occasional week or two where my ketogenic diet just meant low carb (~100-150g net carbs), I have maintained a ketogenic diet (~30g net carbs) since I wrote the report on this page in September 2018. I am still surprised at times by how much keto makes me feel like a machine—constant energy even after not eating for several hours, no afternoon slumps or need for caffeine, no hunger during the day or cravings for carbs, and the added benefit of greatly reduced indigestion and bloating. In April 2019, I started taking an immune-suppressant drug (Plaquenil) to deal with my autoimmune issues (which continued even after the SIBO was gone), and it seems to be helping. Interestingly, there is a lot of anecdotal evidence out there that a low-carb diet can help with autoimmune issues, so it is possible my autoimmune issues are not as bad as they could be if I were not keto.)

(Dec 2019 update: I moved to Colorado, quit the Plaquenil, and have continued bouncing back and forth between a keto and low carb lifestyle. Feeling better than I've felt since I was in my early 20's.)


"You're not going to eat anything for a week!?" (Yep.) "So you are just going to drink your calories, right?" (Nope. No calories.) "That's impossible. Only people in the Bible did that." (No, it's not. People do it all the time. Some people fast for a few weeks or longer.) "That's unhealthy." (Fasting is not to be equated with starvation or nutrient deprivation. Personally, I believe there are some incredible healing benefits to fasting, both for short-term and long-term fasts.) "You're kind of extreme, aren't you?" (Yeah, maybe I'll agree with that.)

Fasting is not a new thing for me. For years now, my normal daily routine involves intermittent fasting. This means that most days I do not eat anything until mid-afternoon, essentially fasting for somewhere between 16-20 hours every day and eating within a 4-8 hour window. My main reasons are convenience, productivity, avoiding digestive issues during the day, and controlling appetite, and by this point it has become such a part of my daily routine that I don't consciously think about it. I find I am most productive and efficient with my time during the 16-20 hour fasted window, so its been a great way to make the most of my time. I've also experimented with a few 1-3 day fasts over the last few years. But I've always struggled with the second and third days of a fast, often feeling a bit low on energy and giving in to the cravings and hunger. I've read numerous accounts that suggest that once past the second or third day, a fast becomes much easier, and that the lack of energy is from a drop in electrolyte levels rather than a lack of calories (insulin helps the body retain sodium, and without insulin being produced from eating food, salts pass much more quickly out of the body through the urine). For awhile now, I've had this growing (and perhaps a tad masochistic) desire to try a 7-day fast, out of curiosity of how my body will feel during that time, and also as a personal challenge. Shedding a few pounds is a nice benefit as well.

Bellow is a day-to-day account of my experiences during the 7-day fast. During the fast, I drank only zero calorie drinks (water, coffee, and flavored drinks). Since I had read that the key to keeping energy up during a fast is maintaining a good electrolyte balance, so I also ingested some salts every day (following the Snake Juice recipe of 1 tsp potassium chloride (No Salt), 1/2 tsp sea salt, and 1 tsp baking soda). 


Day 1 - Aug 22
- 3:20 pm: Due to my routine of intermittent fasting, Day 1 so far has been no different than normal. I am beginning to feel a tad hungry, but that might just be out of routine of normally eating my first meal around this time of day. Nothing I cannot ward off by drinking a bit of water.
- 9:00 pm: I felt a few stomach growls around dinnertime, but I was pretty involved in a practice GRE exam at the time (I'm applying for a PhD in Applied Mathematics for Fall 2019), and by the time I finished the GRE, the hunger had passed. Strangely enough, at the moment I actually feel satisfied, as if I ate dinner. I'm pretty convinced that a lot of the "hunger" we claim we feel is not true hunger, but just caused my hunger hormones the body is trained to release at the times you normally eat.
- I drank about a gallon of water over the course of the day and ingested some salts, and will try to keep that up throughout the fast. A pretty easy day. But a 1-day fast is always easy.

Day 2 - Aug 23
- 8:30 am: After a bit of internal debate this morning, I decided black coffee would be allowed on my personal fast. Time to start my second GRE practice exam.
- 10:30 pm: Super focused all day. After finishing the practice GRE, I got caught up in a task and next time I checked the clock it was 10:30pm. There has been no drop in my energy levels — in fact, I felt no afternoon slump at all which I sometimes do after I eat my first meal of the day. Fasting is a lot easier if you have things to keep you occupied. 

Day 3 - Aug 24
- 9:00 am: Feel great. 
- 4:40 pm: Absolutely no hunger, appetite, or drop in energy. Day 3 of a fast has always been quite difficult in the past, but not this time. I suspect that the ease of this fast so far is a result of my ketogenic diet proceeding the fast as well as my daily salt intake during the fast. 

Day 4 - Aug 25
- 9:00 am: Ditto 9 am yesterday.
- 4:40 pm: Have a minor stomach ache (could be related or unrelated to fasting, since I get stomach aches a lot), but otherwise ditto 4:40pm yesterday.

Day 5 - Aug 26
- 8:00 am: It's hard to believe it until you actually experience it, but at this point I feel great with absolutely real desire or need to eat anything. Due to my rib injury I am not doing any daily exercise, so I cannot confirm how I would feel if I went on a run, but I don't notice any feeling of weakness from lack of food.
- 10:30 pm: Kind of getting bored of not having food to break up the day, but other than that feel great. Lots of mental clarity and focus too.
- Interesting observations: The slight puffiness I've noticed in my arms and legs has decreased; this is most likely due to not consuming any carbohydrates for five days (carbs naturally retain water in the body). Also, I have an old tick bite that has been inflamed and itchy all summer, but just in the last five days, the redness and itchiness as pretty much disappeared. This suggests an overall reduction in background inflammation in my body.

Day 6 - Aug 27
- 9:00 am: Slept in until 9am! Yikes. (I normally get up around 5am.) I'm getting a lot more sleep than usual this week but I suppose this week is a nice rest and recovery period for my body, which has been pushed pretty hard all summer. Had a minor muscle cramp last night, probably due to not intaking any salts these last few days. I'm drinking some electrolytes now, which should take care of it. Otherwise, feel great—lots of mental focus and clarity and my abdomen feels light and refreshed.
- 2:00 pm: Laying out in the sun working on this trip report. The nice weather is making me antsy to climb....I think it is harder for me not to be out climbing than it is to fast....perhaps one of the main benefits of this fast at this point is keeping me from doing something stupid and re-injuring my rib....
- 6:30 pm: These last few hours were—unexpectedly—probably the hardest so far. Felt weak for the first time since I started this fast, and was finding it difficult to focus on anything but food. Probably too much caffeine on an empty system (my electrolyte powder contains caffeine, plus I had a coffee and a diet coke). But I rode it out and I feel fine again now.
- 10:20 pm: I've noticed my urine smells fruity, which is a sign that I'm burning fat for fuel, i.e. ketosis. Makes me wonder if my earlier jitters was my body finally running dry on its stored glycogen.

Day 7 - Aug 28
- 3:50 pm: Been a busy day driving back to Bellingham from my parents' place, doing errands, and now headed to the campus to move my office to a new room. Haven't even had time to stop for coffee. Easiest day of the fast so far!
- 8:40 pm: Going to bed, as I got to get up early to drive to Montana. I've emptied my car's snack bin of anything with significant carbs, and filled it with jerky, salmon packets, cheese, and nuts and got the cooler packed with leafy greens. Hey, I get to eat tomorrow!


This fast was almost too easy! (But I am not complaining of course, just a bit surprised.) The hardest part was the boredom of not eating or having meals to break up a day. After the first day, I didn't really struggle with hunger and I had no significant drop in energy level the entire 7 days. I attribute the ease of this fast to the ketogenic diet I've experimented with this year—my body has become used to burning fat for energy, and this fast has been evidence that it doesn't really distinguish between dietary and body fat. I also suspect my daily salt intake (following the Snake Juice recipe of 1 tsp potassium chloride (No Salt), 1/2 tsp sea salt, and 1 tsp baking soda) has helped keep the energy levels up, since electrolyte balance is linked to energy levelsI honestly don't think I would have a problem fasting for a few more days, but I have a climbing trip planned (fingers crossed the rib is ready!) so I will stop the fast at 7 days. And my taste buds are getting bored.
• There is definitely a difference between "fasting" and "starvation." When fasting, the body is running off its energy stores (first its stored glycogen reserves, which typically provide 1-3 days worth of energy, then body fat once it runs out of the stored glycogen). The reason I felt so good during the fast was that I was running off my own body fat, which—even for a thin person like me—offers several days worth of energy (see the number-crunching in the next section). If I were to continue the fast for a month or so, I would eventually run through my fat stores and start burning muscle. At this point, my body would be in starvation mode, and I'd probably feel quite weak and awful.
• The key for me was to keep occupied. Eating is such a normal routine that is hard to not think about food when you are sitting around with nothing to do and haven't eaten for several hours (or days!). But with the lack of hunger and the increased mental focus I had during the fast, if I was occupied several hours could go by without even thinking of food. I really do relish the productivity I have during fasting.
• Another observation is my need to keep constantly hydrating during a fast. Not only is drinking liquids the closest thing you get to actually eating and dispelling hunger, but staying hydrated keeps the energy up and helps keep flushing toxins out of the body. Without carbohydrates in the system to retain water, liquid moves pretty quickly through me (this applies for when I am on a ketogenic diet as well). 
• After 7 days of not eating, both my mind and body feel refreshed. Sort of like how a car runs after its gotten a tune-up, or how a vacuum operates after you've emptied the vacuum bag and cleaned the filter. 
• After all of this up-front effort, I am now quite a bit more determined to stick with a clean diet and specifically a ketogenic diet. I want to maintain this "feeling awesome" feeling now that I have it back! As planned, this 7-day fast was a nice kick-start back into the ketogenic lifestyle.
• How is my rib injury doing after over a week of inactivity? One of my worries for the timing of this fast is that because of the lack of incoming protein my rib injury would heal slower, but on the other hand, the reduction in overall inflammation of my system (evidenced by the less itchy tick bite) might help with healing. Who knows. In either case, at the end of my fast, my injury still hurts, but not as bad as it did. I can only hope that this period of rest has been enough to keep the injury to a dull roar for the rest of the season. When I go back to teaching in late September, it will be much easier to lay off it.
And, because I know people are curious, how much weight did I loose during this fast? And you will be disappointed to hear that I never once weighed myself, before or after the fast. I did feel a bit lighter on my feet after seven days of not consuming any food, but I do know that most weight loss from a fast like this is from water (carbs cause the body to retain water, so during a fast a lot of the extra water in the tissues is expelled) and feces (the intestines become refreshingly empty). But I can approximate that I lost about 3 pounds of body fat. How'd I get this number? Well, I figure with my inactivity during the fast and the fact that I am a pretty small person, I was burning about 1,500 calories a day during the seven days of fasting, which equates to 10,500 total calories; since a pound of fat is 3,500 calories, this equates to just 3 pounds of fat. (All that for just 3 pounds! Clearly, fasting is probably not worth it as a weight-loss technique. If I really wanted to loose weight, I'd rather just eat less and exercise more and loose weight a bit slower but enjoy life a bit more.) 
• After an extended fast like this, I suppose you should ease back into eating with easy-to-digest foods. Not heeding this advice, the first food I ate was two large packages of beef jerky. I had no issues. My digestive system picked right up where it left off, feeling even better than before the fast.
• I did consume coffee and flavored drinks on this fast. My only strict rule was no calories. Someday I'd like to do a water-only 7-day fast, which I think could offer even more healing benefits as the body gets a chance to detox more completely. I just need to convince my taste buds not to die of boredom!


OK, and finally, the part of this report that fellow climbers and athletes might find the most interesting. How is athletic performance affected by fasting and keto?

From my experimenting with fasting and the ketogenic diet, my conclusion is that fasting and keto are definitely performance-enhancing tools for an athlete, specifically when it comes to endurance, where the body needs to be pushed for hours at a calorie deficit and still perform well. Below I give some anecdotal and scientific support of this conclusion.

Fasting: As I mentioned previously in this report, I have intermittant fasted for years, so on a normal day I often go up to 20 hours without eating before I have my first meal. As a result, my body is quite used to long stretches without incoming food, and hence needing to draw from its energy reserves (stored glycogen when I am eating carbs on a daily basis, or stored fat when I am on the ketogenic diet or burned through my glycogen stores). I suspect my body's familiarity with drawing from its own energy reserves has helped on big days in the mountains, when calorie output exceeds calorie intake. I rarely feel the need to eat food for energy on a climb, and despite the fact that I am often eating very little during a big athletic push, I usually experience unfluctuating energy throughout the day; I cannot remember the last time I "bonked".

Keto: Because the ketogenic diet deprives the body of carbs, it forces the body to use fat (through a process called ketosis) and protein (through a process called glycolysis) for energy. Once "fat-adapted," the body does not seem to distinguish between dietary fat or body fat, opening up a huge source of energy off your own body. It seems clear to me that being fat-adapted (or at least having the body trained to easily be in this state) is a performance-enhancing tool for an endurance athlete.

So, how about we crunch some numbers! (After all, I am a math teacher.) How long can a healthy body safely go without food? I'll use my own body as an example. Say I weigh 120 lb and have 18 % body fat; this means I have about 21.6 pounds of fat on me. But some of this fat is necessary for essential body functions and padding the organs; let's say I need 8% body fat for essential body functions (sources will vary on this percentage, anywhere from 3-12%). So this roughly gives me 10% of my body weight—12 pounds of fat—that is safely available for fuel. A pound of fat has 3,500 calories of energy, so 12 pounds of fat equates to 42,000 calories. At an energy need of 2000 calories per day, this is 21 days worth of fuel just stored on my body! And I am quite a thin person, so this number would be a lot higher for most people (in fact, here's a link to an article about a guy who went over a year without eating!). Not even a car can go 21 days straight without needing a fill-up. Clearly, the body has more than enough energy to fuel itself for a long push in the mountains. It's just a matter of being able to tap into that energy source. Fasting and the ketogenic diet are a way to train the body to be able to easily tap into this energy source.

And finally, a piece of anecdotal evidence: In July, I did a 22.5-hour 2-route day on The Diamond (CO) entirely fasted. In fact, I hadn't eaten since noon the day before, so by the time we got back to the car—and I did eat then, I admit I was pretty ravenous once I got started—I hadn't ingested any calories for 36 hours. All I consumed was electrolyte-enhanced water. And I felt just fine. Crazy, huh? 

And as a final note, as my disclaimer at the start of this page mentioned, fasting and the ketogenic lifestyle is not for everyone: it is challenging physically, mentally, and socially. But if you think you're up for the challenge and/or just curious to know how your body feels, give it a try!