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What Happens When You Don't Eat For 24 Hours Part 2


11am- this is now almost 16 hours into my fast experiment and I am definitely feeling the mental hunger. It is important to identify the difference between this and physical hunger. In my head I am thinking about food but my stomach isn’t growling excessively which is telling me I’m really not that hungry. I’m not low energy, and I’m certainly not about to keel over and die. I’ve done this 16 hour fast 8 hours eating experiment before, fairly consistently in fact so this is nothing new to me. The real key is to keep busy. A lot of people eat out of boredom. To keep myself busy I bought the book Switch by Dan Heath and Chip Heath, two good authors on change psychology. All the science I know on nutrition and exercise and all the programs and experience I have in the weight room are useless if I cannot get people to change their habits. This is where books like this become particularly important.

I think I’ll do a little catch up on The Walking Dead as well; season two just came out on Netflix. By the end of the day I may feel a bit like a zombie myself. It happens when you don’t eat for that long. You start to move around a little less/slower, anything to conserve energy, you get a little sluggish, and you begin to have an insatiable appetite for human brains. Okay that last part I made up just making sure we’re all still paying attention here.

At 12 o’clock I had my second servings of greens supplement and branched chain amino acids. I also had my third cup of coffee which will be it for me today. That along with excessive quantities of water has made bathroom trips fairly regular.

It is now about 1 o’clock and hunger levels are fairly nonexistent aside from me thinking about what I am going to have at 7:30 tonight, which once again is mental not physical.


I want to briefly go over the physiology behind hunger. We have orexigenic hormones, those that stimulate appetite and anorexigenic hormones, those that suppress appetite. I want to talk about Ghrelin, our appetite stimulating hormone, cholecystokinin, and Leptin a 167 amino acid protein that suppresses appetite

Ghrelin stimulates hunger we see levels increase before meals and decrease after meals. As mentioned earlier, fasting causes increases in growth hormone. Ghrelin mediates that process because it stimulates growth hormone secretion from the pituitary gland. . “Ghrelin is the only know gut orexigenic hormone” (Stengal and Tache, 293).

Cholecystokinin is a hormone produced in the intestines that responds to fat by contracting the gall bladder and releasing bile, bile works to break down fat. It also helps to produce digestive enzymes. “Circulating levels of ghrelin are affected by a variety of gastrointestinal hormones and neurotransmitters. A reduction of ghrelin plasma concentrations is induced by cholecystokinin” (Stengal and Tache 298). These two substances have a checks and balance system if you will. When you’re not eating and hungry ghrelin is produced and tells your body to eat. Once you do eat cholecystokinin is released it reduces circulating ghrelin and inhibits it as well.

Leptin, the 167 amino acid protein, inhibits appetite. Extremely low calorie diets such as what I am doing right now can lower leptin levels and it is not recommended that people do what I am doing more than once per week. Elevated levels of leptin have been recorded in obese patients as well as in animal models suggesting the possibility of leptin resistance where more leptin is needed to get the job done. This doesn’t seem out of the question, it happens with insulin the fat accumulating hormone. When we have a consistently poor diet and higher levels of insulin are released we eventually need more insulin to get the job done. This is common in pre-diabetics. Leptin and cholecystokinin work hand in hand; in a study where leptin was “injected intraperitoneally at a subthreshold does,” it “induced a rapid in onset reduction of food ingestion when simultaneously injected with a subthreshold dose of cholecytokinin-8 whereas alone leptin had no effect” (Stengal and Tache, 298).

1:30- mental levels of hunger have subsided, keeping busy writing and studying the effects of different hormones on the body is doing the trick although it’s about as much fun as when I used to sit through my calculus lectures in college. At this point my levels of physical hunger aren’t really existent either. This is only 18 hours in though, still 6 more to go. Jason Krupka asked me at around noon to go to the Syracuse women’s ice hockey game and then to the weight room. I had planned on removing myself from society today in fear that I would turn into a miserable jerk but I decided to go. Hour 20 is where it should get really interesting but by then I will have removed myself from any temptation by being at the hockey game which is at 4 and after that I will be putting myself through further experimentation because at around 6:30 or whenever the game lets out we will go to the weight room to do some sprint intervals with circuits and Olympic lifts.

3:00- I had my last servings of greens supplement and branched chain amino acids and headed out to the Syracuse women’s ice hockey game. After the second period I headed over to the weight room at Syracuse and did some snatches then sprint intervals with a complex in between. While physical hunger still wasn’t really bothering me I could definitely tell that I was low energy. I only did half of the sprints that I did two days ago realizing that if I continued hunger would either consume me or I would pass out. Either way, after 20 hours of not eating I was not feeling bad or even that hungry but I definitely could not produce 100 percent effort on sprints or Olympic lifts.


I’ve lifted weights in the morning without eating, running on a 14-15 hour fast with no real affect on my performance; in fact I’ve had some of my best Olympic lifts in a fasting state. However, I have never exercised on 22 hours without food. I felt as if it negatively affected my performance, but perhaps there are some benefits to doing this once in a while? Also I would like to note that the results of my lift might have been different if I was doing strength training instead of sprints which were prolonged to 25 seconds followed by a short complex of hang cleans x3, overhead press x3, back squat x3, stiff leg deadlift x3, and bent over rows x3. I’m sure my lift would still have been negatively affected if I did a max bench press, deadlift, or squat, but to what degree? So in looking for the positives of exercising in a fasted state I went to do some research. I had already hypothesized that my body would be more receptive of carbohydrates after fasting, in fact my body would probably be screaming for them as is the case post workout, your body uses carbohydrates to spike insulin levels which helps with protein and glycogen synthesis in the muscles (if your muscles are insulin sensitive).

First thing we need to know is how the body uses different sources of energy. At low intensity exercise the body will use fat and at higher intensity exercise the body will use carbohydrates for energy, still following? Good, now understand that your body loves carbohydrates absolutely loves them.

How much does you body love carbs? See video and replace corn bread with carbs

While there are carbohydrates/glucose in the blood stream your body isn’t going to pay any attention to fat, and since it’s safe to say that I don’t have any carbohydrates in my blood stream fats going to get a lot of attention. “It is well established that high exogenous carbohydrate availability markedly suppresses the rate of fat oxidation during exercise” (Coyle et al. 1997). So I should assume that I’m hopping aboard the fat burning train right? Whoop whoop! Well, only kinda sorta; we need to look at fat burning on more of a 24 hour continuum, so yes while you exercise you burn fat but due to hormonal and enzyme activity that will eventually switch over, unless of course you haven’t had carbs or any other fuel . So I had been going through my fat stores during the day and amplified this process during exercise. I’ll bring it up later but it’s not a bad idea if you want to burn fat to wait to eat 30-60 minutes after exercise.

 “It has been shown that glucose ingestion during exercise blunts muscle hormone-sensitive lipase activity, the rate limiting enzyme of intramuscular triglyceride lipolysis” (Watt et al. 2004b). Hormone sensitive lipase is the enzyme that breaks down triglycerides in our fat cells and turns them into free fatty acids that our muscles can use. When I was at the National Strength and Conditioning Association in Providence Rhode Island this year I got to talking with a supplement rep from Generation UCAN which created a carbohydrate supplement with a minimal insulin response. What are the implications for this? Your body get’s those carbohydrates they love; see above video if you forgot how much your body loves carbs, while fat burning can continue. When insulin levels are spiked hormone sensitive lipase activity decreases but since insulin levels don’t spike your body gets its favorite form of energy and is still burning fat.

In a study on the effects of fasting on endurance exercise two important facts were discovered. Before I go over what was found here are some details of the study. The study took cyclist in a fasted state (they hadn’t eaten in the morning yet) vs cyclist who were given a carbohydrate solution. They then cycled at submax rates for two hours and were given a carbohydrate solution for recovery after. The first bit of information that was found that “the increase in plasma insulin associated with oral carbohydrate loading during recovery was markedly greater in fasting than in the carbohydrate group” (De Bock, Richter, Russell 654). This to me just backs up the notion that your body is more ready to accept nutrients after a fasted state. I would like to re-note however that for those of you looking to burn fat you might want to hold off an hour after exercise to eat so that the free fatty acids you released from fat cells may be burned. If we get that immediate insulin spike after exercise the free fatty acids will return to fat cells. The second bit of information was that “the effect of prolonged endurance exercise of markedly stimulating intramuscular triglyceride breakdown in type 1 fibers in the fasted state can be completely inhibited by a high rate of carbohydrate intake before and during exercise” (De Bock, Richter, Russell 656). They found that in our slow twitch fibers that triglycerides were broken down considerably more than in the carbohydrate supplement group. Also another great reason to try UCAN, have energy and burn extra fat.

While this is a study on an endurance group of exercisers and while this may be applicable to many readers we can assume that a similar fat burning effect can occur with weight lifting and that to amplify its fat burning effect we can wait 30-60 minutes after exercise to begin eating. Since I was about 22.5 hours into my fast when I finished my training I had another hour and a half of magnified fat burning.


7:30- Well that was surprisingly easy and now for the fun part. 24 hours had passed and I had just exercised. I got home and got to cooking, protein whole wheat pancakes with walnuts, bananas, cinnamon, blueberries, and dark chocolate chips with peanut butter on top- fantastic. After the combination of food deprivation and exercise your body can handle food like this a little better, not the best food choice though as you can tell. I also had chicken breast and a whole big plate full of vegetables to add something good to the mix. Okay I had three Sam Adams Octoberfest beers as well, whoops! I rarely drink but I enjoy something new in moderation once in a while.


Weight this morning-190.6

Is there some lesson that I can take out of this and relay to the reader, yes there is. Did I come up with some revelation during hour 22? Nah probably not, but it gets you thinking about all the things we can do without. If I can do without food for 24 hours can I go without spending money for 24 hours? Can I go without using technology, i.e. my phone or the internet for 24 hours? We eat when we don’t need to eat, we spend money we don’t have, and we waste time we don’t have. So if you’re not interested in trying a food fast maybe try a technology fast, turn off your phone and don’t check your emails for 24 hours. It will make you realize there are a lot of things we can go without.





Jessen, A., Buemann, B., Toubro, S., Skovgaard, I., & Astrup, A. (2005). The appetite-suppressant effect of nicotine is enhanced by caffeine. Diabetes, Obesity & Metabolism, 7(4), 327-333

Stengal A. & Tache Y. (2011). Interaction between gastric and upper small intestinal hormones in the regulation of hunger and satiety: Ghrelin and cholecystokinin take the central stage. Current Protein and Peptide Science, 12, 292-304.

De Bock K, Richter E, Hespel P, et al. Exercise in the fasted state facilitates fibre type-specific intramyocellular lipid breakdown and stimulates glycogen resynthesis in humans. The Journal Of Physiology [serial online]. April 15, 2005;564(Pt 2):649-660. Available from: MEDLINE with Full Text, Ipswich, MA. Accessed October 7, 2012.


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