At Parsley Health , we have helped hundreds of our patients with weight loss and healthy weight management. Carrying around excessive weight can be troubling on multiple levels. Not only can it be an emotional struggle; but it also makes just about any medical condition harder to deal with. As holistic-minded physicians, we don’t necessarily view weight loss as an aesthetic goal as much as it is a way to dramatically reduce inflammation .
Although it’s a fantastic perk to see our patients happy with how they look, it’s even more incredible to see how weight loss can affect someone’s emotional state and disease progression. Excessive adipose tissue, or fat on the body, is highly inflammatory, and that leads to worsening of just about every medical condition. It also causes insulin resistance, catecholamine resistance, and estrogen excess (6). These issues have negative impacts on one’s entire body, including their metabolism, mental health, reproductive system, and hormones.
Restricting calories by eating less food, and changing the types of foods that one is eating, are methods that people usually use to achieve weight loss. While these methods may work for many, they can frequently leave others feeling hungry, frustrated, and ultimately at the same (or sometimes even higher) weight. Another method of eating, called intermittent fasting, has been getting a lot of attention in the past several years. Not only are people using this technique for body fat trimming, but also for mental stimulation, anti-aging effects, anti-cancer effects, even spiritual enlightenment, and more.
One reason for this more recent increase in interest in fasting may be due to the 2016 Nobel Prize in Physiology or Medicine winner, Yoshinori Ohsumi, who discovered the connection between Alzheimer’s disease and lack of autophagy. Autophagy is the process by which cells capture large dysfunctional proteins, aging cell components, and invading pathogens into packages to be disposed of (7). Autophagy not only has activity against Alzheimer’s disease but also fights cancer cells. The process of autophagy can be activated by fasting, which implies that fasting can be used to prevent and treat Alzheimer’s disease and cancer.
Fasting is the overall abstinence from consuming food. The length of time that people choose to fast is variable, depending on the goals that they are trying to achieve. Fasting is an incredible tool for weight loss and body fat break down. When the body is not receiving an input of food, the body is forced to break down fat in order to survive and fuel the body. It’s a fairly simple concept that we, as a modern society, have not been using very much until more recently. The premise is that, regardless of whatever diet one might be told will cause them to lose weight, if you’re still consuming food, then the body is not being given a signal to break down its own fat for fuel.
I’ll address a few common concerns about fasting here that might help you decide whether this is right for you. It’s best to have a healthcare practitioner to work with when starting any new nutritional plan, but fasting can also be done safely by oneself if given the right information.
First, the concern has been raised that if one does not eat food for an entire day, for example, then the basal metabolic rate of the individual will decrease. However, research has shown this not to be the case. A study compared alternate day fasting (eating every other day) to daily caloric restriction (400 calories less than usual). After 8 weeks, the metabolic rate in the caloric restriction group fell 6%, while it only fell 1% in the alternate day fasting group, although the same amount of weight was lost. After 24 week follow up, the caloric restriction group still had a lower metabolic rate by 4.5%, while the alternate day fasting group had maintained their normal metabolic rate (1).
Another study on 11 participants (7 women and 4 men), showed that resting energy expenditure actually increased after 3 days of fasting. This is attributed to the increase in adrenaline that accompanies fasting (3). In response to lower blood glucose levels, adrenaline is released to mobilize glucose from the liver and eventually fat cells. This also gives people a boost of energy and mental focus. It’s for this nootropic effect that many execs in Silicon Valley have been joining the fasting bandwagon as well (4). Therefore, it appears that alternate day fasting could be a powerful and safe tool to achieve weight loss and mental focus, without decreasing one’s metabolic rate significantly.
Secondly, another concern that people have about fasting is the hunger that one might experience. Interestingly, when comparing intermittent fasting versus calorie restriction, is has been noted that the hunger response is more pronounced when on a calorically restricted diet than in fasting (5). In a 10-week study done on alternate day fasting for weight loss, it was found that after 2 weeks, the hunger response decreased significantly and continued to stay low (2).
Lastly, there is a common concern that one might start breaking down muscle while fasting. Fortunately, this is not the case, due to the body’s incredible adaptive response to fasting.
There is a common concern that one might start breaking down muscle while fasting. Fortunately, this is not the case, due to the body’s incredible adaptive response to fasting.
Humans were never subject to constant and abundant food supply in the history preceding the agricultural revolution around 80 years ago. Before this, there were intermittent forces of nature causing food to become scarce for periods of time. The people who survived these eras passed on their advantageous genes. During periods of fasting, the brain actually releases more human growth hormone (HGH) which helps preserve lean muscle mass in men and women (8). A study done in 1992 on 9 men showed that HGH production rate increases 5-fold after a 2 day fast (9). So fasting can essentially cause increased fat loss while preserving your muscle mass. It’s for this reason that many athletes are now adopting fasting into their training routines (10).
If you’re interested in trying out this eating method, I think it’s a good idea to start slow. Try abstaining from eating for a 16 hour window, for a day or two per week. This can generally be done by skipping one or two meals. Then try to extend it to 24 hours and see how it feels. It’s important to remember that the types of foods that you eat on feeding days do matter. At Parsley Health, we recommend specific foods to eat in order for our patients to achieve their health goals as well. This is something to discuss with your doctor and health coach as they guide you through this process.
Here are few pointers in order to make your intermittent fasting experiment more successful. First of all, it’s good to do this at a time when you’re not traveling, and you can control your environment. For hydration during periods of fasting, it’s advisable to drink plenty of fluids. Depending on the length of time, some may do well to use electrolyte tabs in their water, drink unsweetened teas or coffee, drink bone broth, or even eat some coconut oil, depending on the situation. Taking a multivitamin every day can ensure one’s overall nutrient status is stable throughout. Detoxifying supplements like magnesium or glutathione could further enhance the body’s ability to get rid of unnecessary junk during fasting as well.
Fasting doesn’t mean not drinking. Staying hydrated is critical.
It’s important to know certain situations where fasting of any kind is not advisable. Pregnant and breastfeeding women should not fast, due to the nutrient demands of the developing child. Underweight people should not fast, as it could cause dangerous levels of further weight loss. People with a history of eating disorders should take precaution with fasting, as it may lead to overall emotional and restrictive eating. Lastly, it’s not advised to do a complete fast without drinking liquids and taking electrolytes. Some may choose to do a complete fast for religious reasons, but from a health standpoint, it is not advisable, especially when doing more extended periods of fasting.
In preparation to write this article, I decided to try fasting for myself. I encountered countless research, articles, and podcasts proclaiming the health benefits of fasting. Not only for fat loss, but for it’s anti-aging, anti-cancer, and mentally stimulating effects. Additionally, if I am recommending something to my patients, I like to have first-hand experience with it in order to better guide them.
Last week, I did a 16 hour fast by skipping breakfast . I found the mental stimulation to be quite palpable, and the hunger to be tolerable. Over this weekend, I did a 38 hour fast, and although there were periods of hunger which I controlled with coconut oil and electrolyte solutions, it was also not as difficult as I had predicted. Luckily, due to loads of research coming out regarding its health benefits, it’s not as socially awkward as it maybe once was. I actually went to a barbeque and was totally fine socializing there with friends. I plan to incorporate some form of fasting into my weekly routines going forward.
For more information, I recommend reading the Complete Guide to Fasting, by Dr. Jason Fung, a Canadian nephrologist. He has done extensive research in the area of fasting and decided to write a manual on fasting because it was previously non-existent. Fasting has been an extremely powerful tool for many of his own patients to effectively treat, and sometimes cure, type 2 diabetes, high cholesterol, high blood pressure, obesity, and more.
1) Obesity (Silver Spring). 2016 Sep;24(9):1874-83. doi: 10.1002/oby.21581.A randomized pilot study comparing zero-calorie alternate-day fasting to daily caloric restriction in adults with obesity.
2) Nutr J. 2010 Sep 3;9:35. doi: 10.1186/1475-2891-9-35. Dietary and physical activity adaptations to alternate day modified fasting: implications for optimal weight loss.
3) Am J Clin Nutr. 2000 Jun;71(6):1511-5. Resting energy expenditure in short-term starvation is increased as a result of an increase in serum norepinephrine.
5) Clin Nutr. 2016 Dec;35(6):1380-1385. doi: 10.1016/j.clnu.2016.03.011. Epub 2016 Mar 30. Changes in hunger and fullness in relation to gut peptides before and after 8 weeks of alternate day fasting.
6) Adapting to obesity with adipose tissue inflammation. Shannon M. Reilly & Alan R. Saltiel. Nature Reviews Endocrinology 13, 633–643 (2017)