By Nikhil Kumar, Fall 2021.
Chances are, whether on the internet or in real life, you’ve heard the words “intermittent fasting” or “IF diet” before. In my own life, I see those fitness buzzwords everywhere. Whether it’s my father who chooses not to eat anything during certain times of the day, my roommate who eats only one large meal a day, people on social media, or even actors on TV shows – intermittent fasting has blown up in the dietary trend space of popular culture. Given its popularity, I was interested in exploring some questions related to it. What exactly is intermittent fasting? How does it work? Who is it for? And most importantly, is it ultimately good for your health?
Intermittent fasting is essentially an eating pattern that cycles between periods of fasting and eating. Intermittent fasting, therefore, is a unique diet that places more emphasis on when you eat rather than what you eat. The most significant idea to keep in mind is that eating must be restricted to a certain period, while the rest of the time is for fasting, where no food is eaten. Since intermittent fasting is designed around an eating pattern, as opposed to a fixed diet, it’s extremely flexible and there are many variations on its execution. For example, one might fast for 16 hours each day and only eat during 8 hours of the day (around two meals) while another might fast completely for 1 or two days a week while eating normally for the rest of the days. Both are considered valid methods of intermittent fasting.[1]
While intermittent fasting may sound complicated and offers a diversity of implementations, the mechanism it relies on is simple and remains the same regardless of method. When food is consumed, part of it is converted to simple sugars to produce energy, while the rest gets stored as various molecules throughout the body, such as glycogen and fat. This storage occurs via the actions of the hormone insulin, which is usually produced after eating. By allowing time for fasting, insulin levels remain low for most of the day. Since less sugar is taken in and stored, glycogen and fat are required to be converted back into sugar for use in producing energy.[2]
Under our current understanding of intermittent fasting, this method of eating to burn fats produces numerous health advantages. Perhaps one of the most obvious advantages of intermittent fasting is its ease in burning fats and enabling weight-loss. Studies have shown that intermittent fasting has a substantial effect on reducing weight and fat content.[3] However, what gives it an edge over diets seeking similar weight-loss goals is the fact that it doesn’t require major calorie restrictions. If the time for fasting is maintained, fats will continue to be burned.[1]
At the same time, the advantages of intermittent fasting are not reserved to weight-loss. For example, intermittent fasting has been observed to increase the body’s sensitivity to insulin, which can reduce the risk of type 2 diabetes (a disease where the body is unable to reduce blood sugar levels). At the same time, it reduces the total insulin levels to make fats more accessible for breakdown.[3] Studies have also suggested that fasting can dramatically improve the secretion of growth hormone in humans, allowing for greater fat loss and muscle gains.[4][5] Reduced risk factors for cardiovascular (heart) disease and markers for inflammation have also been cited as benefits of intermittent fasting or fasting in general.[6][7] Additionally, after showing promising results in animal trials, research is ongoing into the potential advantages of intermittent fasting in relation to reduced risk of cancer and anti-aging properties.[8][9]
While the potential for intermittent fasting seems limitless, this eating pattern is not without its drawbacks. Most limitations stem from the individuals who undergo intermittent fasting themselves. For example, studies have shown that there is an extremely high dropout rate for intermittent fasting trials. People are either unable to keep up with this regimen and go without food for so long, or they end up overeating during the time they are not fasting. Apart from this, there are several claims that the potential benefits for intermittent fasting in humans are overstated since the trials in humans are few and even those have provided only limited evidence of benefits apart from weight-loss. As a result, intermittent fasting seems to not be quite as advantageous over other diets, as one might believe.[10]
Additionally, intermittent fasting is simply not a good option for everyone. In women, intermittent fasting has been shown to affect hormonal control and blood sugar levels. Therefore, it is recommended that women take care when pursuing intermittent fasting, especially when pregnant or trying to conceive. Intermittent fasting is also dangerous if the individual is underweight or has previously experienced eating disorders, since a lack of regular meals could exacerbate these conditions. Finally, people with diabetes or blood sugar control issues should not attempt intermittent fasting, since the body could have issues handling the drop in insulin during periods of fasting.[1]
Intermittent fasting has seen a massive surge in popularity in recent years. In 2012, documentaries like Eat Fast, Live Longer by BBC journalist Dr. Michael Mosley and books like The 5:2 Diet by journalist Kate Harrison kickstarted interest in intermittent fasting.[2] However, the reason for its massive popularity today is largely due to anecdotes about its effectiveness. These success stories, along with the simplicity of undertaking intermittent fasting, made intermittent fasting the extremely popular weight-loss option it is today. Its flexibility and potential benefits continue to make it an attractive option for the general population.[11]
From what has been described about intermittent fasting, it seems as though it could be a particularly good method of weight loss. Through various animal-based and observational trials, it’s been determined that there could be advantages beyond weight-loss as well. However, it is important to remember that intermittent fasting could possibly be damaging for one’s long-term health. What becomes abundantly clear from the fact that intermittent fasting has become popular through anecdotal instances and the lack of clear benefits in humans from research studies is that intermittent fasting comes down to the individual. As mentioned before, intermittent fasting could cause negative side effects for certain individuals like women, people with poor blood sugar control and those who are underweight. At the same time, for others, it could be a major step toward a healthier lifestyle.
[1] Gunnars, Kris. “Intermittent Fasting 101 – the Ultimate Beginner’s Guide.” Healthline. Healthline Media, April 21, 2020. https://www.healthline.com/nutrition/intermittent-fasting-guide.
[2] Monique Tello, MD. “Intermittent Fasting: Surprising Update.” Harvard Health, March 10, 2020. https://www.health.harvard.edu/blog/intermittent-fasting-surprising-update-2018062914156.
[3] Barnosky, Adrienne R., Kristin K. Hoddy, Terry G. Unterman, and Krista A. Varady. “Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings.” Translational Research 164, no. 4 (2014): 302-311.
[4] Ho, Klan Y., Johannes D. Veldhuis, Michael L. Johnson, R. Furlanetto, William S. Evans, K. G. Alberti, and M. O. Thorner. “Fasting enhances growth hormone secretion and amplifies the complex rhythms of growth hormone secretion in man.” The Journal of clinical investigation 81, no. 4 (1988): 968-975.
[5] Hartman, Mark L., Johannes D. Veldhuis, Michael L. Johnson, Mary M. Lee, K. G. Alberti, Eugene Samojlik, and Michael O. Thorner. “Augmented growth hormone (GH) secretory burst frequency and amplitude mediate enhanced GH secretion during a two-day fast in normal men.” The Journal of Clinical Endocrinology & Metabolism 74, no. 4 (1992): 757-765.
[6] Varady, Krista A., Surabhi Bhutani, Emily C. Church, and Monica C. Klempel. “Short-term modified alternate-day fasting: a novel dietary strategy for weight loss and cardioprotection in obese adults.” The American journal of clinical nutrition 90, no. 5 (2009): 1138-1143.
[7] Johnson, James B., Warren Summer, Roy G. Cutler, Bronwen Martin, Dong-Hoon Hyun, Vishwa D. Dixit, Michelle Pearson et al. “Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma.” Free Radical Biology and Medicine 42, no. 5 (2007): 665-674.
[8] Siegel, Israel, Tian Lin Liu, Napoleon Nepomuceno, and Norbert Gleicher. “Effects of short-term dietary restriction on survival of mammary ascites tumor-bearing rats.” Cancer investigation 6, no. 6 (1988): 677-680.
[9] Goodrick, Charles L., Donald K. Ingram, Mark A. Reynolds, John R. Freeman, and Nancy L. Cider. “Effects of intermittent feeding upon growth and life span in rats.” Gerontology 28, no. 4 (1982): 233-241.
[10]Harvard Health. “Not so Fast: Pros and Cons of the Newest Diet Trend.” Harvard Health, July 31, 2019. https://www.health.harvard.edu/heart-health/not-so-fast-pros-and-cons-of-the-newest-diet-trend.
[11]Brzyski, Laura. “Here’s Why Intermittent Fasting Is Suddenly so Popular in Philly, According to Nutrition Pros.” Philadelphia Magazine. Philadelphia Magazine, February 25, 2020. https://www.phillymag.com/be-well-philly/2020/02/25/intermittent-fasting-trend/.