There always seems to be some hype around one fad diet or another, but these days, it’s not a food plan that's all the rage – it’s an eating pattern. Intermittent fasting, also known as intermittent energy restriction, refers to various consumption schedules that cycle between voluntary fasting and non-fasting over a given period of time. Among these schedules include alternate day fasting, periodic fasting or what seems to be the most popular, time-restricted eating.
Even though many of us haven’t heard about intermittent fasting until recent years, fasting has been a practice throughout human evolution. Hunter-gatherers often went long periods without food, and fasting is incorporated into many religious and spiritual practices in Islam, Christianity, Judaism and Buddhism. While fasting claims to provide a wide range of physical benefits, it’s only sound to wonder whether it’s truly safe? We dove in to find out – read on.
There are three common types of intermittent fasting:
For many, the goal of intermittent fasting is weight loss, for as we all know, the fewer calories we take in, the more weight we lose (as long as we don’t overdo it during the eating periods). Yet, these eating patterns affect our bodies on molecular levels as well. When fasting, insulin sensitivity improves and levels of insulin drop, impacting our metabolism and making stored fat more accessible to burn. In addition, levels of Human Growth Hormone (HGH) increase dramatically, helping to boost muscle growth, strength, exercise performance and enabling us to recover more quickly from injury and disease. When in a fasted state, our cells initiate a cellular repair process, and gene expression changes to provide better longevity and protection against disease.1
Specifically, intermittent fasting has been noted to: stabilize blood sugar, increase resistance to stress, decrease blood pressure and cholesterol levels, improve resting heart rate, enhance brain health and memory, slow aging and improved longevity, promote brain growth, repair and function, regulate hormone levels, improve blood composition, decrease oxidative stress, enhance fat burning and weight loss, reduce hunger and sugar cravings, and offer results that mimic the beneficial effects of exercise. Wow! 2
In December of 2019, The New England Journal of Medicine published an article written by Dr.'s Rafael de Cabo, Ph.D. and Mark P. Mattson, Ph.D. stating that intermittent fasting triggers a “metabolic switch from glucose-based to ketone-based energy, with increased stress resistance, increased longevity and decreased incidence of diseases including cancer and obesity.” The effect of weight loss alone improves glucose regulation, blood pressure and heart rate, and improves the efficacy of endurance training and fat loss, especially around the abdomen. The reduction of calories is also associated with an increased lifespan and improved memory function. Clinical trials on both rats and humans show promising benefits in diabetes, cardiovascular disease, cancer, neurodegenerative disorders, asthma, MS and arthritis.3
Are there any risks?
While most studies show well-thought intermittent fasting plans to be safe, there are always risks associated with changing our routine. For one, adhering to such a strict regimen can be difficult, making it more challenging to participate in social activities such as dinner parties and family events. The risk of isolation or separating from community is significant, so it’s important to find ways to continue to maintain social connections within this eating plan.
Fasting can also cause irritability, fatigue and periods of low energy, thus making it more challenging to function throughout the day. These symptoms typically pass within one month, but the practicality of maintaining a fasting regimen over time is something to be considered. Making sure to stop eating as early is possible (no later than 9 PM) is recommended so that our sleep cycles don't get disturbed.
There’s also the risk of overdoing the eating portion of the regimen. Hunger may start to feel so severe that we might have an urge to cram a ton of calories into our eating windows, ultimately paying less attention to the nutritional value of foods and more to the simple replenishment of calories. In this way, it’s possible to eat a less healthy diet and more calories than if one were to consume three square meals per day. The recommendation is to continue to select well-balanced meals during eating periods, with healthy amounts of good fats, proteins, fiber and produce.
When fats are used for energy, they produce ketone bodies that “regulate the expression of the activity of many proteins and molecules known to influence health and aging.” This state of ketosis is one that the Keto and Atkins diets aim to achieve. However, when taken to extremes, ketosis can damage the liver, kidneys and brain, making those with diabetes and heart disease particularly vulnerable.4
Because weight-loss is common while intermittent fasting, those who are already struggling to keep weight on (due to medical treatments or eating disorders) might not be healthy candidates for fasting. While there is evidence that fasts and calorie restriction can slow and even stop the progression of cancer, kill cells, boost the immune system and significantly improve the efficacy of chemotherapy and radiation treatments, it’s essential to take into account our overall well-being and consult with a doctor before embarking on a new eating schedule.5
All in all, intermittent fasting is an interesting and compelling approach to weight loss with strong anecdotal evidence pointing towards many other health benefits, but as with all new things, it’s something to ease into gradually. Instead of going full-force into the 16/8 Method, for example, consider starting with 12 hours of fasting and a 12-hour eating window. Then, build to 13/11 and 14/10, etc. There’s some debate around whether black coffee or tea is permitted during fasts, but for those with a love of their morning beverage, consuming calorie-free drinks can also make the transition easier.
“Fasting is the first principle of medicine; fast and see the strength of the spirit reveal itself.” Rumi