By Elliot Fisher MS, ATC, CSCS, PES
Fasting and intermittent fasting have become trending topics in the fitness community over the past years. There are many in favor of the idea of fasting and a lot of people against the idea. In this article, we’ll cover some of the pros and cons of fasting.
There is a lot of research looking at the health benefits of fasting. Going a prolonged period of time without eating helps with cell autophagy, increased insulin sensitivity, improves heart health, and assists in weight loss.
Cell autophagy is the process in which the cell gets rid of unnecessary or dysfunctional components.(1) This process occurs naturally and is how our body maintains itself overtime. When we fast there’s an increase in cell autophagy that helps keep the body healthy and functioning.(2)
Type II diabetes is a common disease in the 21st century. Diabetes is impacted by insulin sensitivity. After chronic exposure to excess glucose the body begins to weaken its response to insulin, causing an increase in blood sugar. This uncontrolled blood sugar is diabetes. Fasting helps the body become more insulin sensitive by decreasing the total number of carbohydrates and calories we intake.(3) This helps the body resensitize to glucose.
Heart health is the number one cause of death in america. Fasting improves cardiovascular function such as blood pressure and adaptation of the cardiovascular system.(4) High blood pressure is a huge contributor to heart disease and anything that can help manage hypertension is a great health benefit.
Bodyweight is a huge contributor to chronic disease even when body fat percentage is low. Obesity is never healthy. There is controversy regarding how unhealthy it is to have a BMI in the overweight category. Fasting helps lower total caloric consumption which helps with weight loss. This helps by limiting the hours you can be eating food as well as it helps decrease your appetite, reinforcing the lower caloric consumption.
Some research shows increases in different hormones with fasting. Two hormones of mention are growth hormone and testosterone. It’s shown that when longer fasts are done growth hormone secretion increases.(5) Growth hormone is important for metabolism, connective tissue health, sleep health, and many other functions in the body. Testosterone is also shown to increase. One study showed an increase by 180%.(6)
Most people in the fitness community want to look better. This typically means to have more muscle and less fat. Building muscle is a long arduous process. When trying to build muscle it is important to eat multiple meals throughout the day in order to stimulate muscle protein synthesis over and over again. Anywhere from 3-6 meals is usually a good recommendation. With intermittent fasting, usually only 1 or 2 meals are consumed. If more are consumed it is still done relatively close together which may not be the best for building muscle. Also, the long period of time without food may increase the amount of muscle catabolism (muscle breakdown) that occurs when fasting due to no available amino acids in the bloodstream.
It can be very hard to carry out your typical social obligations when doing intermittent fasting. You have to make sure if you are going somewhere to eat with friends, family, or work that you go during your eating window. Otherwise you will have to go and not have anything to eat, or break your fasting protocol. This can be a major drawback to people who want to go out often.
Fasting compared to Caloric Restriction
Fasting has numerous health benefits. The drawback here is that most if not all of these benefits occur when calories are controlled regardless of eating window. The biggest difference here is that fasting tends to decrease appetite and eating frequently can cause some people to have an increase in appetite.
There are both positives and negatives to fasting. Fasting is a great idea if you don’t find it overly challenging, if it helps with your appetite control, if it is conducive to your lifestyle, if weight loss and not building muscle is your main objective.
Mattson, M. P., Longo, V. D., & Harvie, M. (2017). Impact of intermittent fasting on health and disease processes. Ageing research reviews, 39, 46-58.
Barnosky, A. R., Hoddy, K. K., Unterman, T. G., & Varady, K. A. (2014). Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. Translational Research, 164(4), 302-311.
Mattson, M. P., & Wan, R. (2005). Beneficial effects of intermittent fasting and caloric restriction on the cardiovascular and cerebrovascular systems. The Journal of nutritional biochemistry, 16(3), 129-137.
Hunter, W. M., Willoughby, J. M. T., & Strong, J. A. (1968). Plasma insulin and growth hormone during 22-hour fasts and after graded glucose loads in six healthy adults. Journal of Endocrinology, 40(3), 297-311.
Röjdmark, S., Asplund, A., & Rössner, S. (1989). Pituitary-testicular axis in obese men during short-term fasting. European Journal of Endocrinology, 121(5), 727-732.