Dr. Randi Fredricks, Ph.D. is a therapist, researcher and author with a Ph.D. in Psychology and a Doctorate in Naturopathy. Dr. Fredricks works ...Read More
A number of books have come out in the past year discussing the advantages of intermittent fasting (IF) for weight loss. In fact, IF has been used to lose weight for well over a hundred years. Its efficacy has been documented in numerous studies published in peer-reviewed journals. A recent scientific review from Aston University examined clinical IF trials found that it can be helpful for individuals with diabetes, cardiovascular disease, and obesity.
IF is a pattern of repeated fasting and refeeding that alternates between periods of fasting (which typically means the consumption of water only) and eating. Alternate day fasting (ADF) is a form of IF that is a 48-hour routine most commonly composed of a 24-hour fast followed by a 24-hour non-fasting period. IF and ADF proponents have created endless variations from a 36-hour fast alternating with a 12 hour feeding window to doing a 24-hour fast twice per week. These types of intermittent fasting have been shown in trials to be as effective as or more effective than counting calories every day to lose weight.
Evidence from several studies found that fasting can reduce inflammation, alleviate hypertension, lower cholesterol, and improve levels of sugars and fats in circulation, reversing type 2 diabetes in some people. Fasting can also help people with ischemic heart disease, increasing levels of adiponectin, a protein that promotes healthy function in lipid metabolism and vascular biology. The studies have shown that a fasting body selects which fuel to burn through a process called autophagy, improving metabolism and reducing oxidative stress.
For the Aston University study, the researchers evaluated the various approaches to IF in the scientific literature. They searched specifically for advantages and limitations in treating obesity and type 2 diabetes using IF and other fasting diets. The researchers concluded that IF appeared to have the same benefits as bariatric surgery, but without the high costs and serious health risks associated with surgery.
As mentioned earlier, IF has become increasingly popular as a mainstream diet over the past few years, with numerous bestselling books claiming the newest and greatest IF diet plan. Interestingly, a number of the diet plans in these books do not involve any kind of real fasting and are actually just typical calorie restriction diets.
IF has come under criticism after research using rats indicated that extended periods of IF can be harmful to the heart. Meanwhile, other research has suggested that short-term IF has a helpful effect on the heart. The determining factors as to whether IF may be helpful or harmful include the patient’s health at the start of treatment and the level of supervision received. Additionally, studies have indicated that IF is most problematic when refeeding periods are too short and there is insufficient caloric intake between fasting periods.
Research has suggested that people using IF versus continuous calorie restriction tend to lose the same amount of weight. Other studies have found that changing meal frequency in any way (eating either more or less often) has virtually no impact on weight loss. People who lose weight with IF do so because they are experiencing a caloric deficit and the amount of weight they lose in the long run is dependent on the size of that deficit. Perhaps the best reason to choose IF over a typical calorie restriction diet is the purported health benefits.
Brown, J. E., Mosley, M., & Aldred, S. (2013). Intermittent fasting: a dietary intervention for prevention of diabetes and cardiovascular disease? British Journal of Diabetes & Vascular Disease, 13(2), 68-72. doi: 10.1177/1474651413486496
Fredricks, Randi. (2012). Fasting: An Exceptional Human Experience. Bloomington, IN: Authorhouse. ASIN: B00BN9NUI6