Does Intermittent Fasting Work and Is It Safe?
And, you would be right to wonder. It is important before you embark on such a regime that you have confidence in the system, and that you believe it will work for you. To address this concern, I can offer two thoughts. Firstly, not only have I benefited through this regime myself, I have also helped hundreds of direct clients, and many thousands of readers of my blog, all achieve their best condition ever. This is a program that works for all types of body. Secondly, and just as importantly, the program of intermittent fasting that I describe in this book is supported by compelling, well-conducted, and published scientific evidence. Intermittent fasting is not a fad or a craze dreamt up without basis in fact, but a regime that is founded on hard science. The purpose of the following chapter is to present and summarize the scientific literature that is available regarding the benefits of intermittent fasting, and to allow you to draw your own conclusions. I feel strongly that it is important for you to be satisfied with the science and convinced by the data before you begin your own regime. The studies discussed in the sections below have been identified by a comprehensive search of the literature. They are not studies that have been selected because they fit a particular thesis. The full reports of many of these studies are freely available online to any reader with an interest in exploring the subject further. If the full paper is not available free of charge, a summary (or “abstract”) of the paper almost certainly will be. A significant proportion of people who embark on a program of intermittent fasting undoubtedly do so in order to achieve a reduction in body weight. And, this is a perfectly reasonable goal in its own right. However, you will find as you progress with your regime that a number of other health benefits become apparent. For example, you may find that you have more energy, that you suffer fewer coughs and colds, and that you feel generally in a better state of health. There are a number of further advantages to this program which may not be immediately noticeable but which will improve your underlying health in general. For example, data show that intermittent fasting has positive effects in terms of cardiovascular health, neurological function, protection against disease, insulin sensitivity, and hormonal responses. The scientific evidence to support the benefits of intermittent fasting in these different areas is discussed over the following sections.
A systematic review of the four studies discussed showed that intermittent fasting was effective for short-term weight loss. However, there was increased variability in our included studies, ranging from 16 to 334 participants with a follow-up period ranging from three weeks to 104 weeks ( Galani C, Schneider H., 2007). Baseline characteristics of the study population were also different in terms of body mass index which included normal weight subjects, overweight and obese subjects. Mode of interventions was also different for each individual study. A systematic review by Davis et al. found that dietary plans had significant weight loss in intermittent fasting groups. Seimon et al. in his systematic review found that intermittent fasting diet was as effective as daily restriction of calories both for short and long-term interventions. Most common issues with continuous calorie restriction diet are that restriction of food continuously is a trigger for higher hunger and additional eating. In these situations, ADF is a better solution which might be an optimal solution so that people can eat in their usual ways on non-fast days. This also depends on the type of the ADF used which minimizes the fatigue associated with continuous calorie restriction.
In addition, research is needed to test whether these regimens can complement or replace energy restriction and if so, whether they support long-term weight management.
Relationship of metabolic risk factors and development of cardiovascular disease and diabetes. Haffner SM. Obesity (Silver Spring) 2006;14:121–127.
Prevention and treatment of obesity with lifestyle interventions: review and meta-analysis. Galani C, Schneider H. Int J Public Health. 2007;52:348–359.
A guide to GRADE guidelines for the readers of JTH. Guyatt G, Eikelboom JW, Akl EA, et al. J Thromb Haemost. 2013;11:1603–1608.
Alternate day fasting for weight loss in normal weight and overweight subjects: a randomized controlled trial. Varady KA, Bhutani S, Klempel MC, et al. Nutr J. 2013;12:146.
Alternate day fasting and endurance exercise combine to reduce body weight and favorably alter plasma lipids in obese humans. Bhutani S, Klempel MC, Kroeger CM, Trepanowski JF, Varady KA. Obesity (Silver Spring) 2013