Intermittent Fasting: Feast AND Famine?

“Drink this expensive protein shake, and you’ll drop 3 sizes in 10 days!” “Take these pills, and in just 1 month you’ll lose 50 pounds; no exercise required!” Juicing cleanse. Water fasting… The dreaded “boiled egg diet.” We are constantly bombarded with new products, diets, and promises of better health, more energy, and longevity. How can we possibly navigate through the media and determine which claims are worth a try, and which ones are total bunk? Well, the first rule I always remind myself of is if it sounds too good to be true, then it probably is. That can knock out quite a few fads right off the bat. But what about the ones that sound like they may actually have some truth behind them? One diet in particular that seems to be peaking everyone’s interest is “intermittent fasting,” but why? Let’s take a closer look.

             Intermittent fasting (IF) has been around for centuries as a part of certain religious practices, but it has recently been gaining popularity in the media as a potential weight-management solution. IF is any diet that incorporates a period of voluntary caloric restriction; i.e. purposely avoiding food or beverage (other than water) for a given amount of time as a way of controlling caloric intake. The most commonly studied types of IF are as follows:

•        Alternate-day fasting – eating regularly some days, but alternating with days where zero calories are consumed.
•        Modified fasting – rather than consuming zero calories on fasting days, calories are restricted to 20-25% of an individual’s needs. These fasting days are still alternated with “regular” or unrestricted days of eating.
•        Time-restricted feeding – each day contains a fasting period where zero calories can be consumed. The remaining “window” allows for unrestricted caloric intake. The most common type of time-restricted feeding is to incorporate an extended fast overnight.

So, how does it work? That hasn’t been completely figured out yet, but there are some viable theories. Essentially, it is believed that people become predisposed to obesity and associated diseases such as diabetes and cardiovascular disease when their lifestyle behaviors, sleep patterns, and gut microbiota (healthy, naturally occurring microorganisms) are out of balance. Current advocates of IF suggest that by practicing IF, an individual can reset these imbalanced issues. This results in decreased insulin, less inflammation, weight loss, and ultimately lower risk of diabetes, cardiovascular disease, and even cancer. For some individuals, a certain type of IF may not be far from what their current eating schedule is like, so it may seem like a sustainable, long-term possibility. That may not be true for everyone though. As with any diet, there is not a one-size-fits-all solution. In fact, it could even be dangerous for some.

IF is a restrictive eating pattern and should not be attempted by anyone that either has or is at risk of developing an eating disorder (anorexia, bulimia, binge eating disorder, avoidant/restrictive food intake disorder, or other specified feeding and eating disorders). It can trigger old habits or cause someone with no former eating disorder diagnosis to suddenly develop inappropriate and unhealthy eating behaviors. IF may also be unsafe for individuals with diabetes as they have not been studied specifically. Diabetes causes irregularities with insulin levels, and since it has been suggested that IF reduces insulin, it could potentially cause someone with diabetes to develop dangerously low blood sugar levels.

In general, it appears IF may have some health benefits, but more human studies need to be conducted before that can be officially proven. The studies that have been conducted seem promising but have either contained a small number of participants, lacked controls, or had mixed results. Actually, IF may not be any better than a typical calorie restricted diet when it comes to short-term weight management. Also, many claims are based on findings from rat studies which we can’t just assume translate to human subjects. Only time will tell. Whatever you choose, play it safe, and consult your healthcare professional before making any changes to your diet or exercise routine.

Callie Shaw is a Dietetic Intern in the combined Dietetic Internship and FCS Master’s degree program at NMSU with a B.S. in Nutrition/Dietetics from Indiana University of Pennsylvania. She believes that knowledge is power, and she is dedicated to sharing nutrition education in community settings to improve public health throughout the region. 

References available upon request.