What is Intermittent Fasting?
Although intermittent fasting has been around for many years, this phenomenon has recently gained a significant amount of attention. Intermittent fasting has a few variations that are simply cycles of eating and fasting. Celebrities such as Ben Affleck, Beyonce, Terry Crews and many others swear by this eating lifestyle. Intermittent fasting is an eating pattern, not a diet. I don't consider it to be a diet because it has little to do with what you eat and more to do with when you're eating.
What types of Intermittent fasting are There?
The 12-16 Hour Fast
The most common variation of intermittent fasting that I encounter is fasting for 12-16 hours each day. Sounds crazy right? Some people will do this fasting overnight into the afternoon to make it a bit easier. For example, having your last meal of the day at 8:00 pm and fasting until 12:00 pm the next day would be a successful 16 hour fast. That gives you 8 hours of the day to get all your nutrients in.
Alternate Day Fasting
This method consists of fasting every other day. You're generally allowed to eat however you please for the first day and fast the following day. That can be very difficult for someone who is just getting introduced to this eating pattern. Some will practice this method by eating just 20-25% of their daily calories on the fasted day instead of completely fasting. Others will restrict their calories to 500-600 calories a day on their fasting day.
The 5:2 Method
This style of intermittent fasting is a bit easier to practice than alternate day fasting. The 5:2 method allows you to eat normal for 5 days a week and drop your calories to 500-600 on those two fasted days of the week (5 unrestricted days, 2 fasted days).
Where's the facts? Although there are many studies indicating the health benefits of intermittent fasting, they have been mostly conducted on animals. A study conducted by Louisiana State University Medical Center, involved monitoring 10 adults with moderate asthma and a BMI >30 for 8 weeks while they practiced alternate day fasting (Free Radical Bio Med 2007;42:665–74). They alternated between normal eating days and days of <20% of their normal calorie intake on intervening days. 9 out of 10 participants who adhered to the "diet" lost 8% of their initial body weight. Within two weeks they also experienced an improvement in asthma related symptoms and quality of life. Mark Mattson, senior investigator for the National Institute on Aging, took part in this study. He believes that fasting has shown to reduce oxidative stress, preserve memory/learning function and also improve biomarkers of disease. The methodology of this hypothesis is that cells are under a mild stress during the fasted stage. "They respond to the stress adaptively by enhancing their ability to cope with stress and, maybe, to resist disease," according to Mattson. When someone is in a fasted state for 10-16 hours, fatty acids called ketones are released into the body. When the body begins to use fat stores as energy, it has been known to slow down the processes of disease to the brain.
Am I Going to Lose Muscle Mass? A study consisting of 34 men with at least 5 years of resistance training experience was conducted to understand the effects of intermittent fasting on maximum strength and body composition. Participants were randomly selected to perform either time restricted feeding or perform normal feeding patterns for 8 weeks. The workouts and diet were controlled. The time restricted participants were to eat all of their meals within an 8 hour period (meals at 1:00pm, 4:00pm, 8:00pm), while the normal diet group had their 3 meals at 8:00am, 1:00pm and 8:00 pm. The study concluded with both groups maintaining strength and fat-free mass, while sustaining no muscle loss (around the arm and thigh). The group that was intermittent fasting lost about 3.5 pounds of fat (not 3.5 pounds total, 3.5 pounds of strictly fat), whereas the normal dieting group didn't lose significant amounts of fat during the 8 week study.
My Opinion
I did intermittent fasting for about 7 weeks while monitoring my macronutrient intake on a daily basis. I was on a high protein diet, exercising 5 days a week and doing 20-25 minutes of cardio 3 days a week. Every day I would ingest roughly 1 gram of protein for every pound of lean muscle that I had. Since I was 180 pounds I was eating about 165 grams of protein a day (assuming 165 of my 180 pound body was lean muscle). At first, I was losing weight (which was my intention) while maintaining strength levels, if not increasing in certain areas. 8:00-9:00pm was when I would cut myself off from food for the night. At first, it was very difficult for me to eat all of my food within only 8 hours of the day. This is when my emotional eating habits became apparent to me. I must have developed this habit throughout college and never paid much attention to it. My late night cravings to eat that have always been an issue for me began to disappear after a week of fasting. I was losing weight, maintaining strength and beginning to like what I saw in the mirror again. My goal was to keep dropping the calories and upping the work output. My energy levels began to become noticeably lower. However, I blame my caloric deficit for my lower levels of energy more than I blame intermittent fasting. Nobody says you have to count your calories in order to intermittent fast, but I do recommend it since the general idea of this eating pattern is to eat less. This could be an ideal style of eating for the person who is trying to lose a significant amount of fat. Say you go to bed at 10:00 pm and don't eat again until 10 am the next morning. You're already 12 hours fasted and could work your way up to longer periods. The word fasting seems a little frightening at first and it was frightening the first week like I mentioned, but this eating pattern became easy after that grace period of adjusting. Could you get the same results from just counting your macronutrients and working toward slowly decreasing your calories? Sure you can, and maybe thats the only change you really need to make to your diet. Like I said, this eating pattern COULD be a useful method for someone trying to lose a significant amount of fat.