So what exactly is intermittent fasting? Intermittent fasting in its most basic terms is a diet approach that incorporates extended periods of fasting (not consuming calories) followed by a period of time restricted feeding. There of course are many other details and variables and don’t worry, I’ll get into them.
When you look at the research, many of the current literature evaluates one of two types of intermittent fasting. The first being a style called “Alternate Day Fasting.” When researchers use alternate day fasting protocols, it usually involves placing individuals on a protocol where one day they consume roughly 25% of daily caloric needs, followed by a day of ad libitum (non restricted feeding). Some protocols however use the fasting day as a day of complete abstinence from food. I’ll get into the details of that and why it may not be an optimal path to go down, a little later.
The second primary type of intermittent fasting used in research is the type of fasting that is associated with Ramadan. Ramadan is a spiritual Muslim practice in which individuals fast from sunrise to sunset. Upon sunset, many practitioners feed throughout the night and rise early to consume food prior to sunrise. In essence, these individuals practice intermittent periods of fasting throughout the month of Ramadan.
Apart from that of which is involved in research, there are other forms of intermittent fasting that those in the physique world use. The warrior diet is a form in which individuals typically fast for a period of 20 hours, followed by a feeding period of 4. Last but certainly not least, is the LeanGains style of intermittent fasting, brought forth by Martin Berkhan which incorporates a fasting period of 16 hours followed by a period of 8 hours of feeding.
In later posts, I’ll discuss some of the current evidence on the predominantly researched forms of intermittent fasting and then extrapolate from those papers as wells as others to determine which route is ideal for “athletic” individuals looking to optimize body composition. However, for the purpose of this article, I’d like to simply give an overview of possible mechanisms that give credence to the idea of intermittent fasting.
What are some reasons that intermittent fasting may be effective?
The first and likely most apparent mechanism is that when individuals restrict the amount of time that they have access to food, they simply eat less. A majority of regular people eat constantly throughout the day and typically that amount of food goes un checked. Just by skipping a meal, there is a likely chance that these individuals are missing out on a significant portion of calories. This leads to the idea of energy balance. It is postulated that weight loss is attributed to this idea of expending more calories throughout the day than you consume. This is typically caused by the following: reducing calorie intake, increasing activity levels or a combination of both.
Second, intermittent fasting may allow for reductions in fasting insulin levels and subsequently increases in insulin sensitivity (3). This is hypothetically even more important for overweight and obese individuals. As a refresher, insulin is secreted in response to rising blood glucose concentrations (ingested carbs = increased glucose in the blood). When insulin rises, it causes the glucose to be disposed in body tissues for storage. This a good thing. However, chronically elevated insulin levels is not. Having insulin constantly elevated does a few things that we want to avoid. First, having constantly elevated insulin levels can lead to insulin resistance, meaning that more and more insulin needs to be secreted in response to the same amount of glucose. Eventually, you can reach a point in which the insulin can’t keep up with glucose and you develop Type 2 Diabetes; something I’m guessing you want to avoid. Further, insulin can inhibit lipolysis. Lipolysis is the freeing of fat from adipose tissue into circulation. This is necessary to oxidize or “burn” fat. When individuals intermittent fast, we see 1. a reduction in insulin during the fasting period, 2. an increase in lipolysis and free fatty acids in the blood, 3. an increase in fat oxidation (burning) and 4. an increase in insulin sensitivity.
Third, research indicates that individuals that intermittent fast may be able to retain lean muscle mass better than their simple caloric deficit counterparts, which is contrary to popular belief. Again, a topic of which I’ll get into at a later time.
anticipation of the meals. It thus stands to reason that if an individual fasts regularly, these circadian rhythm genes are not expressed, in turn attenuating the secretion ghrelin. Ipso facto, you don’t get hungry during the fasting period. Pretty incredible to say the least.
The above paragraphs indicate some of the possible reasons that intermittent fasting may be beneficial. Arguably the most important detail is that IF may result in reductions in energy intake. This is likely the primary reason that individuals see reductions in weight (which can include fat mass). If you are not in a caloric deficit or rather a negative energy balance, there is a high probability that you will not see reductions in weight. Some research indicates that fasting may increase the likelihood that weight reductions are attributed to reductions in fat mass while sparing lean muscle tissue. Some other research indicates that fasting may result in elevations of catecholamines which may increase the rate of lipolysis further than that of simply restricting calories. Further, the same catecholamines may specifically help target stubborn fat areas. These are things that I’ll get in later posts.
Just remember that Intermittent Fasting is simply a tool. It is not one size fits all. You don’t need to do it, but I would suggest giving it a second thought. If you are considering intermittent fasting, it is suggested that you start with a fairly short duration of fasting. A good starting point is to simply continue fasting for 2 hours after you wake up. As you get accustomed to this, periodically extend the period of fasting until you hit (what I suggest) 16 hours. Finally, if you decide to try this out, make sure that you give it a couple weeks before abandoning it. The biggest reason people quit is because they are hungry. You’ve spent an entire lifetime eating breakfast. As I described earlier, you’ve been expressing circadian rhythm genes associated with ghrelin, at those times for a very long time. It stands to reason that it may take more than a day or two to reset itself. Consciously assess the situation and learn to distinguish between biological hunger (ghrelin, circadian gene expression) and mental hunger (I just think I’m supposed to be hungry). Remember that the most effective diet is one that you can stick to. If you’re anything like me, you may end up considering this to be a lifestyle change rather than a diet approach.
Stay tuned for some future posts regarding intermittent fasting. Lots of exciting stuff to come in the future. Please feel free to ask any and all questions. If I think your question is worthy, I will even feature it in an extended blog format answer.