Intermittent fasting may be controversial, but it's no fad. It's revolutionizing the way we think about weight loss.
By John Romaniello
Intermittent fasting might be the most buzzed about dietary concept on the internet right now. Like many other breakout diets, intermittent fasting (IF) is growing by leaps and bounds. In contrast to most of the other diets, however, IF is gaining ground despite the fact that the practice challenges many long-held assumptions about nutrition.
In fact, practicing IF forces you to eat in direct opposition to those assumptions, and that -- along with the results -- is what's generating all the buzz.
Before we get into the why and the how, let's first discuss the basics of the what. What is Intermittent Fasting?
The most accurate definition is the simplest one: IF is merely the alternation of intervals of not eating (fasting) with times where you are allowed to eat.
Or, to use IF parlance, you alternate a fasting period with a feeding window. How long each will be varies depending on which type of IF programming you select -- and there are several to choose from.
Each method of intermittent fasting will be discussed in a later article, but for now it's enough to mention that the differences in programming come from expanding the fasting window. The fasting period on specific plans can range from 16 hours all the way up to 36 hours (with several stops in between), and each of those specific plans will have benefits.
It's also important to note that every one of us does some form of fasting -- whether you realize it or not. The least technical-while-still-being-accurate definition of fasting is simply "not eating," so anytime you're not eating, you're fasting.
Most of us aren't on a structured timetable of meals where the window of fasting is constant, so rather than fasting intermittently, we're fasting haphazardly -- and there's no benefit there.
The exception for most people is sleep. When you're sleeping, you're fasting; therefore, most of us have a fairly rigid fasting period of 6 to 8 hours per night until we eat in the morning. It is for this reason, by the way, that our morning meal is called "breakfast," as you are literally breaking your overnight fast. That brings us to our next point. Breakfast: The Most Important Meal of the Day?
Breakfast is sort of a hot topic in the IF world, and in fact, seems to be the first point of contention for people looking in on intermittent fasting from the outside. Don't we need breakfast?
Intermittent fasting proponents tend to say no -- which flys in the face of much of the dietary advice coming from every authority from registered dieticians to MDs.
For years, we've been told that breakfast is the most important meal of the day. In fact, many people are often scolded by their physicians for skipping breakfast, particularly people who are embarking on a plan to lose weight.
There is some credence here: A study conducted in 2008 showed that participants who ate a calorically dense breakfast lost more weight than those who didn't. The espoused theory for the results was that the higher caloric intake early in the day led people to snack less often and lowered caloric intake overall.
The value of that study has been questioned for many reasons, not the least of which is that despite the fact that roughly 90% of Americans eat breakfast, close to 50% of Americans are overweight. If eating breakfast is the first step to weight loss, then something else is going wrong.
More evidence seems to support the breakfast idea, though. There are some epidemiological studies that show a connection between skipping breakfast and higher body weight.
Of course, proponents of the breakfast theory are quick to suggest that most people are simply eating the wrong breakfast. Quick and easy meals like danishes and doughnuts can lead to weight gain.
However, the crux of the breakfast study is that, ultimately, a larger breakfast leads to lower overall caloric intake. That is, the argument for a larger breakfast boils down to energy balance. If weight loss comes down to "calories in" versus "calories out," then the composition of the food shouldn't matter. If we've learned anything from Mark Haub's Twinkie diet, it's that you can eat garbage and lose weight; clearly, something else is at work.
The only real argument that the breakfast crowd have is insulin sensitivity. In very basic terms, the more sensitive your body is to insulin, the more likely you are to lose fat and gain muscle. Increasing insulin sensitivity almost always leads to more efficient dieting.
Supporters of eating breakfast argue that since insulin sensitivity is higher in the morning, eating a carbohydrate-rich breakfast is going to have the greatest balance of taking in a large amount of energy without the danger of weight gain.
This brings us back to IF. You see, insulin sensitivity isn't higher in the morning; it's higher after the 8-to-10 hour fasting period that you experience when you sleep. More specifically, insulin sensitivity is higher when glycogen levels are depleted, and liver glycogen is somewhat depleted during your sleeping fast.
Intermittent fasting takes that a step further: It seems that extending the fasting period beyond that 8 to 10 hours by skipping breakfast (and, therefore, further depleting glycogen) will increase insulin even further.
Insulin sensitivity is also increased post exercise (due to further glycogen depletion in addition to other mechanisms), thus, in many cases IF proponents suggest compounding benefits by training in a fasted state and then having a carbohydrate-rich meal immediately following your workout.
Ultimately, this all means that there's nothing special about breakfast and that there's no need to eat first thing in the morning -- the first meal you eat to break your fast will be exposed to the benefits of increased insulin sensitivity.
A discussion that mentions skipping breakfast, or any meal, really, will invariably lead into a discussion of meal frequency, which leads us to our next point. The Myth of Six Meals
It seems that over the past 15 to 20 years, hundreds of diet books have been printed and no two are identical. In fact, many of them have been in direct opposition.
Calorie-restrictive plans like Weight Watchers certainly don't agree with plans like the Atkins diet, the first iteration of which allowed dieters to eat all they wanted as long as they kept carbs low.
Similarly, carb-conscious plans generally call for products like yogurt or cottage cheese to be used as portable sources of protein, but many plans to reject dairy products altogether.
Despite the incredibly disparate nature of so many of these diets, the one thing that has been consistently suggested in most books published over the past 20 years is the frequency of meals. If you've ever read a diet book, seen a nutritionist or hired a personal trainer you've probably been told that in order to lose weight, you need to eat five to six small meals per day (this suggestion is sometimes phrased as three meals and two snacks).
This style of eating, commonly referred to as the frequent feeding model, is popular with everyone from dietitians to bodybuilders and has been repeated so often for so long that it's generally taken as fact.
Which it isn't.
In fact, the reputed benefits of eating small meals more often have never been scientifically validated.
The first and most commonly cited of these is that eating frequently "stokes the metabolic fire." To put it less colloquially, the theory suggests that since eating increases your metabolic rate, the more often you eat the more your metabolic rate will be elevated. While that's true, it doesn't lead to more fat loss -- in fact, it's been scientifically proven that there won't be a difference at all.
When you eat, your metabolic rate increases because of the energy required to break down the food you've taken in. This is called the thermic effect of food, or TEF. So, while you're experiencing energy expenditure due to TEF every time you eat, the net effect is no different regardless of how many times you eat, as long as the total amount of food is the same.
TEF is directly proportional to caloric intake, and if caloric intake is the same, at the end of the day there will be no metabolic difference between eating five to six meals or two to three. In fact, as long as the total calories are the same you can eat 10 meals or one meal, and you'll still get the same metabolic effect.
Further, one study has shown that eating more frequently is less beneficial from the perspective of satiety, or feeling "full."
That means that the more often you eat, the more likely you are to be hungry -- leading to higher caloric intake and eventual weight gain.
Intermittent fasting guru Martin Berkhan has summarized this study, its meaning and the effects of such things quite well, but suffice it to say that it seems people who eat larger meals less frequently take in fewer calories and are more satisfied doing so.
A smaller number of meals obviously fits well into fasting protocols -- if you are condensing the amount of time you're allowed to eat into a small window of four to eight hours, having more than two to three meals becomes impractical at best and impossible at worst. My clients who practice IF eat three meals (not counting a post-workout shake, which they consume on days they train with weights).
Benefits of Intermittent Fasting
Obviously, above and beyond the debunking of long-believed myths, there are numerous benefits to intermittent fasting that make it so popular.
Firstly, as we've established thus far, people who practice IF eat less frequently. In addition to feeling hungry less often and more full when they do eat, these people benefit in terms of practicality and logistics.
After all, eating fewer meals means preparing or buying fewer meals. In addition to saving your time and money, this also means that you're exposed to flavors less often and, therefore, are less likely to get bored and eat something that you shouldn't.
We've also mentioned that eating less frequently tends to result in eating fewer calories overall, but that's a pretty important point so it bears repeating: Eating less frequently tends to result in eating few calories overall.
And speaking of caloric restrictions, that brings us to another benefit. Intermittent fasting plans that require full-day fasting drastically reduce your calorie intake. If you are using a style of IF that requires you to fast for 24 hours twice per week, you're reducing your food intake by about 30%. It's not hard to see how that would lead to weight loss.
If that isn't incredible enough, keep in mind that caloric restriction has been linked to things from increased longevity to decreased risk of disease to heart health. In fact, one study out of the University of Utah showed that people who fasted just one day per month were 40% less likely to suffer from clogged arteries.
While there's certainly a lot to be said for caloric restriction, it's important to keep in mind that intermittent fasting isn't just about eating fewer calories -- there are also hormonal benefits that lead to improved body composition.
As we've already mentioned, there's the improved insulin sensitivity that comes with fasting, especially when paired with exercise. Additionally, fasting has other hormonal benefits including (but not limited to) an increase in the secretion of growth hormone (GH).
Growth hormone has a myriad of benefits (a discussion of which in full is beyond the scope of this writing), but for our purposes it's enough to say that the more GH your produce, the faster you can lose fat and gain muscle. Additionally, GH tends to offset the effects of cortisol, which is (in part) related to belly fat storage. So, it seems likely that fasting can help you lose belly fat, at least indirectly.
Still not satisfied? If you need another benefit, fasting reduces inflammation as well, which can have implications for improved immunity as well as increased fat loss. Wrapping Up
The most important thing to remember about Intermittent fasting is that it isn't a diet, it's a way of eating -- a nutritional lifestyle -- that will allow you to reach your goals in an efficient and convenient manner and then hold onto your physique once you achieve your desired weight.
While IF isn't for everyone, nor is it a perfect system, it's certainly an effective way to lose weight.
In addition to the hormonal benefits inherent in the practice, you'll also feel more satisfied from your food, feel hungry less often and probably save some money on meals.
Moreover, you may also live longer if, you know, you're into that.
Even if you never try IF you can at least appreciate that it's forced the industry at large to reevaluate the "truths" we tend to cling to.
Perhaps it's for this reason that intermittent fasting is being generally received with appreciation and acceptance while low-carb diets, Paleo eating and the "Twinkie diet" all have people on both sides of the line either praising or lambasting them. Intermittent fasting is well received once people see the research, and there's a simple reason: it works.
Next time, we'll discuss the various methods of intermittent fasting, touching on the theories and reasoning behind each protocol, as well as the fitness professionals popularizing each plan.