When it comes to fads, diets go hand in hand. While that doesn’t mean they don’t necessarily work, it’s easy to get caught up in the paleos, the ketos, the Atkins, the vegans, or the Mediterraneans. What food should you really be eating, at this point?
Another diet that has become extremely popular in recent years has been intermittent fasting. But rather than being about what you should or shouldn’t be eating, the question becomes when you should or shouldn’t be eating.
This unique take on dieting allows for a lot of flexibility when it comes to the foods you eat. And although the point is to restrict your eating time, intermittent fasting also allows for a lot of options in terms of when exactly you eat. This diet is popular for a reason, and a lot of people have experienced success following it. If you’re looking to lose some weight and reap some extra benefits, this might just be the eating routine for you.
Whether or not you know about it, everyone does some form of intermittent fasting. The most common is from when you go to sleep to when you wake up for breakfast. And if you’re getting blood work done that morning, chances are your fast will last even longer. That is, until you’re able to “break the fast” with, you guessed it, breakfast.
With intermittent fasting, the point is to be intentional with the whole thing, rather than it happening by chance. But because everyone already fasts during their sleep, a lot of the work is already done for you, in a sense. This diet plan helps people make the most of this natural cycle and allows for eating windows and fasting windows that naturally restrict the amount one consumes.
And what do we get when we restrict the amount we eat? Weight loss.
But long before intermittent fasting the diet it is today, fasting has been a part of human culture for thousands of years.
Part of this comes down to the simple fact that food was a much scarcer resource before agriculture came around. There wasn’t any farming of food, let alone storing it, so our ancestors likely had to wait significant periods between meals. While the need for this type of fasting has gone away in large parts of the world, it’s also continued in various cultural forms.
For example, fasting and moderation are parts of Ash Wednesday and Good Friday for Christians, while Muslims don’t eat from sun-up to sun-down during the time of Ramadan. Some Buddhists take it a step further and incorporate fasting into their daily lives and practice, helping them to clarify their minds.
It’s obvious that fasting has been part of our cultural and social makeup for a very long time, with its benefits touted by a variety of people over time. But do these claims have any basis in the modern era?
Let’s take a closer look.
Intermittent fasting, like many other diets, is all about trying to lose weight.
And it makes a lot of sense—if you limit the amount of time you have each day to eat, it’s going to likely lead to you eating less and therefore consuming fewer calories. Keto being the most obvious exception, pretty much every diet relies on “calories in-calories out,” meaning that in order to lose weight, you need to be consuming fewer calories than you burn.
Seeing as how a pound of body fat is about 3500 calories, it makes it easier to conceptualize a progressive weight loss routine. For example, one intermittent fasting routine has you fasting for two days each week. Although difficult, it automatically cuts out about 30% of the calories one eats through the week.
There is also some evidence that suggests that intermittent fasting can change the hormone levels that facilitate greater weight loss. This is the fat-burning hormone norepinephrine, and it’s compounded by the lowering of insulin and increasing growth hormone levels—all good things for weight loss and overall health.
In fact, most studies on intermittent fasting have shown that the process is beneficial to an extent when it comes to fat loss. These losses usually range from 2.5% to 9.9%, most likely due to both the natural calorie restriction of the diet, and its effects on hormones.
Other than the weight loss benefits, intermittent fasting has a host of other benefits. However, it should be kept in mind that these aren’t all proven beyond a doubt.
One benefit is an improvement in insulin sensitivity. A study found that intermittent fasting was able to lower blood sugar levels by 3% to 6%, while also lowering insulin levels during fasting by 20% to 31%. Other studies have also shown significant benefits for diabetics who switched over to an intermittent fasting schedule, seeing benefits in body fat, glucose, and its variability after meals.
Even for those with prediabetes, intermittent fasting has been shown to cause improvements. Namely, these improvements were in blood pressure levels. However, there is also evidence that suggests that fasting can lower bad cholesterol levels, act as an anti-inflammatory, lower blood sugar, insulin resistance, and blood triglycerides. All of these factors are markers of heart disease, and so it seems that intermittent fasting may be good for the heart as well.
Your gut health may also potentially benefit from intermittent fasting. While the evidence for this is a bit more tenuous, some studies have suggested that fasting is able to change the microbiota of the gut in positive ways, leading to decreased chances of obesity and the browning of white adipose tissue.
Sleep habits may also benefit from intermittent fasting since there’s a close link between fasting and one’s circadian rhythm which controls sleep and wake schedules. During these periods of fasting, your body undergoes repair through various mechanisms, which may go as far as to suggest links to a longer life.
This last claim is probably the least known about, but it’s worth mentioning. Although studies have mainly looked at animals in this case, several biomarkers of lifespan have been noted in animal subjects that have been put on intermittent fasting schedules.
These biomarkers include an increase of the resting metabolic rate, lowered insulin levels, and reduced core temperatures. Our bodies may also become more resistant to oxidative stress, with fasting acting as a sort of anti-inflammatory. All of these factors have been linked to healthier immune systems and longer lives.
Some people also report feelings of heightened mental clarity and improvements when it comes to concentrating and energy levels. However, no solid evidence for these aspects exists as of yet.
While fasting is likely to be as old as the human experience itself, that doesn’t mean there aren’t any drawbacks to this eating schedule.
While most people in good health will be fine, some side effects of intermittent fasting may include feelings of extreme hunger, stress, tensions, confusion, anger, mood swings, lower energy levels, and overeating during the feeding windows.
These are more likely to be reported by those with lower body weights, and also in the first few weeks of fasting. As with most things, your body can adapt to a wide variety of more extreme schedules, and so it might take a while to get used to fasting.
However, if these feelings persist and you’re getting unwanted side effects for a prolonged period of time, it’s best to seek help from a healthcare professional or simply avoid fasting altogether.
Generally, most people will be fine if they’re in good health. However, there are some groups of people that may want to avoid fasting altogether—or at least be more aware of the risks.
There have been reports of women that began intermittent fasting practices and whose menstrual periods stopped. For this reason, it may be helpful for women to be more careful with intermittent fasting, or at least not do the more extreme variations of it.
Other groups which should avoid intermittent fasting are those with eating disorders, or those recovering from eating disorders.
Because this diet emphasizes longer periods of caloric restrictions, it can be quite easy to binge eat during the eating window. Since this activity is associated with eating disorders, it may be better to focus on eating nutrient-rich and whole foods instead.
People who are recovering from injuries or under extreme stress may also want to avoid intermittent fasting. If you find yourself in this group of people, it’s more important to nourish your body and focus on eating enough protein and whole foods, rather than restricting your diet in such a way.
This mostly covers every group that has additional energy needs. This also includes pregnant and breastfeeding women who need enough calories to maintain the correct bodily processes. Other populations that should avoid intermittent fasting, include:
Our bodies are unique and complex, so every individual will be affected slightly differently by intermittent fasting. It’s one of those things that may not be for everyone, and so even if you don’t fall into one of the categories above it may be good to reconsider fasting if you experience persistent side effects.
One of the benefits of intermittent fasting is in the variety of methods that exist. They range from modest enough that you may be doing them already without realizing, to relatively extreme cadences that have you fast for over a day. The hours of fasting and days of the week are also up to you.
It’s always best to begin with the modest approach to see if it’s something that works for you. If you’re seeing benefits and not experiencing side effects, then you can slowly work your way up to where you’re comfortable.
The 12/12 Fast
This is a time-restricted eating method which also happens to be the most modest pattern.
If you don’t already eat late at night, then chances are you might already be close to doing a 12/12 fast. As the name suggests, your feeding window is 12 hours and the fasting window is 12 hours. So, if you’ve got your last meal at 7 pm, breakfast should be at 7 am.
It’s easy to remember, and easy to incorporate around a regular sleeping schedule. This pattern is great at cutting out late-night snacking, which is where most people go wrong when trying to lose some weight. Eating closer to bedtime can also interfere with your sleeping schedule, so limiting your last meal to an earlier time can have cascading positive health effects.
A more advanced version is the 14/10 fast, which usually means that you’ll have to push back breakfast a few hours while either maintaining the time of your last meal or bringing it forward.
The 16/8 Fast
This is the form of intermittent fasting that’s the most popular. It’s much more extreme than the relatively modest 12/12 method, but it’ll also impart greater benefits if done correctly. This is sometimes called the “Leangains protocol”.
Although not eating 16 hours of the day sounds difficult, it’s important to keep in mind that about 8 of those hours you’ll be sleeping instead. If you consider eating breakfast at 8 am, lunch at noon, and dinner at 4 pm, the idea of 16/8 becomes a whole lot more manageable.
You’re also welcome to do this with two meals: eating a large breakfast and a large dinner.
As you might’ve guessed, the full-day fast is the one where you don’t eat for a 24-hour period.
These can be done as frequently as you’d like, up to twice a week. Or feel free to do it just once a month—as long as it works with your lifestyle and goals. Although rare one-day fasts may not sound like they’ll benefit you the most, the greatest shift from glucose to fat as a primary energy source happens after 18 hours. Furthermore, some research suggests that occasional full-day fasts can improve cardiovascular health as well.
One of the cadences that one can practice with the full-day fast is the 5:2 fast, which involves two days during the week where you don’t eat. These days aren’t meant to be consecutive, and the other 5 days are allowed with any type of eating schedule. This offers flexibility for more people since the two fasting days can be any two in the week.
It’s also important to keep in mind that you don’t completely eliminate food during the fasting days. Rather, you should stick to about 20% to 25% of your energy needs for the day or about 500 calories for women and 600 calories for men.
Another popular full-day fast is the alternate-day fasting method. Each eating day is followed by a fasting day. And much like the 5:2 method, the fasting days limit food intake to about 20% to 25% of daily energy needs. This is a good method for faster weight loss and introducing some consistency into your routine. However, it’s significantly harder than some of the other fasts we’ve looked at.
While waiting to eat for greater weight loss seems like an easy formula to follow, there are several things to remember. The first thing to consider is what you can actually ingest during fasting times.
“Nothing,” is the obvious answer, but you’re able to drink water, tea, coffee, and other drinks that don’t include calories. Certain teas are especially useful for weight loss, and coffee and tea can help to keep you satiated for longer. Sugar, milk, or cream are obviously off the table, however.
What about when you’re in the feeding window?
While intermittent fasting doesn’t emphasize any particular foods or diets, that doesn’t mean you can (or should) go wild with what you consume. Especially if your goal is weight loss, intermittent fasting won’t be very conducive for your aims if your eating window contains a lot of processed and unhealthy foods. The name of the game is fewer calories, but the type of caloric intake also matters.
That’s why you should stick with nutritious, whole foods that aren’t just better for you, but they’ll also keep you fuller for longer. This means healthy fats, healthy carbohydrates, and lean protein.
To begin with intermittent fasting, first, make sure you’ve got access to healthy foods. Then, consider what your sleeping schedule is like and then mold the fasting period around that. It’s easiest to start with a 12/12 fast since it pretty much just cuts out evening and late-night snacking. From there, you can restrict your eating schedule further.
Keep in mind that it will take some time for your body to adjust to the new eating schedule and the restrictions. But don’t throw in the towel—keep your eyes on the prize and you’ll be reaching your goals before you know it.