You’ve heard the classic idea that skipping meals is bad for health, haven’t you? We’re often told that missing a meal or two promotes an unhealthy relationship with food and means that we’ll just eat more at the next meal. Intermittent fasting suggests something completely different. So, is intermittent fasting good for you or is it just another weight loss fad?
As the name suggests, intermittent fasting means that you’re cycling between eating periods and fasting ones. The schedule depends on the intermittent fasting method you choose and each method has its own advantages.
Unlike regular fasting, intermittent fasting isn’t normally a religious or a cultural practice. Instead, it’s often used as a weight to improve your health, get your eating on track, and even lose weight.
The approach does have clear advantages. But, as you’ll see, there are some risks too.
Fasting isn’t the entire story either. You also need to make wise decisions about the food you eat. Many intermittent fasters focus on whole food eating approaches, like the Mediterranean diet or even veganism. The practice is also common among keto dieters.
Is Intermittent Fasting Good For Your Health?
- Intermittent Fasting Approaches
- The Benefits Of Intermittent Fasting
- The Risks Of Intermittent Fasting
- What Can You Eat?
- How Strict Do You Need To Be?
- Who Shouldn't Fast?
- Final Thoughts
Intermittent Fasting Approaches
Intermittent fasting involves alternating between eating periods and fasting periods. The pattern of these periods varies depending on the approach that you take.
People also vary in how strictly they follow their schedule. Some follow it rigidly, while others flex their eating and fasting based on other aspects of their life. To begin with, we’re going to look at the different schedules. Later on, we’ll talk about how strict you need to be when fasting.
Fast In A Daily Window
The simplest approach to intermittent fasting involves having a fasting window and an eating window each day. Most people keep to a schedule, so that their fasting window is always at the same time each day, making it easy to get into a rhythm with the technique.
The most popular version is known as 16:8 or 16/8 intermittent fasting. This involves fasting for 16 hours and only eating in an 8-hour window. A 16-hour fast isn’t as difficult as it sounds, because those 16 hours include all the time that you’re asleep.
You can start simply by skipping a meal. Many people skip breakfast. This can be an easy approach if you find that you function well without breakfast (and many people do). Or, if your breakfast feels essential, you could have a breakfast, a large late lunch and then skip dinner instead.
There are other variations too, like 18:6, where you extend the fasting window by 2 hours. Doing so isn’t too difficult if you’ve been following a 16:8 schedule for a while.
With a 24-hour fast, you need to go a full 24 hours without eating at all. This can seem very difficult at first but does get easier over time.
This approach gives you flexibility, as you can choose how often you fast. You might start off simply, perhaps by fasting once every week or two, then increase the frequency as you get more confident.
You can also choose the time frame for your fast. So, rather than fasting an entire day, you might choose to start at 6pm, straight after dinner. You could then fast until 6pm the next day and have a late dinner. This way you’re fasting the full 24 hours, but you still have something to eat every day.
Alternate Day Fasting
Alternate day fasting is mostly what the name suggests – you eat and fast on alternate days. There are two main approaches here.
The first is to literally fast on the fasting days, where you’re not consuming any calories at all. In other words, you’re doing a 24-hour fast every second day. This can be tough, especially as some of those days will fall during the work week, where you need to remain functional.
Still, some people do follow this approach and live normal lives, as the fasting will get easier over time.
The second approach is to mimic fasting by having tiny meals on your fasting days (often around 500 calories or so). Ideally, you should also make sure that these are low carb meals, but that isn’t a strict rule.
Having small meals like this is much easier than a full fast. You should get many of the same benefits, as your energy intake is low. However, you won’t be entering a full fasting state, so this method might not be as powerful.
The 5:2 approach means that you’re fasting twice per week and eating regularly the other 5 days. Once again, you can choose whether you want to completely avoid food during the fast days or focus on tiny meals instead.
This approach is easier than alternate day fasting, as you only need to cut down food for 2 days each week. You could even change your fasting days from one week to the next based on your social calendar or your mood.
Which Is Best?
Alternate day fasting or 5:2 fasting may offer the most benefits, as you are fasting for 24 hours at a time. However, fasting for 24 hours isn’t easy, even once you get used to it. The approach can be frustrating too, as events may fall on days where you plan to fast.
Daily fasts are more realistic for most people. They’re not too difficult to sustain and you can switch the timing around based on your life.
If you skip breakfast, there isn’t much social impact anyway, as breakfast is often a meal that you eat on your own.
The sustainable nature of daily fasting is powerful. After all, a diet isn’t going to help you at all if you can’t stick to it.
The Benefits Of Intermittent Fasting
While fasting for health might sound odd, the idea has historical precedent. Think about human history for a moment. These days we have food on hand whenever we want it and we don’t tend to stay hungry for very long, if we can help it.
Earlier in history, humans would have gone through periods of satisfaction and scarcity. Our bodies would have adapted to this way of living, giving us the ability to function well and remain cognitively sharp, even when we were hungry.
Advocates for intermittent fasting argue that our bodies aren’t adapted to be in a constant fed state. Instead, some periods of hunger aren’t only good for us, they’re essential for functioning well and offer distinct benefits.
It Changes How Your Body Responds
Fasting periods influence your body in surprising ways. There can be changes in your hormone levels, gene expression, insulin levels, and processes of cellular repair.
These shifts can partly happen because your body isn’t always digesting food, so it can use resources elsewhere instead. At the same time, your body is readying itself to use fat as an energy source.
The changes in your body come with a surprising host of benefits. When done well, intermittent fasting might improve your immune system, rebalance your hormones, improve gut health, decrease inflammation, and increase your body’s ability to burn fat.
Some people have seen enormous benefits from intermittent fasting, finding that their health has improved in many different ways.
It Can Help With Weight Loss
While weight loss can be complex, there’s one general rule of thumb – you need to burn more calories than you consume. With intermittent fasting, you’re either skipping meals or eating very small ones, so it’s easy to cut down your calorie intake.
Some people find the approach much more achievable than trying to count calories, cut down carbs, or follow a strict diet plan. The style feels less restrictive too, as you can basically eat whatever you want during eating windows (which is why these are sometimes called feast periods).
Behavioral changes aren’t the only reason that intermittent fasting might help with weight loss. Another is that when you eat regularly, your body uses the energy from food to fuel you. When you fast, the body is forced to use your stores of fat as a source of energy, which then promotes weight loss.
We get this effect a little in the fasting period between dinner and breakfast. Intermittent fasting extends the fasting window, which could lead to more weight loss.
These weight loss benefits have been consistently seen with intermittent fasting studies. While the amount of weight loss isn’t that different than other techniques, the research shows that intermittent fasting truly can be effective.
May Improve Health
The weight loss effects of intermittent fasting can promote your health in a variety of ways. This effect alone could reduce the risk of diseases like diabetes and even cancer, along with problems like sleep apnea.
Intermittent fasting may also help with chronic inflammation, influencing your risk of inflammation-related conditions, like asthma, arthritis, and stroke.
There are other potential effects too, including the chance to help with neurological disorders, heart disease risk, and diabetes. Intermittent fasting could even extend your life, although research outcomes for that topic have been mixed.
It’s A Flexible Approach
Intermittent fasting is more flexible than many other eating approaches, like paleo, keto, calorie counting, or Weight Watchers. You get to choose which fasting schedule you follow and the foods you eat.
You can even switch your eating and fasting hours based on what works with your schedule and your needs. This flexibility makes intermittent fasting easier than many other weight loss approaches.
Plus, intermittent fasting doesn’t need to be all or nothing. While some people follow their fasting schedules strictly, others make adjustments based on their physical needs, what’s going on in their lives, and even their mood.
After all, even just doing a 16:8 fast a few days each week offers more benefits than not fasting at all. You can always increase your frequency of fasting as you go.
This flexibility is powerful, as it can make intermittent fasting a sustainable eating pattern. This is what you want – as strict diets rarely work in the long term because sooner or later you feel too constrained and stop. An idea like intermittent fasting, on the other hand, can be adapted and changed to fit in with your life, so it's much more realistic in the long term.
It May Help With Type 2 Diabetes
The link between fasting and diabetes is interesting. On one hand, fasting can make your symptoms worse and may even be risky. But, some people have found the reverse, that intermittent fasting helped them to get their symptoms under control.
Daily fasting, perhaps following a 16:8 schedule, could be the best approach here, as you don’t need to do long fasts.
However, anyone fasting with type 2 diabetes should consult with their doctor first. Diabetes is a highly individualistic condition and what works well for one person mightn’t do so for another.
Your doctor can also show you what to watch out for and help make sure that you stay healthy during your fasting.
The Risks Of Intermittent Fasting
There Are Side Effects
Intermittent fasting means that you’re ignoring your body’s signals about when you should be eating and sticking to a schedule instead. Not surprisingly, that process can lead to side effects, like mood swings, blood sugar changes, and headaches.
Some people also find that they have less energy and struggle to think clearly. This might be a serious problem if you still need to be functional while you’re fasting.
These side effects can be more extreme too.
For example, prolonged fasting and poor nutrition between fasts can lead to hypoglycemia, where blood sugars are extremely low. Shakiness, anxiety, and fatigue are all symptoms. This isn’t a good physical state for anyone to be in and is particularly dangerous for people with diabetes.
Thankfully, some of these side effects decrease with time. Your body often adjusts, and everything gets easier. Some people even find that the fasting windows are easy once they’ve fasted for long enough.
Still, we’re all different.
While many people function well once they’ve adapted to intermittent fasting – others never do. If you’re in this second group and are still experiencing low energy, brain fog, and frustration, then intermittent fasting mightn’t be the right choice.
It Might Lead To Weight Gain
If intermittent fasting is done poorly, it can end up promoting weight gain rather than weight loss. Part of the problem is that skipping a meal (or multiple meals) makes you hungry. Some people really struggle to get through the fasting window, fighting their hunger every step of the way.
When you’re this hungry, it’s easy to have far too much food once you get into your eating window.
This is made worse by the way that satiety signals are delayed. It takes time for our bodies to tell us that we’re full. If you eat fast because you’re hungry, then it’s easy to eat past what your body needs, as you don’t get the signal to stop soon enough.
Plus, if you’re only focused on when you eat, you could overdo it with calorie-dense foods. This is particularly true on a keto diet, as many of the best keto foods are high in fat and calories. Or, perhaps you eat processed junk food, which won’t help your health or waistline at all.
There’s one other issue too. When you’re fasting, your body thinks that it needs to conserve energy. This can decrease your metabolism and make weight loss more difficult.
So, if you’re fasting often, eating large meals during your eating periods, and making poor dietary choices – fasting could easily make your weight problems worse, not better.
Can Create Unhealthy Eating Behaviors
Many people struggle with the relationship between them and food. It’s already far too easy to view food as the villain and even feel guilty any time you eat. Patterns like intermittent fasting can make this much worse.
You might even find that you try to eat relatively little during your eating windows as well, perhaps so you lose weight faster.
This isn’t the intent of intermittent fasting at all. Instead, the aim is to still enjoy food – just at specific times. Many intermittent fasters find that their enjoyment of food even increases and they make healthier choices about what they eat.
If you fall into the second group, then intermittent fasting could be a good choice. But, if you try it, and find that you’re avoiding food even during eating periods or that you struggle with the approach – then intermittent fasting probably isn’t the best choice.
And, if you have a history of disordered eating already, it's best to steer clear of intermittent fasting entirely. Trying intermittent fasting in this situation is simply too risky.
Fasting Can Be Dangerous
There’s this old idea that fasting for long periods or eating very little is fine because our bodies have stores of fat to use for energy. It’s an easy idea to buy into, especially if you’re overweight, but doing so could be dangerous.
While fasting does allow us to use stored resources for energy, our bodies don’t store all of our consumed nutrients in the same way. So, relying on stored fat rather than food could easily lead to nutrient deficiencies.
Fasting can be dangerous in other ways, particularly if you have an underlying health condition or are fasting for long periods at a time. Because of this, it’s always important to keep an eye on how your body responds. Keeping your doctor informed can help too, as he or she will be able to spot any serious issues early on.
What Can You Eat?
Intermittent fasting focuses on when you eat, rather than the specific types of food. For the most part, you can eat anything you like during feeding windows and nothing at all during fasting windows.
The main exception is if you’re doing low calorie fasting, where you’re eating 500 calorie meals instead of doing a true fast.
However, having a free-for-all during your eating window won’t do you much good at all. It’s still important to think about the type of food you eat and your serving sizes.
The best approach is to focus on nutrient-dense foods, including foods that are rich in protein and healthy fats. This is especially true if you’re eating fewer meals than normal, as you need to keep your nutrient intake up.
Pay attention to your calorie intake too. When you’ve been waiting all day to eat, it’s too easy to overload your plate.
Some people get around the problem by planning their meals carefully. This helps to make sure that they get enough nutrients without overdoing it in any area. Planning meals like this is particularly important at the beginning, as the hunger and energy signals from your body may be confusing.
You might also combine intermittent fasting with some type of eating plan, like the Mediterranean diet, keto, paleo, or veganism. Doing so can be effective, but you need to pay close attention to how your body responds.
Diets like keto and paleo are particularly significant, as these are both restrictive. Combining a restrictive diet with restrictive timing for meals could be too much for many people. The combination also increases the risk of disordered eating or not getting enough nutrients – so tread with caution.
How Strict Do You Need To Be?
In theory, the stricter you can be with your fasting windows, the better. Some of the benefits are specifically related to being in a fasted state. Even having a few nuts to stave off hunger may decrease the benefits that you see.
Still, this isn’t a cut-and-dry topic.
Strict diets are rarely ever successful in the long term. It’s too easy to go off track, especially if you’re giving up your favorite foods or activities along the way.
As various writers have pointed out, you don’t lose all you’ve gained simply because you take a few days off or have a snack at the wrong time. Sometimes it might be worth ignoring your eating window for a day to have lunch with a friend or to go to a wedding.
Similarly, if you’re feeling light-headed or sick because you’re hungry – then eat. Intermittent fasting or not, listening to your body is crucial for your health. Similarly, if you have a highly stressful week at work, it might be best to postpone your fasting, so that you can function optimally.
You can also tweak your approach based on what you’re hoping to gain.
For example, if you’re using intermittent fasting as a way to cut down your calorie intake, then you don’t lose much by adding milk to your coffee or having a snack on a day where the fasting period simply feels like too much.
In the end, if being less strict helps you to stick to intermittent fasting in the long term, then do so. You can always improve how well you follow your schedule as time goes on.
Who Shouldn’t Fast?
While intermittent fasting offers many potential benefits, it isn’t a good idea for everyone. Some people may need to avoid fasting entirely, while others might be better to stick to a gentle fast.
People in the following groups all need to be cautious with fasting. The idea might still be healthy, but you’ll often need to talk to your doctor first and plan carefully.
Anyone under 18. Children need nutrition to grow and fasting can jeopardize their nutrient intake. Fasting can also set up an unhealthy relationship with food, one that can follow the child for much of their life.
People with a history of disordered eating. If your history includes bulimia, anorexia, obsessive dieting, or fear around food, intermittent fasting might not be safe. At the very least, you should have a therapist on hand to help you work through any issues. Otherwise, there’s a risk that fasting will promote fear of food and make such issues worse.
Anyone with a poor diet or lifestyle. If you focus on processed food, aren’t getting enough sleep, are stressed, feel overwhelmed, or anything similar – then fasting probably isn’t the right choice. It’s much better to get everything else lined up first before you start trying to fast. Otherwise, you risk being more stressed and you won’t see nearly as many benefits.
Pregnant women. While many pregnant women can fast safely, fasting isn’t advised for pregnant women with a high-risk pregnancy or who struggle with nausea, weakness, anemia, or dehydration. Even healthy women should stop fasting if it is negatively affecting them.
Some people with chronic health conditions. Intermittent fasting can be helpful or benign for some chronic health conditions, but harmful for others. This is particularly true if your health condition or medication is influenced by the food you eat.
If you’re highly active. Fasting means your body has less fuel for a little while. This isn’t a good plan if you’re highly active or are training regularly. In those cases, your body will need regular energy input.
If you fall into any of these groups or are at all concerned, it’s best to talk to your doctor before starting a fasting regime. They should have a better sense of what is healthy and safe for. They might even have suggestions about how to optimize the fast for your needs.
Don’t forget to pay attention to your body. While many people thrive on intermittent fasting, some don’t. If you feel like you’re
At its heart, intermittent fasting is simply a way to approach meals. It’s the opposite of grazing strategies, where you are eating small meals frequently throughout the day. The idea works exceptionally well for some people, making weight loss easy and providing many benefits.
People in this situation often find that they get energy from their fasting periods. The process gets easier as well. Once you’ve been intermittent fasting for a while, the fasting windows may not feel like a big deal at all.
Others find that they’re constantly hungry, stressed, and moody, and are always waiting for when they’re allowed to eat again.
If you fall into this second group, then intermittent fasting mightn’t be a good fit. After all, the goal is to find a healthy lifestyle, not another fad diet. You’re not going to achieve this if your eating approach feels like torture from start to finish.
Don’t forget that your eating frequency is only one part of the equation. To truly thrive, you need to make sure that you also focus on healthy foods and drink plenty of water.