Fasting isn’t required to lose weight on a ketogenic diet. If it doesn’t work for you, then do not force yourself to fast. Restricting yourself unrealistically is pointless – it’s not worth it if it makes you unhappy.

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However, you are probably wondering how there could possibly be a benefit to eating less frequently that goes beyond what you are already getting with a ketogenic diet. Restricting carbs and eating enough fat and protein does come with a plethora of health benefits, but when you add intermittent fasting to your lifestyle you can increase energy and reverse aging by harnessing the power of a process called autophagy — the process by which the cell devours itself. Superficially, this sounds like a terrible thing for our cells to do — until you consider what is really taking place.

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When our cells undergo the process of autophagy, non-essential parts like damaged proteins are recycled and invading microorganisms and toxic compounds are removed. This means that autophagy plays an important role in stopping the aging process, reversing disease, and preventing cancer, but it doesn’t happen all the time. Fasting, protein restriction, and carbohydrate restriction are the three main ways that can initiate different autophagic processes — all of which are not the same. This is part of the reason why a ketogenic diet has so many positive effects, and it also shows you why IF is a way to improve your diet even more.

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When you fast, human growth hormone levels go up and insulin levels go down. Your body’s cells also change the expression of genes and initiate important cellular repair processes.

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As you get used to fasting, you should start to fast naturally. Meaning, only eat when you’re hungry. Don’t plan your fasting – let it happen naturally.

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People are always saying that if you don’t utilize the importance of pre and post workout meals, you are going to be losing muscle when you work out.

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This isn’t necessarily true, and it is even less so when you are adapted to ketosis.

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Fasting while training can lead to a number of benefits in the long run, including:

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• Higher metabolic adaptations – Studies show that your training performance will increase in the long run when you are exercising in a fasted state.

• Improved muscle synthesis – Studies show that muscle gains are heightened when you train in a fasted state and utilize proper nutrient intake.

• Improved response to post-workout meals – Studies show that the speedy absorption of nutrients after a fasted workout can lead to better results.

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However, keep in mind that the main reason for its success is that intermittent fasting helps you eat fewer calories overall. If you binge and eat massive amounts during your eating periods, you may not lose any weight at all.

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In my opinion, one of the main benefits of IF is the simplicity of it.

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I personally do the 16/8 method, where I only eat during a certain "feeding window" each day. Instead of eating 3+ meals per day, I eat only 2, which makes it a lot easier and simpler to maintain my healthy lifestyle, even more when I'm travelling and don't have time to cook nor keto food available.

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The single best "diet" for you is the one you can stick to in the long run. If intermittent fasting makes it easier for you to stick to a healthy diet, then this has obvious benefits for long-term health and weight maintenance.

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Nearly all studies of IF have been conducted for weight loss purposes (4).

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It is important to realize that without exercise, weight loss will usually come from a loss of both fat mass and lean mass. Lean mass is everything besides fat, including muscle (5).

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This is true of weight loss caused by both intermittent fasting and other diets.

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Because of this, some studies have shown that small amounts of lean mass (1 kg or 2 pounds) may be lost after several months of intermittent fasting (4).

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However, other studies have shown no loss of lean mass (6, 7).

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In fact, some researchers believe that intermittent fasting may be more effective for maintaining lean mass during weight loss than non-fasting diets, but more research is needed on this topic (8).

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Overall, it is likely that IF will not cause you to lose more muscle than other weight loss diets.

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One study showed that intermittent fasting causes less muscle loss than regular calorie restriction (9).

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Studies show that short-term fasts actually boost metabolism (10, 11). However, longer fasts of 3 or more days can suppress metabolism (12).

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There is very limited research on whether or not it is possible to gain muscle during IF.

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However, one study of IF and weight training provides some preliminary information about muscle gain (13).

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In this study, 18 young men completed an 8-week weight training program. They had not previously performed weight training on a regular basis.

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The men followed either a normal diet or a time-restricted eating program. The program required them to consume all their food in a 4-hour period on 4 days each week.

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By the end of the study, the time-restricted eating group had maintained their lean body mass and increased their strength. However, the normal diet group gained 5 pounds (2.3 kg) of lean mass, while also increasing their strength.

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This could mean that intermittent fasting is not best for muscle gain. This may be because the time-restricted eating group consumed less protein than the normal diet group.

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There are a few other scientifically based reasons why IF may not be optimal for gaining muscle.

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In order to gain muscle, you must eat more calories than you burn, have enough protein to build new muscle tissue and have a sufficient exercise stimulus to cause growth (14, 15, 16).

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Intermittent fasting could make it difficult to get enough calories to build muscle, especially if you are eating nutrient-dense foods that fill you up easily (17).

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Additionally, you may have to make a bigger effort to get enough protein when eating less often than with a normal diet.

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All of these reasons don’t necessarily mean that it is impossible to gain muscle with intermittent fasting, but that it may not be the easiest diet for gaining muscles.

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Even among those who use intermittent fasting, there is debate about whether or not to exercise when you are fasted. Several studies have also looked into this.

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One 4-week study followed 20 women performing fasted versus non-fasted exercise on a treadmill. Participants exercised three days per week for one hour per session (18).

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Both groups lost the same amount of weight and fat, and neither group had a change in lean mass. Based on these results, it may not matter whether or not you exercise fasted if your goal is weight loss.

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However, it is possible that training fasted could impair your exercise performance, particularly for serious athletes (19).

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For this reason, studies of intermittent fasting and weight training have not used fasted exercise (20, 21).

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Overall, it seems that exercising while fasted may be a matter of personal preference.

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It will probably not make your exercise more effective, and it’s even possible that exercising fasted will decrease your performance.

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I only exercise in a fasted state (before my first meal of the day) if my main focus is to lose fat.

 

In my case, I see in my body that fat loss is more effective when I exercise while fasted, with only some minor downsides regarding my lifting performance if I keep my diet well balanced in ketogenic terms (75% fat, 20% protein, 5% carbs). 

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However, I don't recommend training intense cardio while fasted because it can be harmful for your body if you get in an overtraining state. It can ruin your immune system, cause insomnia, affect your appetite and release cortisol (the «stress» hormone), which in turn can make you more likely to put on fat. 

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Fasted slow paced cardio in the morning is effective because as you sleep and fast overnight your body conserves its precious carb stores and leans toward mobilizing fat for fuel. The story doesn't end here, however. Your body also breaks down amino acids into glucose overnight, so fasted morning cardio mobilizes more fat and potentially more amino acids for fuel, which isn't ideal if building muscle is your primary goal. 

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I definitely recommend only doing intense cardio, using for example the HIIT (High Intensity Interval Training) method, between your eating «window» on a keto diet to prevent any harmful consequences for your health.

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Care needs to be taken when breaking a fast so as not to overburden your digestive system. The best benefit of fasting is realized when a fast is broken properly.

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Therefore, to break your fast you should follow a few guidelines. Here’s why:

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• While fasting, your metabolism is in a distinct state in which you undergo many hormonal and physiological adaptations, such as increased growth hormone, elevated luteinizing hormone, which promotes testosterone and you also trigger autophagy – the cells’ self-digestive mechanism.

• While fasting you’re also in a state of ketosis, which makes your liver convert fatty acids into ketones and energy.

• Most importantly, your intestines and gut have adapted to the abstinence of food, thus preserving digestive processes. So, to not put too much stress on your gut or to not cause excess inflammation, you can’t just start eating whatever.

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Research has also shown that consuming high amounts of carbohydrates may cause an abrupt weight gain. The reason for that is sodium retention.

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While fasting you excrete a lot of water and refeeding on carbs causes antidiuresis of potassium and sodium. You’ll get bloated but you may also have an energy crash of insulin.

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Therefore, you want to ease into eating the right foods at the right time when breaking your fast.

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It also depends on how long you’ve been fasting for. If you’re coming off a 5 day fast, then you need to be more patient than you would when just doing daily intermittent fasting with 16 hours fasted.

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Let’s start off with the average situation where you’ve been fasting for about 16-18 hours and you’re nearing the finish line.

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Now that you’re about to break the fast, you want to consume something that stimulates the digestive tract without releasing insulin:

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• Apple cider vinegar is perfect for this – it balances healthy pH levels, kills off bad bacteria in your gut, stabilizes blood sugar and improves overall health. You can drink a glass of apple cider vinegar during your fast. But it’s a great drink for breaking it as well. Here’s what I do before eating any meals.

  • 2 tbsp of raw apple cider vinegar

  • 1 half of lemon squeezed into hot water

  • 1 pinch of cinnamon for better blood sugar stabilization

  • 1 pinch of sea salt

 

Alternatively, you can do this without apple cider vinegar as well and just use hot lemon water.

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In any case, you want the citric acid from lemons to promote the creation of digestive enzymes in the gut before you eat.

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After that, you can also drink some bone broth. Bone broth is amazing and super good for you because it has a ton of electrolytes but it’s also packed with collagen:

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• Collagen protein is what most of your body is made of – your joints, nails, hair, skin – it helps to keep you more youthful and elastic.

• Drinking bone broth after your fast will also help you to absorb the other electrolytes and minerals a lot better. Your gut has been cleaning house for a while and is now ready to utilize the nutrients from the bone broth as well as the foods you’ll be consuming afterward.

 

If you’ve been fasting for over 20 hours, then it’s a good idea to drink some bone broth or some soup before you eat anything solid.If you’ve fasted for just 16 hours then it’s not that important but still a good idea.

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An alternative for bone broth is also fish broth.

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You cook up all the leftover bits of the fish, like the head, the fins and bones so you could get all those extra omega-3 fatty acids, which are tremendously good for your brain and heart health. I mean, don’t just throw away these foods when there are still so many unused nutrients on them.

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If you don’t have access to bone broth but you still want to give yourself some immediate energy without crashing, then you can also consume some MCT oil.

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MCTs get converted into energy faster because the fatty acids in it bypass the liver and go straight to the blood stream.

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This is beneficial because you’ll also prolong the effects of fat burning and stay in ketosis for longer even after having consumed calories.

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After you’ve drunk your lemon water and maybe bone broth, then you should wait for about 15-30 minutes to let your gut absorb the nutrients.

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You might feel your intestines waking up, which is a good thing.

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I recommend your first meal should be something small and low glycemic, no matter what diet you’re on. This will keep you in a semi-fasted state because of the non-existent rise in blood sugar.

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You don’t have to worry about muscle loss either because ketones are protein sparing. Fasting already puts you into mild ketosis, but if you drank bone broth or MCTs, then you’re not going to cannibalize your own body.

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Some examples would be:

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• 2-3 eggs, half an avocado, some nuts and spinach

• 1 can of sardines with some salad and olive oil

• I wouldn’t recommend you break your fast with red meat because it’s more difficult to digest than eggs or fish. Meat products should be eaten as your second meal.

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Now you know that there is nothing to fear when it comes to intermittent fasting. Although you will feel hungry at first, your body will adjust by activating autophagy and burning more fat and ketones for fuel.

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Water, coffee, tea and other non-caloric beverages are fine to be consumed while fasting. Do not add sugar to it. Coffee can be particularly beneficial during a fast, as it can blunt hunger.

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Intermittent fasting is not something that anyone needs to do. It’s simply one of many lifestyle strategies that can improve your health. Eating real food, exercising and taking care of your sleep are still the most important factors to focus on.

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If you don't like the idea of fasting, then you can safely ignore this method and continue to do what works for you.

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At the end of the day, there is no one-size-fits-all solution when it comes to nutrition. The best diet for you is the one you can stick to in the long run.

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Intermittent fasting is great for some people, not others. The only way to find out which group you belong to is to try it out.

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If you feel good when fasting and find it to be a sustainable way of eating, it can be a very powerful tool to lose weight and improve your health.

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This content does not constitute a medical consultation. I recommend you to see a certified medical professional for diagnosis.

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