Intermittent fasting for fat loss

Intermittent fasting is an easy and convenient method of weight loss (or specifically fat loss, since we don’t want to lose muscle mass). However, it can be confusing and often seem overwhelming. If you want to try it out, this article will cover the easiest and safest way for you to start.

What is intermittent fasting?

Intermittent fasting is changing when you eat, and not what or how much you eat. Intermittent fasting is the act of reducing the hours of the day you can eat, and increasing the time you cannot. These are called the feeding window and fasting window respectively. There are several types of fasting, but for the purpose of fat loss, this article will only look at fasts less than a day. Fasting for more than one day is typically for longevity, and is something that you should only look at once you have a stable fasting regimen.

How does intermittent fasting work for fat loss

There are two reasons intermittent fasting for fat loss works:

First, because you have a smaller eating window, you end up eating less frequently. When you eat less frequently, you also tend to eat less overall.

Moreover, it stops snacking, which is one of the biggest sources of excess calories that lead to fat gain. In the Four Hour Body, Tim Ferriss shows from his experiments that optimum fat loss is the result of a maximum of two blood sugar spikes above 100 per day. Ideally, you want to have two meals or less.

This is why people who start intermittent fasting as the only change often see fat loss quite quickly.

Second, when you fast for more than 12 hours, you also start tapping into your fat stores for energy. The longer your fast is beyond 12 hours, the more of your stored fat loss you will consume. Once you have stable fasting practice, you can then increase the efficacy of that fast with exercise. Scroll down below to see the different fasting windows and how long it takes to move from one to another.

Overall, there are metabolic benefits to fasting that far outstrip the weight loss that comes with it. You can go forward knowing that you are not losing weight to become healthy, but your improving health is the real cause and the weight loss is coming along for the ride.

How to begin intermittent fasting for maximum fat loss

Step #1: Start intermittent fasting as gradually as possible.

This is critical if you have blood sugar issues and/or some form of insulin resistance. Don’t go straight into 20 hour fasts, start slow and increase gradually. This way you reduce the risk of headaches, fatigue, and possible dizziness. If you feel bad from the outset, you probably won’t maintain this for the longer term.

Like I said before, this is the safest way to start intermittent fasting.

Before you start, take measurements, photographs, and your weight for comparison later. This is important, as seeing progress is motivating.

Step #2: switch to only three meals a day, no snacks.

If you snack regularly, this will be a noticeable difference. Your meals schedule will look like the typical breakfast, lunch, and dinner. You won’t consume anything with calories before breakfast, between meals, and after dinner.

Step #3: Reduce it down to two meals a day.

What would this look like? one example is to skip breakfast, have an early lunch, and a late dinner. It won’t take long to find a schedule that works for you. When this feels normal and you have no issues, you can move on to the next step.

Step 4: Start shrinking the eating window gradually.

Pair the reduction in your feeding window with improvements in your diet and you will start to see more benefits. Remember, intermittent fasting is not an excuse to eat whatever you want in the feeding window. Eat too much of the wrong things during the feeding window and you can gain weight.

I started with a 12 hour feeding window. I maintained this for about a week, and then went to 14 hours, and ultimately about a month later, I hit 18 hours. Now my fasting goes from 14 to 18 hours with the occasional 20 hour fast.

Dealing with headaches and fatigue when you first start intermittent fasting

If you look at people’s experience online with fasting, one of the most common reasons for quitting are headaches, fatigue, and generally feeling miserable on a fast. One reason is people go from three meals and snacks straight to a 16 hour fast. As I mentioned above, start slowly and progress slowly.

Another reason are low electrolytes or dehydration. When fasting you can lose a lot of stored water, so prepare yourself to drink more water than normal. You also lose a lot of electrolytes, so you can try increasing your salt intake or try consuming a zero calorie electrolyte drink/powder during the fast.

The different fasting periods

Here is a list of the most common fasting periods:


This the most common starting point, and is also the same time period people use when doing a type of intermittent fasting called circadian rhythm fasting, which is fasting from sunset to sunrise.


If 12 hours is the most common starting, this is the most popular intermittent fasting duration. Here you fast for 16 hours and limit your feeding window to eight hours. The placement of those eight hours varies from person to person. You can have lunch at 12 noon and dinner at 7pm, or a late lunch at 2pm and dinner close to 10pm.


Some consider this the most optimal fasting duration, where you limit eating to just six hours. You still consume two meals with this program.


We shrink the feeding further here, down to four hours. This increases fat loss, and since its hard to eat two large meals in such a short period of time, your total calorie intake is likely to drop further.


OMAD, also known as One Meal A Day, is almost a 24 hour fast, where you eat a single large meal in a short feeding window. This is harder to do for most people, and even so, is not a protocol you should follow daily.

What is the best schedule for intermittent fasting?

There is no single best length of fasting better than the others. Overall, the longer you fast, the more fat you will burn. However, the best fasting schedule is the one you can manage for the long-term. Do you get tired or feel too hungry with a specific fast? then experiment with longer and shorter fasts. Remember to always increase your fasting window gradually.

Why is it worthwhile to change what you’re eating?

There is a lot of research into intermittent fasting, and specifically time restricted feeding. There are clear metabolic benefits, and fat loss is almost certain for most people. However, optimal fat loss, especially over the long-term, largely depends on the composition of your meals during the feeding window.

The biggest mistake that people make when fasting is that they think they can eat whatever they want. This is not true for the vast majority of people. Although some people get away with it because of their level of physical activity and current metabolic health, a lot of people will end up putting on more weight.

The fasting zones

There are four zones or stages of intermittent fasting. If you want to optimize for fat loss, you want to move to the fat burning state as fast as you can, and stay there for as long as you can.

Anabolic zone

0-4 hours

Your primary source of energy during this time period will be from your last meal. This is the best time to work out, especially if you want to build muscle. You will also feel the best working out during this time.

Catabolic zone

4-16 hours

Your glucose levels will continue to drop and so will levels of insulin. When your glycogen stores get low, your body will switch to using stored fat.

Fat burning zone

16-24 hours

Your brain will still need glucose to function so your body will convert other non-carb sources to glucose for your brain. The rest of your body will switch to fat for fuel. If optimal fat loss is your target, remain in this zone for as long as possible.


24+ hours

How to get into the fat burning zone as quickly as possible?

There are two ways to get into the fat burning fasting zone quickly.


The more carbohydrates you consume, the longer it will take to burn through those, then deplete your glycogen to start burning fat. The best and most effective way we know so far is to switch to a low-carb high-fat diet. Beginners should transition slowly since we first want to build up a fasting habit.


You can move through the zones faster with exercise. However, early on you might want to avoid working out in the anabolic window, because too much depletion can result in late night hunger pangs. Many find that the best time is in the morning, during the catabolic window with low intensity aerobic workouts like Zone 2 training. Even long morning walks would help.

Which fasting zone is best for exercise?

You can and should exercise during all zones of the fast. However, your performance will vary depending on which zone. Depending on the type of workout certain zones will be more appropriate. Exercise is also a great way to accelerate your progress from one zone to another.

Build muscle

If you want to build muscle, then you should do so in the anabolic fasting zone. This zone is directly after a meal, when you have elevated insulin and glucose levels. This could be after your first meal of the day or your last.

Fat loss

If you want to preserve lean mass and want to lose weight, you do the workout in the morning during the fast. You accelerate the catabolic state and move into the fat burning state faster. You will generate enough net leucine to preserve muscle tissue but you wont gain muscle. In a shorter fast, If the goal is to preserve or gain lean mass, workout before the refeed. The drawback is that you will feel crappy the longer the fast.

High intensity

With high intensity workouts you can quickly deplete glycogen and take you to the next zone faster. In a longer fast, high intensity training will suffer. Workouts that are glycolytic will suffer after depletion.

Why is intermittent fasting for fat loss so easy?

Because of its simplicity. You wake up in the morning and don’t eat anything until lunch. Though I often have a cup of black tea or black coffee. Then, I stop eating or drinking anything with calories after dinner.

How to avoid the biggest danger when intermittent fasting

One of the biggest danger and mistakes people make when intermittent fasting, especially when they start seeing results, is not eating enough calories during the feeding window. Your fat loss will come from metabolic improvements and spending time in a fat burning state, and while it is good to occasionally drop your total calories, running a low calorie diet and fasting for extended periods will not end well. My advice: keep a meal diary at the start and occasionally check in and make sure that you are getting enough calories.


Intermittent fasting is much easier than any popular fad or crash diet that comes to mind. Why? the rules are simple, eat only at lunch and don’t eat after dinner. As a protocol for fat loss, intermittent fasting remarkably easy to follow and even easier to stick to, should you follow the basic rules.

Common questions and answers

Should you supplement while fasting?

There is no evidence to show that vitamin supplementation helps unless there is a deficiency. However, since fasting can involve less food than you normally consume, it can also mean less vitamins and minerals. You probably don’t need to supplement if you get a lot of vitamins from your diet and did not take any supplements to begin with. What you will probably need and will find helps with fasting are electrolytes such as Sodium, Potassium, Zinc, and Calcium.

Why am I not losing weight even after intermittent fasting?

All thing being equal it is probably too much food intake. We tend to underestimate how much we eat when we are trying to lose weight. As a result, your first step should be to look at what you eat and how much of it you are eating. Potion sizes are also a common cause for weight gain during a fast.

Is Intermittent Fasting bad long term? Should you fast every day?

There are no known long term side effects for fasting, however, it is a good practice to vary your fasting windows on a regular basis. For example, once you get comfortable with longer fasts, alternative between 12, 14, 16, and 18 hour fasts.

How much weight can you lose in a month with intermittent fasting?

There are studies that have shown 0.25 to 0.75kg weight loss per week, but the true figure is specific to the individual. Also, you might lose fat and add lean mass, so always use more than one method of judging any changes, like before/after pictures, multiple measurements, and even how your clothes fit.

How long before you see results from intermittent fasting?

It varies, for some it can takes weeks or even a couple of months, for others you will see an immediate drop and then small improvements over the next few months. Intermittent fasting is going to improve your metabolic health and should you maintain that, you will lose fat eventually.

Is there an optimal window for fasting?

The optimal window for fasting is the one that you will be able to continue for the long term. Is a 6pm dinner too early for you? both in terms of night time hunger or social implications. If you will a specific window is working for you, stick to it, but don’t be afraid to change it around.

Is Intermittent Fasting bad for your heart?

On the contrary, it has been shown to improve heart health. The American Heart Association reported on two studies showing that intermittent fasting “is associated with lower rates of heart failure and a longer life span.”

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