Intermittent Fasting Can Help You Lose Weight, But is it Right For You?


Is intermittent fasting right for you? Finding out how you feel about carbohydrates is a great starting point in making your decision. While you may have concerns about going on a completely ‘no carb diet’, there is no real harm in trying not to eat carbohydrates for a week or two in order to ‘reset’ your body’s insulin sensitivity.

In fact, this can be a great prelude to any diet if you have struggled in the past.

Another option during this time is to use something called ‘carb backloading’. This means that you can still eat carbohydrates but you’re only going to use them directly after exercise. The reason for this is that you will at this point be in an anabolic state while your muscles will be depleted of ATP and glycogen. If you consume carbohydrates at this point, then your body will use them to refuel the muscles and your energy stores rather than increasing fat (which is called ‘lipogenesis’ by the way!).

This is an example of ‘meal timing’ and how that can have a very important impact on the way your body responds to what you feed it. This is something that bodybuilders will often take into account for example hen trying to build muscle – they tend to eat protein at such a time that it will be absorbed into the blood stream in the ‘anabolic window’ that follows their exercise. This means the protein is readily available for the body to use as it repairs muscle fibers and builds muscle tissue. Another option is to consume a slow-release protein such as casein just before bed. This means you’ll have a steady protein supply during the night – which as you’ll recall is your most ‘anabolic state’.

Tim Ferriss, author of the The 4 Hour Body, recommends using a short amount of exercise one hour after eating if you ever ‘accidentally’ eat too many carbs in one sitting. By waiting one hour, you will be exercising just as the sugar is entering the blood stream. And by doing this, you can ensure that this energy is used up on exercise rather than being stored anywhere as fat!

Introducing Intermittent Fasting

Something else that can be very useful for a lot of people is to use intermittent fasting as a way to ‘fix’ insulin sensitivity and to increase your energy efficiency over all.

So what exactly is intermittent fasting? Basically, this means going for short periods of time without eating at all, which in turn can increase your energy efficiency as well as helping to reduce your overall calorie count.

One of the most popular examples of IF is the ‘fast diet’, also known as the ‘5:2 diet’. In this diet, your aim is to fast for two days of the week and to eat normally for the remaining five. During those two days, you aren’t going to completely eradicate all food though. Instead, you’re going to survive on just a very small amount of food at around 500-600 calories a day for women and men respectively.

This might sound like an extreme measure but it may surprise you learn that like the Paleo diet, this is actually closer to the way we would have eaten in the wild. In the wild, we would have spent days potentially tracking our prey and only feasting on occasional berries and nuts as we did. Then we would eventually kill them and have a supply that would last a short while. So our body wouldn’t get a consistent ‘three meals a day’ but would rather eat in fits and starts.

And this can then cause a number of positive changes in the body. For starters, if we go for a long time with very low blood sugar, it means that our activities will eventually use up all the available glucose in our system. Once all that is gone, it leaves our body with no option but to plunder our fat stores for useable energy. This means we’ll then burn more fat through all of our activities.

Fasting also forces our bodies to become far more efficient at using energy and burning fat. In particular, we see this in the increase of mitochondria – both their quantity and their efficiency. Remember, the mitochondria are the little energy factories in our cells that help us to convert ATP into useable energy. As we get older, the number and efficiency of our mitochondria decreases and this is one of the reasons young children have boundless energy and older people tend to just lie in front of the TV (a massive generalization… but you know what I’m talking about!).

When you exercise, you need to use more energy more efficiently and as such, you increase the number of mitochondria in your system. But this also happens when you go low-carb for a while, or when you go very low calorie. That’s because it forces your body to work harder to get the energy it needs. As a result, you start to feel less hungry and you get more energy from less food.

What’s more is that improved mitochondrial function can improve IQ (by providing your brain with more energy). And if you use exercise while fasting (this is called ‘fasted cardio’) your body is forced to burn much more fat and you will thus more greatly enhance your total calories lost. Some people do fasted cardio simply by working out in the mornings before they get their first meal.

And the holy grail is the benefit to your insulin sensitivity. Again, you’re forcing your body to make maximum use of every little bit of energy that comes into the blood. Thus, insulin sensitivity is ramped right up and you reduce your risk of diabetes.

Oh and one more thing – IF can also actually improve your cell’s efficiency. One of the big by-products of every energy system is oxygen and the less efficient your mitochondria, the more oxygen you release. Oxygen is highly reactive and when molecules roam free in the cells, they can react with cell walls causing wrinkles and the visible signs of aging. Eventually, this damage can burrow all the way into the nucleus of the cell where it can cause genetic mutations that cause cancer.

In short, IF can reduce the damage that oxygen does to your body and it can thereby improve your likelihood of cancer while slowing aging! Some people use calorie restriction to try and achieve the same thing (and drastically reducing calories has been shown in lab settings to help mice live much longer). Unfortunately, in reality this tends to lead to malnutrition as well – which is why using IF is a much safer way to enhance mitochondrial function and perhaps lengthen the lifespan.

Intermittent Fast Triggers Ketosis

Another reason to use IF is to trigger a state called ‘ketosis’. This is can also be achieved by very carefully controlling blood sugar levels – and it’s one of the goals of the misguided ‘bulletproof diet’ that we discussed earlier (with the coffee and the butter).

What ketosis essentially does, is to make your body better at burning fat for fuel, rather than burning carbs. You’re in ketosis when your blood contains a high-than-average quantity of ketone bodies, which means that lipid energy metabolism is in full swing and your body is now burning fat for simple bodily functions and activities like breathing or walking.

Ketosis helps make your energy system even more efficient and makes it particularly good at mobilizing fats for energy. What’s more is that ketosis spares proteins – meaning that it won’t burn muscle. Ketones also suppress appetite and it appears that they can provide a slightly better form of energy for the brain.

The Dark Side of Intermittent Fasting

Look, nothing is perfect and unfortunately intermittent fasting is also riddled with its own problems.

For starters, fasting also raises cortisol. Cortisol is the stress hormone and it is essentially the opposite of serotonin. Cortisol goes up when serotonin goes down and thus you have more cortisol in your blood when you wake up first thing in the morning. This makes you cranky and hungry and more likely to snack.

When you fast though, this cortisol goes through the roof and this can have numerous unwanted side effects. For starters, cortisol cannibalizes the muscles. It does this by increasing the production of myostatin – a substance that breaks down muscle (blocking myostatin is actually a way to massively enhance muscle building). At the same time, cortisol also encourages fat storage. In particular, cortisol encourages fat build up in the abdomen which is the unhealthy kind known as ‘visceral’ fat. While you can’t completely control the order that fat is added and removed from your body then, you can end up increasing belly fat by using any form of fasting. Oops!

Cortisol also has negative impacts on your thyroid hormones and actually blocks the ability for T3 to get into your cells. This means it slows down your metabolism and makes weight loss even harder. Oh and ketones are also toxic in high quantities and can ultimately lead to ketoacidosis.

What to Do

It might seem as though there is no clear cut answer here and that’s kind of the point. Unfortunately, if you’re someone who struggles to shift body fat then you’ll need to try lots of different methods until you find the one that works best for you.

Fasting is most useful for people who think that they might have insulin resistance and thus it can be a helpful tool at the start of a diet and as a way to increase sensitivity prior to starting that regime.

At the same time, you can also use the other type of intermittent fasting – by fasting for a part of the day. This way, you can enjoy some of the benefits of IF while making sure to also enjoy the benefits of surplus energy to enhance muscle building and other benefits.

Note as well that the full ‘5:2’ method of intermittent fasting is very hard for many people to stick with permanently and for that reason, you may have more luck with other methods.

About the Author

Justin Arndt is the author of the upcoming book Lose Weight Fast: The Science of Weight Loss. You can read more of his work at

Justin Arndt
Justin Arndt is the Senior Content Editor at Lose Weight Fast.