Pros And Cons Of Intermittent Fasting

If you’ve been thinking about starting intermittent fasting for some time but are unsure of exactly what it brings to the table, you’re in luck, as in this post we will discuss in detail what the major pros of the intermittent fasting diet are.

But not so fast. As with anything in life, with the pros come the cons. As a wise superhero’s uncle once said “with great power comes great responsibility”. Okay, maybe that doesn’t fit the bill as well as we thought in our minds, but the key take away here is that you need to be well informed of what it can do for you as well at its potential downsides before plunging in headfirst.

You are going to be spending time, more likely than not – a long time – committed to this diet, so without further ado, ladies and gents, introducing the two sides of intermittent fasting.


1. Massive Weight Loss

Yes, massive weight loss is in the books for anyone who diligently applies their self to following intermittent fasting diet principles . Unless you are already a super fit, conditioned athlete, you likely retain at the minimum 15% body fat, often much higher if you’re a woman.

Depending on which variation of intermittent fasting diet you choose, you may lose weight rapidly or at a more controlled pace. But the bottom line remains that a significant weight loss is in your future.

2. No Counting Calories

One of the most resented aspects of dieting in general is the requirement of calorie counting. This is generally almost always required if you are trying to lose weight, and the reason many people fail to see sizeable progress in that regard.

Do you need to count calories while intermittent fasting? Not particularly. Yes, if your fasting day requires you to eat just 500-600 calories you WILL need to know what that looks like, but once you have established that there is scarcely a need to do it every time.

When it comes to the 16/8 variation of IF you are even less likely to need to count calories as a caloric deficit is almost always guaranteed. We hope you’re not a compensatory eater, however, or you could be in for a hard time.

3. Growth Hormone Levels Increase – Significantly

If you’re an athlete, growth hormone is best known to you to be able to promote lean muscle gain while simultaneously helping reduce body fat, bringing about a nice change in body composition. If, however, you’re more interested in overall healthy living, you would know growth hormone as the body’s fountain of youth hormone.

It is highly sought-after for its anti-aging effects, and the ability to rejuvenate cells, in effect being the closest thing to slowing down the clock that we currently have. But how does intermittent fasting cause hormone levels to increase?

It actually relates to another hormone, ghrelin, which is intricately tied to our hunger. As levels of this hormone rise, it causes you to feel hungry, and so in turn stimulates an increase in growth hormone production. Since intermittent fasting typically means you will go for a period of time without consuming food, the net result is increased synthesis of growth hormone.

Think of this as an adaptative mechanism that our bodies possess; cellular processes are slowed down (inclusive of aging) in response to caloric limitation with the goal of preserving life as long as possible.

4. Promotes Cellular Autophagy

Chances are you’ve never heard of autophagy before, even though this is a normal bodily process that goes on every single day of our lives. Under normal circumstances, it merely ensures that cellular components are recycled in an efficient manner, where they may then be used for other aspects of cellular production.

While this exact process occurs when we do intermittent fasting, an additional type of autophagy occurs – you can think of this as beneficial cellular cannibalism. What does this mean? In addition to the healthy, normal functioning cells, there are others that are damaged or aged. Under circumstances that mimic caloric restriction, or even starvation, the body rids itself of unnecessary cellular components, using them for sustenance when calories are scarce.

In the context of intermittent fasting this is not bad, as you will be consuming food again. Instead, it can be considered an easy reset button for ridding your body of damaged material which serves no other real beneficial purpose.

5. Reduces Heart Disease Risk

Heart disease is the number one cause of mortality in the world today, making it very important for you to take steps that mitigate your risk.

Intermittent fasting achieves this via multiple mechanisms, including a reduction in body fat, lowered blood pressure levels, enhanced glucose control by enhancing insulin sensitivity, and assisting with reduction in overall blood lipid levels.

Coupled with the fact that intermittent fasting reduces oxidative and inflammatory biomarkers (compounds such as homocysteine, superoxide in particular), and you significantly reduce the likelihood of you experiencing a cardiovascular episode in your lifetime.

Your risk of heart disease is related to the overall oxidative/inflammatory load of your body. This explains why people that consume diets that are considered highly inflammatory, contain low quality processed fats, sugar and are under chronically high stress are more likely to experience heart attacks or strokes.

Of course, to ensure that you take advantage of this generous insurance policy, you need to make the foods you do consume count, and be sure to get your exercise in.

6. May Reduce Cancer Risk Or Make Chemotherapy More Effective

Cancer cells are believed to use glucose as their primary energy source, but intermittent fasting diets actively reduce the amount available to them for a period of time. During this interval, the immune system may become more efficient in taking care of pre-cancerous cells, helping to enhance your evasion.

Alternately, certain cancer cell types have their growth retarded and subsequently become more susceptible to chemotherapeutic agents, improving your prognosis. It is important to understand that this benefit applies primarily to normal risk individuals, as you will read more about below.

7. Increased Brain Performance

Common sense would probably tell you that when you’re hungry your brain is likely to struggle to keep up, so what gives? While this isn’t completely wrong, the feeling of mental fogginess is only transient, and likely to pass in a week or two.

It comes down to the body’s degree of fat adaptation. Typical Western diet consumption patterns mean an over-reliance on carbohydrate (glucose) heavy foods for energy. Metabolic adaptations hence favor glucose for use as fuel, so when these levels run low, alternate macronutrients are not as efficient in producing energy – at least not initially.

However, as this sequence of events is repeated over the course of several days on end, the body starts to make adaptations so that it becomes more efficient at using the available nutrients it has to produce energy, which in this case is primarily fat.

After that initial week or two, the brain fog, lethargy, and irritability you have become accustomed to experiencing when glucose levels are low ceases to occur, and what you have is consistent brain performance as you start to use ketone bodies as an alternate fuel source more consistently.


1. Long-Term Compliance Is Difficult

There is a distinct difference between motivation and discipline that many people do not comprehend. Planning to start intermittent fasting diet this New Year to finally lose that extra 50 pounds? That’s motivation. However, the problem with motivation is that it is short-lived. The motivation you have to get started is by no means guaranteed to help you continue six months later.

Discipline, on the other hand it a conscious effort to do what you need to do day in and day out regardless of how you feel. Most of the people that are successful with intermittent fasting have discipline. Regardless of how crappy their day was, they do not resort to consuming sugary junk for the serotonin surge it brings.

Many people who start the intermittent fasting diet by the time they approach a six month mark either drop out, or are eating 25% more calories than when they started out. If you truly want to be successful with it, you must develop an iron will and discipline.

2. Your Social Life Will Suck

Do you regularly enjoy a night on the town with friends where you eat, drink and be merry? Then you’re going to be in for a challenge if you are serious about following an intermittent fasting protocol. Not only will you not have the luxury of being able to pick up yourself and just go out for your regularly scheduled overconsumption sessions, but other recreational consumables (think alcohol, hookah, and cigarettes) do not fit well with fasting.

Even if you do manage to go out when you are allowed to re-feed, the end result is likely to be just as unfavorable since you may blow calories out of the water and consume three days’ worth in mere hours.

3. Binge Eating

The human species appears to be driven by reward; we want something in turn for doing something good. While the reward in this case should be viewed as improved health and body composition, often times that reward is food.

After 16 hours of fasting you shouldn’t be capable of consuming the same amount of food, but even though we may not be hungry, for some reason we keep compulsively eating. This is a type of compensatory behavior to make up for all the time lost, and is one of the major reasons for failure.

Hunger appears to have a very strong psychological aspect in addition to being truly physical in origin, and explains why so many eating disorders are prevalent. There is no guarantee this will happen to you, but it often occurs with no clear trigger in sight.

Known triggers, however, may include anxiety, stress and sleep deprivation. This is why we mentioned in our other post to consider your overall lifestyle when choosing a suitable IF model to follow.

4. May Increase Cancer Risk

This is a tough pill to swallow, especially since one of the very pros of the IF diet is also reducing cancer risk, so what gives? In a nutshell, it comes down to individual susceptibility, or genetic predisposition.

If you have significant evidence of familial cancer, especially in first-degree relatives, IF may inadvertently increase your risk. How so? It relates to the very hormone that is extremely beneficial; growth hormone.

Growth hormone also stimulates another very anabolic (tissue building) hormone in the liver known as IGF-I (insulin like growth factor 1). While this hormone helps with rejuvenation of damaged cells and in turn helps you stay younger, they also do the same to cells with cancerous potential. This means that instead of being destroyed by the immune system, they may be allowed to grow.

Truth be told intermittent fasting isn’t the primary culprit at hand here, since genetic risk seemingly increases the danger regardless of what you do. This is even evident in athletes who consume an immense amount of calories inclusive of proteins and carbohydrates to stimulate the very same anabolic hormones which promotes lean muscle accrual.

5. May Not Be Appropriate For Diabetics

Even though intermittent fasting is an excellent way to improve blood sugar management, fasting for extended periods of time can also prove troublesome and lead to hypoglycemia, or low blood glucose levels.

Diabetics usually have an overabundance of glucose circulating in blood at any one time, but are usually unable to make use of it due to insulin resistance or lack of completely. Intermittent fasting slowly improves insulin’s function, which means that unless you are keeping a close eye on blood glucose levels throughout the day, you could be reducing the levels to unsafe thresholds over time.

It becomes even more challenging if medication prescribed by physicians need to be taken with food, as taking alone they may have catastrophic effects. Why? Because anti-diabetic medication (either in the form of pills or injectable insulin) work to actively reduce blood glucose levels. When you have gone several hours without food, blood glucose is already low. The result is hypoglycemia, a condition that can lead to fainting, disorientation, coma or even death if carbohydrates are not replenished.

6. Impaired Physical Performance

If you are a high-performance athlete, intermittent fasting could take a toll on your performance, especially if fasting involves going a day straight with no calories, or a minimal amount (such as in the 5:2 and Eat Stop eat diets).

Maintaining a high level of performance mandates the use of the best fuel available, which turns out to be glucose. Yes, fat adaptation does yield consistent production of ketone bodies, but these alternate fuel sources are not as efficient as glucose for generating ATP.

Ketone bodies should thus be considered as efficient enough to power low to moderate intensity activity, but not enough for Elite level athletes.

7. Not A Good Idea To Follow Intermittent Fasting If Pregnant

We know it can be harrowing to see your weight creep up to levels you never thought imaginable while pregnant, and we know it can take a toll on your self-esteem. Sometimes, in desperation you may be tempted to try methods that are not a good idea, which in this case turns out to be intermittent fasting.

During pregnancy, and for a little while after if you are breast-feeding, your body needs more calories to be able to meet increased energy requirements of pregnancy, or to ensure that adequate production of milk is met.

Intermittent fasting will not only create a significant caloric deficit regardless of the model you decide to follow, but can complicate you delivering a healthy child as it can also open up several micronutrient deficiencies.

For instance, folic acid is important for the development of a fetus’ brain and neural system while in the womb; likewise is calcium to ensure bone formation. Iron and B-Vitamins help to support synthesis of red blood cells – all very critical during pregnancy. IF can adversely affect the supply of these nutrients and contribute to the likelihood of a birth defect, or worse, occurring.

At this time, patience is your strongest weapon. Think of the bustling bundle of joy you will be gifted within a few weeks/months, and then shortly after that, the MILF body you will be proud to flaunt!

In Summary

It is important to appreciate that intermittent fasting diet can help deliver significant benefits for your health, but at the same time not be oblivious of scenarios that may make it not a good fit.

If you’re still unsure of if it is right for you, be sure to speak with a dietitian, sports nutritionist or a medical practitioner to devise the best way forward.

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James Dixon

James Dixon is a fully qualified personal trainer and award winning writer, with a decade’s worth of experience under his belt. Throughout his career, he has helped hundreds of people to meet their dietary and fitness goals, writing exercise and nutrition plans to suit any and every requirement.

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