Intermittent Fasting – is fasting safe & does it work?

The current fashion for intermittent fasting for weight loss doesn’t seem to be abating. A quick keyword search for “intermittent fasting” shows a whopping 110,000 monthly online searches. Interest in intermittent fasting will wane as the next fad diet invests heavily to get all the media attention. Deep pockets generally only last so long in the absence of true and safe outcomes.

But is intermittent fasting a fad diet? Is it safe and does it work?

In theory calorie restriction, intermittent fasting included, can work if the number of calories consumed is regularly below the needs of that particular individual.

But so will being marooned on a desert island with nothing at all to eat, only fresh water to drink. This is the ultimate intermittent fast, albeit with a very prolonged time without food.

We’d all agree that this is easily labelled as “not a good diet to follow”.

A fad diet in the extreme.

Desert island - the ultimate intermittent fast - but is intermittent fasting safe and effective?

To truly assess the merits of any diet, including intermittent fasts, it is critical to understand the mechanisms of metabolism that result in weight loss.

Healthline is a site we have referenced previously. They medically review their articles by doctors, nurses, and subject matter specialists.

Their “6 Popular Ways to Do Intermittent Fasting” proves a valuable insight into what is intermittent fasting.

Even though Healthline say the articles are evidence based, some obvious discrepancies within this article point away from it being the authority on intermittent fasting.

That aside, the list is as follows:


  1. The 16/8 method
  2. The 5:2 diet (popularised by Dr Michael Mosely with the FAST 800 diet)
  3. Eat Stop Eat
  4. Alternate-day fasting
  5. The Warrior Diet
  6. Spontaneous meal skipping


What do they all these types of intermittent fasting diet have in common?

You don’t eat much or anything over variable but relatively short periods of time.

Unfortunately, this also means the periods of eating normally can be the times when free reign abounds.


Obesity - laziness and fast food?

For those battling obesity, eating "normally" or in other words excessively, is what has led to the increase in weight.

In our previous blogs we have discussed issues surrounding food addiction, but have yet to expand on the real food habits associated with obesity.

Obesity is caused by a consumption of excessive calories, consumed in a multitude of ways and driven by a number of reasons.

Forget the divisive and ignorant notion that all obesity is just caused by fast food and laziness.

Not all overweight people eat fast food. Forty million English people are not all lazy.

Binge eating

Although not universal, speak to people truly struggling with their weight and you are likely to hear stories of binge eating. Individuals eating restricted or controlled amounts of calories during the day and then consuming excessive calories in the evening.

Binge eating is a form of intermittent fasting, which is feeding obesity not curing it.

It is naïve to expect an overweight individual who is continually struggling to control their food intake easily adopt prolonged periodic control over food. In the long term our innate drive to eat simply cannot be controlled in this way for the majority of people.

It is therefore imperative to delve further.

Yes, to the advocates of intermittent fasting, there will be those outliers able to achieve long-term control, but we are talking 60% of the UK population here.

Intermittent fasting diets explained


The 16/8 method

To quote: “This method won’t work if you eat lots of processed foods or an excessive number of calories.”

We need not say any more.

The 5:2 diet (popularised by Dr Michael Mosely with the FAST 800 diet)

Dramatically cutting calories over just two days each week is flawed. A reduction of calories one day is likely to mean an increased intake the next as the drive to eat takes control.

The likely slow rate of weight loss will be a hinderance to diet success, and a potential lack of nutrition is a real concern.

Eat Stop Eat

The same concerns apply as for the 5:2 diet. We must not forget that we eat to supply more than just calories. Those similarly fasting for religious reasons often struggle both in terms of compliance and comfort.

Alternate-day fasting

Essentially this is an alternate day water fast. As with all the above intermittent fasting methods, simply turning on and off eating makes this alternate day principle rather worthless in the long run because it does little to counter the drive to eat.

The Warrior Diet

We will come back to the importance of food composition in more detail but the consumption of fruit, raw or otherwise during the day demonstrates an ignorance of the great deal of sugar fruit contains. A huge meal at night is ignoring a big driver of obesity!

Spontaneous meal skipping

Are we to believe that almost every person who has tried to lose weight has never tried to skip meals ad-hoc? This simply doesn’t work and its association with intermittent fasting further decreases the overall method’s credibility.


Intermittent fasting for weight loss is a bad idea.

Prolonged, continuous, supplemented fasting, is however safe, effective and the only metabolically sound method for dealing with serious weight problems as we will discuss now…


A summary of dieting metabolism

To help understand what happens whilst dieting, we’ll give you an analogy.

Our body fat is the body’s “energy savings account”, whereas glycogen is the body’s “energy current account”.

For our analogy our “energy cash” is that circulating and freely available in our body, supplied by the food and drink we consume.

It is important to note that current meals mostly contribute little to the immediate ongoing biochemistry.  Digestion, absorption and metabolism are not instantaneous processes.

Glucose is the human body’s primary energy currency used by all cells of the human body.


The human brain is the organ requiring the most energy and therefore lots of glucose. This is easy by just using some of our energy cash. In addition, when our cash runs out, the body is perfectly happy to support the drop in available blood glucose by utilising its store of sugar, called glycogen. The building blocks of glycogen is glucose.

Instigate a fast of a few hours, as in intermittent fasting, and the utilisation of glycogen may result in a drop in body weight. Success? But hang on, the majority of the weight loss is purely down to the associated water released when using up glycogen. Not so great since the next meal, whether 16 hours or 24 hours later, will simply top up the glycogen ready for the next time it is needed. If there is a tiny loss of fat (depending upon requirements) it is barely registered. The available fat in the circulating blood is relatively low. The vast majority of the lost weight is regained each time the short period of fasting is followed up by normal or near-normal eating.

The normal human body on a normal diet stores enough glycogen to fuel us for days even with a zero intake of calories. Intermittent fasting, regardless of the method, will simply not deplete glycogen reserves fully.

Great news you may think. We get to keep our back-up store of glucose as glycogen!

But hold off the celebrations, it is our fat stores that we need to deplete for real weight loss.

Our body not only stores extra calories as glycogen but also as body fat. Apart from our requirement for essential fatty acids, the fat we eat generally goes straight into our energy savings account. Remember it is these very calories stored in the excess body fat that we are trying to get rid of. Unless the glycogen store is depleted there is little chance for body fat to be used up, and very little chance of meaningful weight loss.

In traditional dieting and intermittent fasting, the regular depletion and repletion of glycogen prevents our using the energy bank account (our fat stores) in any meaningful way. In this respect there is likely negligible weight lost and little difference between just eating less and intermittent fasting.

By partially depleting glycogen cyclically there is the distinct possibility that initial impressive weight losses could be masking weight gain due to fat deposition. For example, in the presence of a high fat keto diet, the body will be utilising the food, glycogen and circulating fat first. Basically, anything but the stored body fat unless it needs to. Consuming excessive calories therefore may even compound a weight issue even in the presence of ketosis.

This is not great news for the dieter.

Our brains respond to depleting glucose with a progressively increased intensity promoting the mechanisms of hunger.

Ultimately intermittent fasting is unlikely to sustain a meaningful rate of weight loss and risk dieting failure, not to mention the likely unbearable hunger.

How do we get rid of excess body fat?

Let us go back to our brain, an essential organ for life.

The brain is protected by a membrane known as the blood-brain barrier.  Only certain things in the blood are allowed into the brain. Glucose is, of course, but fat is not.

Starve the brain of energy and we suffer the rapid inevitability of death. With nothing to eat, our castaway will quickly run out of glucose, both from energy cash and the energy current account.

Intermittent fasting is ignorant of the metabolic needs of the human brain

unconscious brain function, uses around 350 calories per day.

One place to go searching for energy would be the vital organs, ie heart, kidney, muscle, etc. Once glycogen is depleted, however, there is little in those organs either. The body, under non-pathological stresses, will do anything to prevent the compromise of its vital organs.

Therefore, to ensure survival, in the absence of glucose the body and most importantly the brain must utilise the body’s savings account, body fat. How else could the human race cope with a famine?

The problem is that there is no mechanism to convert fat to glucose. The only thing possible during a short term fast is to convert some body protein to glucose, a process called gluconeogenesis. This is not what is needed for healthy weight loss yet distinctly possible whilst intermittently fasting as above.

The body has an important metabolic answer. Fat can be converted to ketones. This alternative and completely natural metabolic pathway, promoted in the prolonged absence of adequate sugar levels, is called ketosis.

Ketones, the chemicals produced in the liver when in a dietary ketosis (not to be confused with ketoacidosis), are welcomed into the brain and are happily used by all healthy body cells.

There is no absolute requirement for glucose when in ketosis. The conditions that promote this metabolic pathway can reduce hunger levels. A masterstroke for the dieter, for ketosis in the presence of prolonged calorie restriction allows for comfortable and rapid weight loss.

To lose weight there really must be a calorie intake deficit but not at the detriment to essential nutrition. A total fast will produce ketones, but the absence of any nutrition if long enough can prove fatal.

Just depleting glycogen is a con.

Calorie restriction

Unfortunately, there is a real danger to our health and prospects of healthy weight loss associated with skipping meals and nutrient deficient intermittent fasting like the water fast. These cast a shadow over real and exciting opportunities.

There is mounting evidence that calorie restriction offers impressive health benefits from remission of type 2 diabetes to increasing our longevity.

Ketosis, essential nutrition and very low calorie diets for weight loss.

We have explained that ketosis itself does not produce weight loss.

It is imperative that our essential nutrition is catered for to sustain health. Remember our castaway is not going to benefit in the long run from ketosis, in the absence of essential nutrition.

Nutrient complete, Very Low Calorie Diet (VLCD) formula foods promote the conditions necessary for a stable and continued ketosis and create a calorie gap for a predictable and healthy rapid weight loss.

In shake, soup or bar form, VLCDs contain all the essential nutrition we need but add up to a daily intake of less than 800 calories. The availability and use of cheaper raw materials can have a profound impact on the safety and efficacy of a diet so it is critical to be choosy.

Not all VLCDs are the same.

LIPOTRIM diet - Gold standard diet

Lipotrim, the gold standard of VLCDs, has led the field of healthcare professional weight management for over 30 years. The value of highly trained pharmacist or doctor’s advice and monitoring cannot be underestimated. Lipotrim contains either 417 or 530 calories per day to cover essential nutritional needs (depending upon gender), creating the maximum rate of weight loss whilst delivering the highest quality nutrition.

In fact, understanding the principles behind metabolism etc and by consuming the daily allocation of formulas within a few hours each day, Lipotrim is arguably the ultimate in intermittent fasting.

Intermittent fasting may show great potential for improving our health, even extending our longevity. However, as a tool for weight loss, the ignorance afforded to metabolism, our innate drive to eat and the potential for a lack of complete nutrition makes mainstream intermittent fasts flawed and potentially dangerous. The merits of a controlled nutrient complete fast for weight loss must instead be applauded and not deemed a fad diet.

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