Intermittent fasting guidelines

How to do an intermittent fast

The good news is that Intermittent fasting guidelines are the same for all lengths of intermittent fasting. So if you’re planning a fast of 16 hours with an 8-hour window for eating, a 12-hour fast or a more ambitious 24-hour fast, the advice on how to best achieve this, while minimizing any unpleasant side effects,  is going to be the same too.

Intermittent fasting (IF) refers to any period of time up to 3-5 days during which you voluntarily stop eating. A longer fast is not IF, it’s starving and its not good for you at all.

What happens when you fast?

People normally become interested in the idea of starting a short fast because of the growing amount of evidence that suggests that when you eat is more important than what you eat. There are various ways of intermittent fasting with some people choosing to go on a short fast once or twice a week.  The 16 hour and 24 hour fasts being the most popular choices. Others prefer a 24 hour fast on one or two days each week.

One of the main reasons for choosing to fast is that even a short fast has a big effect on insulin levels, and lower levels of insulin make it easier for your body to metabolize your fat stores. Insulin sensitivity also improves, reducing your chances of developing a number of health conditions, most commonly type two diabetes and cardiovascular disease. Other benefits include weight loss, improved cognitive function and even longevity.

Levels of Human Growth Hormone (HGH) increase dramatically during a fast and there are many health benefits which lead on from this. HGH also improves weight loss, plus higher levels improve bone density, muscle loss and loose skin.

When insulin levels are high, HGH is low so it’s easy to see why these two facts about intermittent fasting – it’s ability to lower insulin and increase HGH – work together to bring many of the amazing health benefits. There are other methods of increasing HGH but here we are concentrating on bringing the benefits via fasting.

It’s no surprise that intermittent fasting is becoming so popular especially with those aged over 40 as HGH levels naturally reduce as we age. People are often looking for ways to become healthier and live longer and so fasting is being taken up as a life style in ever growing numbers.

When eating a keto diet, intermittent fasting can take the benefits of being in ketosis to a whole new level. Combined, there is even better weight loss and health benefits than just practicing one without the other.

Is it healthy to miss a few meals?

It is perfectly healthy to skip a meal or two. You will not die if you miss breakfast, and it’s a great strategy if you plan on a 16/8 fast. You could begin the fast after your evening meal at about 8pm, miss breakfast and enjoy lunch at 12 noon the following day. This way you will have fasted for 16 hours, and sleep time does count! If you’re wanting to, then pushing lunch to 2pm would achieve an 18/6 fast with very little extra effort.

Despite what you may have heard, this way of eating does not lower your metabolic rate. Some studies have shown that it may actually increase your metabolism. Only during a long term fast would your metabolic rate be reduced, as your body seeks to stay alive by minimizing its energy requirements. A long term fast is a completely different thing to intermittent fasting, and is recognized by the body as a state of starvation.

Equally, there are many studies that seem to show that intermittent fasting is more beneficial for weight loss than calorie restriction, which does lower your metabolic rate. This is why people so often gain back all their lost weight after reducing their calories. IF saves this from happening to you.

Due to the fact that a fast is a stress on your body -albeit a welcome one – your body will increase production of norepinephrine. Norepinephrine is one of the chemicals involved in the flight or flight response to danger, and one of the effects of norepinephrine is that it causes the fat cells to release fatty acids in order for you to have more fuel to burn. Again, this is good news if you want to lose weight.

Autophagy and intermittent fasting

However, one of the top benefits of IF is autophagy. This is a massively beneficial process for your body, and autophagy makes IF worthy of doing all on it’s own. This subject requires a few pages alone and you can read more about it by visiting  Autophagy and fasting  but I’ll briefly describe it here:

After a fast, even a short term fast, your body begins a process of autophagy. A fast of 12 -24 hours seems to be best for this, but any fast over 12 hours would be good. Autophagy begins when the body registers a complete lack of food. As a survival technique, your body begins to utilize any damaged cells for energy, and to clean out old cells and misfolded proteins. This includes any senescent cells in your tissues. This clean out of old or damaged cells is very important because they cause inflammation which has been implicated in the development of many diseases.

There is evidence that autophagy reduces the incidence of cancer, diabetes, liver disease and autoimmune disease. It also has a great anti aging effect, improving the appearance of loose skin, improving memory and lifting your mood.

Cognitive function overall can improve, as autophagy clears damaged cells in your brain. This has many implications for the prevention of Alzheimers disease and other neurodegenerative conditions. Autophagy  enables the regeneration of all cells including  brain cells.

Due to the elimination of pathogens in the body, the immune system is also reset after a period of autophagy.


There is evidence that combining exercise with IF helps to maintain lean muscle mass. If you weight train,  working out 3 times a week in the gym will prevent any muscle loss as well as strengthening your bones. However, if you want to increase muscle mass, you will have to make sure you are consuming enough in the times you can eat. It’s all too easy to under eat when the food you’re consuming is high fat and can leave you feeling full for a long time.

Personally, I weight train in a fasted state but only because I don’t like the feeling of food in my stomach while I’m training. With regard to weight loss, there is no evidence to say that training fasted has any benefits over training after a meal. However, there is evidence that IF reduces the performance of serious gym dwellers and professional athletes.

So unless you’re a world-class athlete, it’s probably down to personal choice.

Both aerobic exercise and weight training can reduce appetite for one to two hours afterwards, so combining exercise with your IF regime is going to benefit you in more ways than one.

Should you practice intermittent fasting?

With the keto diet, exercise and intermittent fasting all leading to autophagy, it’s clear to see that having these three things in your life is going to be hugely beneficial.

There really isn’t anything bad to say about the effects of intermittent fasting on your body. To be fair, more research is needed on the link between metabolism and intermittent fasting, but the science already available suggests that IF is better at protecting lean muscle than lowering of calories.

Make it easier for yourself

So whether you choose one of the time restricted eating plans, or go for alternate day fasting, there are some things that you can do which will make this a lot easier on yourself.

In my opinion it’s important to have a clear goal for your fasting. Are you trying to lose weight or improve your health? Keep your goals clear and in mind as you begin your fast. Don’t beat yourself up if you fall short by an hour or two on your first attempt. IF definitely gets easier the more you do it. You will be more fat adapted each time, so more able to use your own fat stores for energy, which will prevent you feeling hungry. This normally takes a little practice.

Remember that even a short fast has benefits, there is no need to aim for 24 hours with your first attempt.

Some pink Himalayan salt in water will help balance your electrolytes. This is especially useful if you have a headache or muscle cramps. Green tea can help to lower hunger, and is a great anti inflammatory too.

I have noticed that some people are suggesting that you can drink fruit juice on a fast. Fruit juice is high in sugar and if you’re drinking it you’re not actually fasting. Any amount of food will stop autophagy dead, and you will loose the benefits of IF.

I believe that for IF to have all the health benefits you should drink only water, tea or black coffee.

I find IF very much easier if I keep very busy. It takes my mind off the fact I’m not eating. Any hunger I do feel doesn’t worry me as I know that it’s a feeling that passes very quickly, especially if I focus on something else.

It also helps if your final meal was low carb, and if you were already in ketosis then so much the better. This makes the fasting period very much more doable.

Just keep in mind your goals, and all the benefits. Keep moving and look forward to a healthier you at the end of your fast.

Intermittent fasting is not difficult, and any short term pain is definitely worth the long term benefits.

If you’re doing an 18/6, 16/8 or even just a 12/12 fast, your body will thank you. Do this a  couple of times a week, or even every day depending on how you feel. If you’re doing a 24-hour fast, then once or twice a week would be enough.

For longer fasts of up to three days,  probably every 4 months or so would be sufficient.

I don’t recommend any fast that is longer than 3 days, and there is zero evidence that any of the benefits are increased by a fast of longer than this. The goal is weight loss and/or a new, healthier you. This can all be achieved with IF that doesn’t extend beyond three days.

Don’t stress, do what you can and know that it gets easier each time you try it. Always start with a shorter fast. You can prolong it if you’re wanting to when you get to the end and still feel good.

When ending your fast there are differing opinions as to what you should eat for your first meal. Some say that you should take a small meal and wait for a while before eating something more substantial.

Personally I have never had a problem with  breaking my fast with a normal meal. I’m pretty sure that when our ancestors caught a meal after a few days of going hungry, they wouln’t have worried about how best to end their fast; they would have eaten all they could.

This is probably something that you will have to work out for yourself. Go with whatever makes you feel good.

Your body with thank you for your efforts.

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