Written By: Brittani Kolasinski (BHSc Nut, AdvDip Nut Med)
The term ‘Intermittent Fasting’ is broad, vague and very generalised. There are multiple methods of intermittent fasting that have more recently become popularised in the media for its health benefits. A quick Google search of intermittent fasting brings up a list of health claims ranging from improved mental clarity and concentration, weight loss and fat loss, lowered insulin and blood sugar levels, reversal of type 2 diabetes, increased energy, increased growth hormone, lowered cholesterol.
The thing is, although intermittent fasting can provide a number of benefits to your health, bio-individuality needs to be considered and this practice, like many others, must be tailored to suit you as the individual.
What is Intermittent Fasting?
Intermittent fasting involves a period of time during the day or the week where you abstain from foods or calorie-containing drinks. Intermittent fasting has been around for centuries, historically we were hunters and gatherers, food wasn’t as readily available as it is to us now. We wouldn’t wake up in the morning to be met with a fridge full of food, supermarkets down the road or fast food delivered straight to you. Periods of feasting and famine were of the norm, and with this, we were able to progress and evolve. The types of intermittent fasting differ in their time spent feeding and fasting. Some of the most common methods are outlined below:
The 5:2 Diet
Intermittent fasting was first really popularised by Michael Mosely when he wrote the book on the 5:2 diet. What this entailed was eating your normal diet 5 days of the week but only consuming 500 calories on 2 days of the week. These 2 days could be consecutive or randomly throughout the week.
The 16:8, 18:6, 20:4 Diet
This style of fasting restricts food intake to a specific timeframe. It can be anywhere from a 14 hour fast with a 10-hour feeding window, 16-hour fast to an 8-hour window, 20-hour fast to a 4-hour window and so on (you get the drift, right?).
Alternate Day Fasting
This style of fasting is simply eating one day and fasting the next. An intense approach especially when first starting out and one that I wouldn’t recommend without the monitoring of an appropriate health professional.
Fat fasting has been popularised in mainstream media with the beginning of the bulletproof coffee, an idea coined by Dave Asprey which involves consuming calories in the form of fats only and restricting protein and carbohydrates. This style means you still get some of the benefits of fasting but also with the inclusion of calories and energy to the body. When implemented appropriately it can induce a state of ketosis short term which also provides additional benefits.
Time-restricted feeding is similar to intermittent fasting but involves complete avoidance of foods and drink apart from water for a select period of time. Sachin Panda’s approach is focusing on a practice known as ‘Time-Restricted Feeding’ (TRF). This concept is a daily eating pattern where nutrient intake is limited within a window of a few hours, usually less than 12, however, the quality and quantity of nutrient and calorie intake is not changed. He looks into the effects of food and drink intake on the circadian clocks of our organs. We have our master clock that regulates all sleep-wake cycles, but each organ will have their own circadian clock and rhythm that is dictated by food and drink consumption. Anything that your liver will metabolise, even herbal teas that contain no caloric value, will trigger a response by the liver and will, therefore, reset its clock. This means that outside of your allocated feeding window, you are to take in water only. No teas, coffee, juices, none. As these will reset the clock via the effects it will have on the liver.
Fasting Mimicking Diet
Formed by Valter Longo, this style of eating is considered as ‘fasting with food’ so patients are still able to have some form of calorie content but with altering where these calories come from it will trick the body to remain in a fasted state, and therefore increase client compliance in doing so. The diet is primarily a high-fat diet, with low amounts of protein and carbohydrate, giving about 10-50% of their normal caloric intake and participated for about 4 days. The diet is still able to produce effects on some markers of aging and disease states, very much the same as would a water fast for 2-3 days. In studies, fat loss has been observed, most of which was surrounding the organs, known as visceral fat (the type of body fat you don’t want to have) while there was no loss in muscle mass.
How Does Intermittent Fasting Work
Fasting induces a reparative state. A process known as autophagy (‘self-eating’) is the body’s system of spring cleaning, so to speak. Any dead, damaged, diseased or worn-out cells are eaten up, stripped for parts and the end result is molecules that are used for energy and the synthesis of brand new shiny cells, thus improving the overall efficiency of each cell.
“It’s our body’s innate recycling program, autophagy makes us more efficient machines to get rid of faulty parts, stop cancerous growths and stop metabolic dysfunction like obesity and diabetes” – Colin Champ, M.D.
More so with longer term fasts (fasts that are longer than 48hours), stem cells are produced. Stem cells are quite remarkable, they have the ability to become many different cell types, replicating at a rapid rate and may then aid the body’s own healing process by regenerating new cells and ultimately new tissues. Stem cell injections are becoming more of a well-known practice for injuries, although transferring someone else’s stem cells may not be so compatible, the best option is to create them yourself, which you can do through fasting. In mice, periodic fasting promoted a stem cell-dependent regeneration of immune cells.
There are also effects on autoimmunity to take note of, more information on this can be found here
Ketosis is a physiological state that occurs in a fasted state or when following a diet that is limited in carbohydrates, with moderate protein and higher amounts of fat. You see the body has alternate fuel sources, in most cases, the body will utilise glucose from dietary carbohydrates or from glycogen (stored glucose) for fuel, but when this is depleted through fasting, carbohydrate restriction and exercise the body will then switch to ketones that are produced by the breakdown of fats for fuel. Ketones are an excellent source of energy for the brain specifically and add to the cognitive effects that intermittent fasting may have on the brain.
The Benefits on Blood Sugars
The work in this area has prompted the thought that intermittent fasting could be of benefit when addressing blood glucose dysregulation. From the 1950s until today it has been advocated by many to consume 3 large meals and 2 snacks, encouraging foods to be eaten at 3-hour intervals with promises to ‘balance blood sugars’ and ‘speed up your metabolism’. However, now with more recent studies conducted, we can see that food restriction and periods of fasting can be of great benefit in regulating blood sugar fluctuations as well as other metabolic markers. Limiting the amount of food eaten and how regularly you are eating means that there is less glucose present and therefore less insulin needed.
Studies conducted in humans diagnosed with type 2 diabetes assessed the efficacy of intermittent fasting on blood sugar levels. The results concluded that intermittent fasting may reduce blood sugar levels to a healthy, normal range, favoring the implementation of fasting as a safe and effective tool. It makes sense, type 2 diabetes is caused by large amounts of carbohydrates which leads to a flood of insulin in the body that the pancreas just cannot keep up with, so why are they then given insulin to treat it.? Think about it. Why would we give someone insulin to treat a condition that’s caused by too much insulin, to begin with?
Benefits on Gut Health
There are also benefits on the gut. When we have a break from food between meals, and not spending the day picking, snacking and grazing it induces our migrating motor complex. This complex acts as a broom, sweeping away debris and build up from within the intestines. This can only occur during a fasted state and is particularly beneficial with sufferers of SIBO (small intestinal bacterial overgrowth). Please see a medical professional for support in this area, like a Nutritionist (like me, hello) or Naturopath
Fasting has been shown to benefit physical endurance, this I’ve noticed within myself. With periodic fasting overnight, going for a run the following day I’ve found that I am able to run longer, faster and more efficiently. Funnily enough, I was more energetic in a fasted state than if I had eaten food.
Mentally, it’s been noted that when in a fasted state many experience a sense of euphoria. Consider this, without food we should experience better brain function, cognition, and energy. Not the other way around. Our hunter-gatherer ancestors needed to be vigilant and agile when hungry, to be able to hunt and kill to feed again. Now with the health issues, we are facing largely due to the poor diets we are eating coupled with sleep deprivation and stress an onset of symptoms including lightheadedness, irritability, and fatigue commonly occur… Basically the feeling of being ‘hangry’. Not exactly a healthy response.
Intermittent fasting has been shown to enhance cognitive performance, due to its effects on neuroplasticity and synapses in animal studies. Regeneration of myelin sheath, the protective outer layer of our neurons has also been attributed to fasting’s effects, as was observed in the condition of Multiple Sclerosis, an autoimmune condition characterised by the degradation of healthy myelin sheath. It’s also been shown to reduce cancer size by 45%, highlighting the effects that fasting has on disabling the growth of a number of tumours as well as increasing the effects of chemotherapy drugs to target the malignant cells and spare normal healthy cells.
Research has shown that fasting can enhance the effects of chemotherapy. This occurs as the cancer cells become more sensitive to the chemotherapy itself whereas normal healthy cells don’t seem to have the same effect.
In animal models, it’s been shown that intermittent fasting does lead to a longer life. Fruit flies are commonly studied as they have a rather short lifespan, making it easier to note the effects. Results from one study, in particular, found that intermittent fasting (using the 5:2 method for just one month) was sufficient to extend lifespan. It was shown to improve resistance to oxidative stress as well as improved gut barrier function and a reduction in age-related pathologies. Dr. Valtor Longo is really leading the way in this field of longevity and healthy aging and is worth looking into for more information on this topic of fasting and longevity. For the sake of the length of this article, I won’t go into it too much more.
You can read more on his work and the work of Satchin Panda here
Fat and Muscle Mass
During a fast fat is oxidised to provide fuel, this can result in weight loss for most or improved body composition. What’s more is that protein is generally spared, meaning that short term fasts will not lead to muscle breakdown but can actually stimulate the production of human growth hormone that is involved in the synthesis of new tissue, muscle, and even bone.
The Difference Between Men and Women
There is so much information on the benefits of intermittent fasting, however, in the research, there is so much to consider. For example, in women fasting can induce anxiety, insomnia, irregular periods and weight gain. Which is quite the opposite effect than what is claimed by health and wellness advocates everywhere.
Women have a much more sensitive hormonal system, from a biological perspective we want to be fertile and reproduce. So in a state of deprivation, this is shut down. This is how fasting may trigger negative effects for some. Studies have shown that a 2 day fast in women shifted their nervous system state to a more sympathetic dominant one (fight or flight), whereas in men it was the opposite as they were in a parasympathetic state (rest and digest).
More recently the function of hypocretin neurons has gained interest. These have the ability to inhibit sleep and lead to feelings of wakefulness. Their excitation occurs in reaction to the body detecting a starved state. They can act on the female hormonal system and lead to insomnia or trouble sleeping. Male neurons seem to respond to starvation with autophagy far more readily than women, although this is conflicting in the research and more is needed to confirm this effect. Fear not as there are other ways to induce autophagy if this is what you’re after. Exercise and infrared sauna use can also stimulate this effect.
When Not to Fast
If You’re Stressed
Fasting is a stress on the body. When blood sugars dip, cortisol is released to bring blood sugar up to a regular range. Fasting can increase cortisol levels within the blood which can lead to detrimental effects leaving you feeling worse off than before. What can you do? You can practice time-restricted feeding, eating within a 12-hour window and maintaining a 12 hour fast, you will still reap some benefits in terms of cancer risk reduced and longevity benefits without putting too much of a stress on the body.
If You’re Pregnant or Breastfeeding
As we have already noted, fasting elicits a different response in women than it does in men. Pregnant and breastfeeding women should not participate in any form of fasting, restriction of dieting. A nutrient-dense whole foods approach during pregnancy and breastfeeding is crucial, this is a time of rapid growth and development and places huge nutritional demands on the body.
If You Have or Had an Eating Disorder
In no way would I encourage any form of restriction if you’re still working through an eating disorder. Eating regular is important to ensure that your body is nourished and well. I understand how easily information like this can be used to fuel unhealthy habits and encourage more restriction and deprivation.
Hyperthyroidism is a condition where the thyroid is overactive. It involves a dysregulated HPA axis or HPT axis to be more specific. Managing hyperthyroidism requires adrenal support, reducing inflammation and improving sleep quality. Because of the effects on the metabolism regular food intake and antioxidant consumption is needed to maintain body composition and reduce oxidative stress that can occur.
If You Have Irregular or Missed Periods
Hypothalamic amenorrhea occurs when the brain stops communicating with your female reproductive organs because there is too much-perceived stress. This condition is commonly driven by undereating or over-exercising. In this instance, the body will produce stress hormones at the expense of sex hormones estrogen and progesterone.
How To Start
Now, the point to reiterate here is that fasting is practiced intermittently. Not on a regular day-to-day basis. That just takes away the intermittency of it. We don’ know exactly how often, how long or how much people should fast, and of course, know that we are all so uniquely different. Fasting is a stress on the body, and this needs to be considered. When facing high stress in your day to day life, fasting would not be advised for you. I’ve said it before, and I’ll say it again – always consult your health care professional before making any radical changes to your diet and lifestyle and respect their opinions on it.
It you are adamant about starting here is how:
Switch first to a wholefoods diet first – limiting refined sugars, carbohydrates, and packaged foods
Trial cyclical low carb days, eating more fat from whole foods and restricting high carb foods like grains, legumes, potatoes, and fruits.
Trial an intermittent fast for 1 day of the week and note how you feel - listen to your body with this. If you feel worse, then stop.
You may feel some hunger when you first start, but if you start having issues with sleep, feeling sick, light headed and shaking then most certainly honour this and what your body is trying to tell you and stop.
For women do it less frequently on non-consecutive days and on days that you are not doing a high-intensity activity, you can also incorporate more of a fat fast to provide some calories but still getting some of the effects – this can include bulletproof coffees or teas. This will induce ketosis and give you still some cell renewing properties and can provide fuel to the brain.
Please let me know if you do intermittent fasting and how you include it in your life – how has it made you feel? I’d love to know in the comments below!
Yours in health,