Intermittent Fasting – What & Why?

Intermittent Fasting is a dietary approach which has experienced a resurgence in popularity recently, however it is not a new approach at all. Intermittent Fasting (IF) has been around for centuries with many cultures practicing regular fasting. Its approach is very simple – eat sometimes, don’t eat other times. While most humans do this by default when they sleep every night, extending this period is beneficial for a number of reasons.

Intermittent Fasting


Cardiovascular and Neurological

  • Improved blood pressure
  • Cardiac and brain cells show resistance to ischemic injury
  • Induce similar adaptations to the CV system as does exercise
  • Improvement in HDL, homocysteine and coagulation status
  • Improvements in blood lipids and triglycerides
  • Improvements in TG:HDL ratio, reduction in small dense LDL
  • Neuronal autophagy (autophagy is our body marking cells that are dodgy, or not functioning properly to be broken down and all the good bits of that cell are transported to other parts of the body to be re-used – this is a very good thing!)
  • Mitochondrial autophagy (think of autophagy like the little Pac-Man going around eating all the dysfunctional bits of our cells, leaving all the good bits leftover to be utilised elsewhere!)
  • Brain health via neuronal regeneration
  • Prevention of Alzheimer’s (animal study)

Body Composition

  • Increased fat oxidation (fat burning)
  • Reduction in visceral fat (around your organs) and adipokines (hormones that stimulate fat storage)


  • Increase in growth hormone secretion
  • Improved insulin sensitivity and glucose control

Inflammation and Other Chronic Illness

  • Low carb and IF have been shown to revers T2D and this should be the major focus in the management of the condition
  • Mitochondrial autophagy
  • Beneficial gene expression, important in the longevity and disease prevention (especially cancer)
  • Protective against cancer (animal studies)
  • Anti-ageing (rat studies showing increase in life length)

Immune System

  • Reduced inflammation
  • Attenuation of pro-inflammatory cytokines and immune cells
  • Immune system rejuvenation (rat study)
  • Reduction of old immune cells and regeneration of new immune cells
  • Protection against the toxic effects of chemotherapy in cancer patients

There are many ways to implement IF, the following are some examples:

  • 36 hour fast done 1-2 times per week (or the 5:2 protocol). For example, eat normally on day 1, then skip breakfast, lunch and dinner on day two. The next meal will be breakfast on day 3. This is probably for people who have had experience with IF as you can get quite jittery or shaky if you aren’t fat adapted*
  • 16:8. For example, skip breakfast, then eat lunch and dinner within an 8 hour window. This is quite easy to do every day, it’s easy to manage and it’s a great introduction to IF.
  • 20:4. For example, one meal per day.
  • Alternate day fasting. For example, normal eating on day 1 followed by calorie restricted day (approx. 500 calories) on day 2.

This is by no means an exhaustive list as IF means nothing more than NOT eating for a certain pre determined time, and therefore there are almost limitless variations.

*FAT ADAPTION – is a metabolic adaptation where the mitochondria (energy production centre of all cells) undergo metabolic change, whereby they preferentially utilise fats as an energy source over carbohydrates. There is evidence that shows a period longer than 7days of adherence to low-carb/highfat diet causes metabolic adaptations that substantially enhance the rate of fat oxidation (fancy word for burning fat) during exercise, and to a large extend, compensate for the reduced carbohydrate availability. Compared with finite stores of carbohydrates, fat stores in humans are large (even in someone slim), and represent an almost unlimited source of fuel for skeletal muscle during aerobic exercise.
What the heck does that mean? Our fat reserves are huge in comparison to our glycogen (carbohydrate) reserves. It makes more sense that we would utilise fat over carbohydrate. Remember carbohydrate loading is a relatively new idea coined in the 1960s. Our cells have a huge amount of energy available to them in the form of fat and when we reduce our dietary carbohydrate, it forces them to switch to burning fat.

We can become fat burners, not sugar burners, this means we can eat when we’re truly hungry, which may only be a couple of times per day.
For most people, getting fat adapted means dropping their carbohydrate intake to below 50g per day. To make sure you are on track, you will need to do a few things:

  1. Avoid all processed foods (bread, cakes, biscuits, pastry, muesli/bars, cereal etc.)
  2. Avoid high carb veggies (potentially)
  3. Calculate/track how many of each macronutrient you are getting (don’t worry about calories, just grams)
  4. Keep your protein to 0.8-1.2g per kg of bodyweight
  5. Fill up on fat – think medium chain triglycerides (coconut oil/cream/milk, sheep/goats/cow’s milk products)

Generally fat adaptation happens over 3-4 weeks, you may feel foggy, tired and miserable in the first week or two. It’s important to track your macros to ensure carbohydrate is <50g and increase your fat intake, if necessary. Always drink lots of water, get enough sleep and possibly consider taking a salt tablet ~5g/day to offset the “carb flu.”
Once fat adaptation has occurred, research shows that mitochondria will continue to preferentially use fat as a fuel even when glucose becomes freely available. Don’t sweat the high carb meals on occasion, once fat adaption has occurred, you can’t lose it in one meal.

How do I know if i am fat adapted?

There is only one way you can be 100% sure and that’s to go to a lab and have your breath tested during exercise. Otherwise, the following are clues that you are probably fat adapted:

  • fasting no longer feels like hell
  • exercise after fasting doesn’t make you want to cry
  • you don’t tend to slump in the afternoon
  • you’re less hungry
  • you’re eating less frequently
  • you don’t wake up starving

I naturally came to fasting after adopting a LCHF (low carb, healthy fat) way of eating and finding that i just wasn’t hungry in the mornings – doing some research i discovered that there was no real supporting evidence to the idea that you have to eat breakfast. For me, practicing 16:8 fasting on most days for over 12 months now, i am able to listen to my body and truly understand when i am actually hungry. I used to eat a meal and be hungry about 30mins afterwards, however now i am completely satisfied until my next meal 4, 5, or 6 hours later. The freedom this has provided for me has been absolutely liberating – i no longer stress/think about/freak out about the next meal all the time or having to carry snacks with me in case i get low blood sugar and need to eat right at that second!

By eliminating all the stress and the allowing the natural regulation my hunger hormones, i can trust my body to tell me when to eat – which may only be 1-2 times per day. Intermittent Fasting is one of the easiest health interventions that you can practice, as you can see by the extensive list of health benefits above! It is also cheap, it doesn’t cost you a thing, if anything it will save you money because you will be eating less. I strongly encourage anyone who is looking to improve their eating habits, improve their health, improve their body composition and confidence to give fasting a go!

If you have any questions – i would love to hear from you [email protected]

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