Intermittent fasting — what’s in it for me?
If you had clapped eyes on me a few years ago you would have been looking at an emotionally frazzled, chronically exhausted, comfort eating, hormonal wreck masquerading as Wonder Woman. Cape on, I seamlessly juggled my career, home, husband, dogs, chickens, and kids (in no particular order) whilst finding time to prepare great meals and get to the gym. Just check out my social media, it must be true. Reality was that as soon as I came home and hung up my cape, I resembled a car crash happening in slow motion.
To cut a long story short, I ended up committing to a 30 day nutritional re-boot programme, part of which involved starving myself a day a week, sorry, fasting. I’m sure like anyone else who has dabbled with intermittent fasting, I assumed it was a sneaky way to cut calories. And yes, there is some truth in that — over time people who intermittently fast reduce calorie intake by 20–30% and don’t tend to ‘over feed’ on non-fasting days (in addition to feeling unbearably smug the next day).
But as it turns out, after a few weeks on this new regime, I started to feel a certain clarity, the fog in my head lifted, I felt a little sparkly, I might even go as far as to say I was feeling like myself again. My perspective returned, I stopped being a domestic martyr and wrestled back some me time. My family stopped walking on eggshells around me and started to breathe again.
Intermittent fasting, IF to its close friends, has surely made the leap from obscure fad to the mainstream in terms of health and lifestyle advice over the past few years, but what do we really know about its longterm effects on the mind and body? And could it explain my experience?
IF is defined as the rhythmic disruption to the flow of calories into your metabolism — we need to remember that a calorie is a measure of the energy, not the nutritional, content of our food. Some people practice alternate day fasting (eating less than 500 calories every other day), some people advocate periodic fasting (at least five consecutive days of consuming water or a fasting mimicking diet) but time restricted feeding (eating confined to an eight hour window or less every day) is gaining ground as an eminently less scary way to get all the health benefits and still be able to function in modern life.
Without doubt, our ancestors had a sporadic access to food throughout their lives that depended on their foraging skills and hunting prowess. As a result, over hundreds of thousands of years, our physiology evolved such that our mental and physical performance remained unaffected by fasting. It would seem that hunger is indeed just a feeling, not an emergency!
When you eat a meal, the carbs, fats and proteins are broken down into simpler units by your digestive system and fibre is digested by the bacteria in your gut. These simpler units — the amino acids, glucose, fructose and fatty acids — pass in to your bloodstream and this nutrient rich blood heads off to your liver. Some of the glucose is stored as glycogen and some remains in the blood to be used by muscle and brain cells for energy. Fructose is converted to fat, packaged up and released back into the bloodstream.
Your pancreas senses a high blood sugar concentration (all that glucose) and releases insulin which activates your cells to use up the glucose. Insulin also activates fat cells (adipose tissue) to store the fat. Between meals, glucose and insulin levels drop and fat cells release fatty acids into your blood to be used as an energy source by your cells, in particular, muscle cells. However, these fatty acids cannot cross the blood-brain barrier and so are of no use to your brain cells or neurons. Your liver comes to the rescue, converting fatty acids to ketone bodies which can be used by neurons in the brain as an energy source, as well as operating as vitally important signalling molecules that have a major effect on both cell and organ function.
Approximately 12 hours after eating glucose and glycogen stores are depleted and the body starts to rely on fatty acids and ketones for energy. Your body is now in a fasted state.
And this is when the magic starts to happen. There is reliable evidence from recently published human studies that IF practised over the medium to long term can prevent, and even reverse, all aspects of metabolic syndrome — that includes chronic inflammation, abdominal adioposity, hypertension, cardiovascular disease, diabetes and stroke. Additionally, IF boosts the health of your gut microbiota which can only be good news.
However, it is the incredible benefits for brain health that are even more exciting, and the reason why I remain a convert.
In the fasted state, once the glucose and glycogen has been used up, your cells become stressed which has been proven to cause them to make changes that result in them becoming more resilient, DNA repair is enhanced and they focus on getting their housekeeping done (this is called autophagy). This is important because autophagy is the process by which the 30 trillion cells in our body round up toxins, pathogens, junk protein and damaged organelles — essentially they get round to doing their recycling, clearing out the junk and they end up becoming far more efficient.
Specifically though, your brain is benefitting in a number of other ways. Putting your neurons under stress by disrupting their nutrient supply also leads to significantly elevated levels of BDNF (Brain Derived Neurotrophic Factor) which is responsible for the growth and survival of adult neurons and the regeneration of damaged ones. Studies have shown that a short term IF regimen improved the verbal memory of older adults, and that 2 years of IF resulted in a significant, measurable improvement in working memory. To cap it all, BDNF prevents age related alterations in serotonin and dopamine levels as well.
Giving up eating will literally improve your ability to focus on tasks, learn faster and remember more. You will be happier, sleep better and be in a great mood — that would be the unshakeable smugness you radiate when you break your fast.
IF is more effective at slowing down ageing and disease than the use of supplemental vitamins, minerals and antioxidants (such as vitamins C and E). In fact, the supplementation of vitamins C and E during fasting actually overrides all the benefits of IF — it would seem that cells don’t respond by increasing their natural defences if you help them out and they don’t improve their insulin sensitivity. They need to experience mild stresses to perform at optimal.
One of the most important organelles in your cell are your mitochondria which are essentially your powerhouses. They provide you with energy but one of the byproducts are free radicals. These are highly reactive, destructive little molecules that attack anything and everything, including our DNA and the mitochondria themselves, and the accumulated damage is a primary factor in ageing. And, as you might have already surmised, our neurons have an awful lot of mitochondria because they need to generate a lot of energy which makes them particularly susceptible — we know for a fact that mitochondrial dysfunction is involved in both Parkinson’s and Alzheimer’s.
Our cells naturally produce antioxidants (and they are provided courtesy of a balanced diet) which mop up and neutralise excess free radicals, and the key here is excess. Life is never black and white, and this applies to free radicals. In low to moderate concentrations, free radicals are a useful weapon against invading microbes and play a vital role in cellular communications. However, a natural consequence of ageing is that the free radical damage builds due to producing fewer antioxidants and the decline of our housekeeping systems, amongst other reasons. Evidence suggests that ramping up autophagy through IF targets damaged mitochondria and their new replacements are more efficient, less prone to produce free radicals, and ageing is slowed.
Finally though, the story wouldn’t be complete without briefly visiting the recent news that IF has been shown to completely reverse diabetes in mice and promising results have been seen in human trials — both in terms of an alternate day fasting regime and when a fasting mimicking diet (Diabetes Remission Clinical Trial — DIRECT) was followed for sustained periods of time.
Diabetes is an insulin problem, not a glucose one. Insulin is a hormone that signals to cells to take up glucose from the blood stream by binding to receptors on the surface of the cells, essentially opening the gates. In type 1 diabetes, the immune system mistakenly targets and destroys insulin producing beta-cells in the pancreas. In type 2 diabetes, cells lose their sensitivity to insulin, their insulin receptors stop working, and the pancreas stops producing insulin. Either way, cells are unable to take up glucose and metabolise it to provide energy.
During fasting periods in the mice trials, the pancreas shrunk, autophagy kicked in and damaged beta-cells that were not producing insulin were removed. Remarkably though, after several cycles of fasting and feeding, the beta-cells regenerated, insulin sensitivity improved leading to a significant decrease in blood sugar and nearly normal insulin production resumed. IF had initiated healthy regrowth of the pancreas — it was back in working order.
In the human trials, weight loss was a key factor as diabetes commonly presents in tandem with obesity. In the DIRECT trial, participants lost 10kg on average and 36% essentially reversed their diabetes over 2 years, coming off all drugs. For those who maintained a weight loss of more than 15kg, 70% reversed their diabetes.
Clearly the science holds up, the question is, is IF for you too?
Firstly, it is not just about meal skipping. You need to consider how you are going to break your fast as planning a balanced nutritious meal is imperative. You won’t reap the benefits if you continue to fill yourself up on high calorie, nutritionally bankrupt, processed food. And make sure you drink plenty of water to keep yourself hydrated.
The easiest way to start is probably time restricted feeding — eating from midday to 8pm and then fasting for 16 hours everyday. The key to forming any new habit is to break yourself in gently, after all this is supposed to be a lifelong change and you may feel hungry and irritable for the first month. Reduce your eating window to 10 hours for the first month, 8 hours for the second month and 6 hours for the third month, 5 days a week. The ultimate goal is to restrict eating to a 6 hour window everyday.
If you think the 5:2 approach would suit you better, then aim for a day a week eating 900 (nutrient dense) calories for the first month and 2 days a week for the second month; 2 days a week consuming 750 calories for the third month and then 2 days a week consuming 500 calories is the goal in the fourth month.
Personally, I mix it up, following a time restricted feeding regime some weeks and a couple of times each month I fast for 24–36 hours. This involves having supper on Monday evening, fasting through Tuesday until I break my fast on the Wednesday morning with a fully nutritionally balanced, probiotic shake. During the fasting day I support my body with a botanical based tonic, herbal teas and lots of water. It’s not that scary, honest!
Secondly, be sensible. You shouldn’t be considering fasting if you are pregnant or if you think it might lead you down a path to disordered eating.
And finally, don’t set yourself up to fail! It is much harder to make any sort of lifestyle change if you don’t have the support of your family, so get them on board before you start. There is lots of good advice out there, you are sure to find something that works for you (the Fast 800 Diet by Dr. Michael Mosley is a good place to start, especially is weight loss is also a goal).
