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For thousands of years, animals (including humans) have lived in environments where food has been scarce. Our ancient ancestors could endure long periods of time with very little or no food at all.
So, if it was good enough for those who roamed the earth before us, does this mean ‘going without’ could also be good for our health? With the added pressures on many of us to maintain a healthy weight, is intermittent fasting the revolutionary silver bullet for better wellbeing, or is it the dietary equivalent of returning to the caves?
Intermittent fasting involves cycling between periods of eating and periods of fasting – or going without. While many modern diets are focussed on eating more or less of certain types of foods, intermittent diets focus on when you eat rather than the types of food you eat.
Broadly speaking, intermittent fasting approaches can be divided into three main categories:
1. Alternate-day fasting
This approach involves alternating days throughout the week where no or very few calories are consumed, with days of unrestricted eating. Also known as the “eat-stop-eat” method.
2. Modified fasting regimens
This method involves eating very few calories on certain days of the week, and regular unrestricted eating on the other days. The 5:2 diet falls under this category, where during two days of the week, only 500-600 calories are consumed.
3. Time-restricted feeding
This approach involves adhering to a daily routine where food is only consumed during a certain number of hours in a day. For example, the 16:8 method involves fasting for 16 hours a day and only eating in the remaining eight hours, i.e. between noon and 8pm.
While intermittent fasting seems to be rising as the next new health craze, what does the science actually have to say?
Well honestly, very little.
Now this isn’t to say it isn’t healthy. Science takes time and money, and it is possible that trial results are yet to hit our library shelves. But the majority of scientific studies conducted to date that examine the possible health benefits of intermittent fasting – including reducing Alzheimer’s risk, ageing and cancers – have been conducted either on animals or in petri-dishes. Studies examining health benefits in humans are still quite limited, and until then, the benefits and risks of intermittent fasting are still up for speculation.
While there have been a number of human studies showing weight reduction in people practising intermittent fasting, it’s still not clear which type of intermittent fasting is best for weight loss.
Due to the nature of the diet, intermittent fasting tends to limit the number of calories entering our bodies which can help us to shed excess fat. That said though, studies suggest that intermittent fasting leads to similar weight loss as with traditional calorie-restricted diets. In other words, the weight loss is likely due to eating less, and not eating less at certain times.
An important additional point to note is that the majority of participants in these studies were put under strict, but healthier diets in addition to periods of fasting. For example, participants were assigned a Mediterranean diet rich in fruit and vegetables, olive oil and whole grains. Consuming a Mediterranean-style diet alone can lead to great health benefits and weight loss.
Intermittent fasting combined with a healthy diet may not be any more effective for weight loss than just reducing portion size across three complete meals, or cutting out snack foods. However, some people do find it easier to trial and to stick to – which can be helpful in maintaining a new, healthier way of eating.
Intermittent fasting is not a new practice, but the scientific evidence surrounding its health benefits is still lacking. While intermittent fasting tends to reduce overall caloric intake, it appears not to be any better than traditional calorie-restricted diets. Intermittent diets that don’t also address what we eat may miss a critical part of the food-health puzzle.
The long-term risks surrounding intermittent fasting are still unsettled and intermittent fasting should be avoided if you have certain medical conditions, previous eating disorders or low weight. Individuals who are pregnant or breastfeeding should also avoid these forms of diets.
If you are looking to try this diet, make sure to consult your medical practitioner first. For more healthy eating ideas, check out The Check Up’s dedicated recipes page.
Co-host of the ABC TV series ‘Ask the Doctor’, author of 30 scientific papers and ‘The Doctor’s Diet’ (a cookbook based on science), Dr Sandro Demaio is an Aussie medical doctor and global expert on non-communicable diseases.
For more articles by Dr Sandro Demaio, check out The Check Up’s dedicated section.