With obesity continuing to rise, a popular alternative to counting calories to lose weight has been choosing periods of time to simply not eat.
Harking back to the hunter gatherer days of our ancestors, there were times where food was scarce thus faced with enforced periods of fasting, far removed from our abundance of food in modern society and heavily marketed snacking culture.
Intermittent fasting is not about starving yourself, nor is it about having carte blanche to eat anything in sight when the fast is over. All of these popular regimes work on the premise that the overall amount of food is less over a period of time, but as you don’t exclude food groups such as carbohydrates or fats, there should feel like less deprivation and less need to rely on willpower for long term compliance.
There are a few versions of intermittent fasting in practice extending our usual breaking of the overnight fast to periods in the day, which should naturally reduce your overall calorie intake.
Time restricted eating - eating within a time window such as 12 hours e.g. 7am -7pm or a 8 hour eating window e.g. midday till 8pm and thus a 16 hour fast (16:8). The same timings apply every day, which can help cut down on grazing throughout the day, or eating late in the evening just before bed, when food is unlikely to be burnt off.
Alternate day fasting - every other day eating 25% of calorie needs, and the other day eating normally. There is no universal definition of what this means, so having some understanding of what your calories needs are before you start will help. There is more chance of experiencing hunger trying to keep this up for half of your life, so this method is more likely for short to medium term weight loss goals.
5:2 diet - 2 days a week eating 500 calories and the rest of the days eating normally. This is more sustainable in terms of fitting in with your lifestyle, popularised by Dr Michael Mosley, on the premise that over 7 days, your overall calorie intake will be less.
24 hour fasting - this involves a full fast for 24 hours, a more extreme method so more likely to come with side effects such as tiredness, headaches, mood swings and hunger.
So what are the benefits and risks?
Some scientific studies suggest long term health improvements in markers such as blood pressure, heart rate and cholesterol levels, linking to potential to live longer. They also suggest it supports the immune system, helping the body repair age-related damage and even help prevent cancer. These studies are in their infancy, often small scale or based on animals, so their long term efficacy and safety for everyone cannot be confirmed.
The impact of fasting on our hormones is particularly unclear, in terms of women’s monthly cycles, and our thyroid gland which is the master of our metabolism. So far, men have fared better in fasting trials, and females may struggle with the concept because our hormones are more sensitive to these fluctuations in energy intake.
Anyone susceptible or with a history of eating disorders, fasting clearly may not be suitable. We may associate anorexia with underweight individuals, though it can easily affect those of normal weight. And any issues with blood sugar regulation, fasting is more likely to result in side effects such as hunger, headaches, weakness, and nausea.
On a positive note, our gut lining is thin and sensitive, with rising food sensitivities and irritable bowel syndrome, so giving your gut a 12 hour overnight break at least e.g. avoiding snacking after dinner, will give it more of a chance to repair naturally.
And finally, the main attraction of fasting is simplicity. No counting calories or planning meals, it takes some of the ‘thinking time’ associated with changing our diets. With busy lifestyles, skipping one meal, or reducing calories on busy days may feel a less difficult way to shed some pounds.
Food is complex, not just in the quality and quantity on our plates, but why we eat. It can be easy to follow the herd and try the latest diet craze, or try what your friend has tried, only to find out it didn’t work for you. If there are any underlying health issues, you should always discuss changes to your diet with a health professional as food (or lack of) can have powerful effects in the body.
Fasting has not been around long enough to prove the benefits and risks for everyone, but for some it can complement their lifestyle and be used as an alternative to calorie counting to maintain their weight.
If you would like more information about how food is affecting your lifestyle, please reach out for further advice.