Intermittent fasting is a term used to define various cyclical fasting and non-fasting periods, over a specified window of time. While humans have fasted for most of history, clinical research has more recently focused on the health, body compositional and longevity benefits, and due to the significant results, IF is now taking the world by storm.
The key benefits of IF are:
- Digestive ease – digestion requires a significant amount of energy and the myth that we must “eat every two hours to speed up your metabolism” has caused digestive distress and the redirection of energy away from vital physiological processes. I’m sure you’ve noticed how sleepy you feel after a big meal? Now you know why.
- Fat loss – without the presence of circulating glucose, fatty acid oxidation increases. This promotes fat burning, rather than fat storage, environment. Preliminary research shows us that IF offers comparable weight loss benefits to long term calorie restriction, without the need to count calories!
- Improved sleep – our sleep hormone, melatonin, is highest before bed but negatively impacted by digestion. For optimal sleep, it is beneficial to eat 2-3 hours before bedtime and therefore commence your fasting window earlier (before melatonin is at its highest).
- Breast cancer protection – preliminary research shows us that a 13 hour fast in women could be protective to breast cancer.
- Chronic disease risk reduction – fasting has been should to reduce inflammation and offer protection against cardiovascular disease.
The two main methods of IF are time-restricted feeding or whole-day fasting. There are many versions under each of these umbrella terms, and we explore three of the most well-known below.
The 5:2 Diet
Made popular in 2013 by Michael Mosley, the 5:2 diet involves calorie restriction for two days a week and normal eating for five days. Much criticism followed as the calorie requirements were as low as 500 calories per day for men and 600 calories per day for women. There were also challenges with what could be classed as “normal eating” for the five days per week, with many people choosing quantity over quality and ignoring the significance of nutrient density. In 2018, an updated (and much improved) version, “The Fast 800” was released which offers considerable improvements to the original protocol. The calories have been increased to 800 per day on the two fasting days per week and the nutritional guidelines follow a Mediterranean diet – rich in plant-based foods and healthy fats from nuts, oily fish and olive oil.
The 16:8 protocol is 16 hours of fasting combined with an 8-hour eating window, in one 24-hour period.
16:8 is by far the most protective from a disease risk point of view. Research shows not only breast cancer protection in women but decreased risk factors for cardiovascular disease in both men and women. Logistically it can be more challenging, but prior planning prevents poor performance, as always. A simple example is to eat dinner by 7 pm and break your fast at 11 am. In women of menstrual cycle age, we recommended the inclusion of fats in this fasting ratio, such as a MCT Coffee. This will then not be considered a therapeutic fast but still extremely beneficial for many of the benefits we have discussed.
Your “Fasting Muscle”
While there are many versions of intermittent fasting, before you commence it is important that you should first train your “fasting muscle”. Just like you start with a light weight and progressively increase what you lift at the gym, it is best to start with a small adjustment to your standard eating window, and progress from there. One of the easiest ways to start IF is to simply either delay breakfast, or eat dinner earlier. If you have been habitually eating breakfast as soon as you rise, start planning your eating times to allow for 12 hours between dinner and breakfast the next day. Remember, the definition of breakfast is “breaking the fast”, so while it is still the most important meal of the day, it definitely doesn’t need to be consumed at 7 am on the dot.
After you do break your fast, factors such as your ongoing satiety and exercise recovery will dictate the success of your fast. If you fast for too long for example, you may find that you are needing to graze following your first meal, or you may feel more fatigued in the day or days post-workout. Simply track these parameters as a way to determine when you can safely continue to extend your overnight fast.
From here, you may then experiment with two days of 16:8 per week and continue tracking the above parameters. Many men and post-menopausal women thrive on adding further fasting days, but it is important to consider bio-individuality, especially in females of menstrual cycle age. Much of the current fasting research has been conducted in males and we, therefore, can’t extrapolate the results to everyone. Please also track your menstrual cycle as your IF experimentation continues. A healthy menstrual cycle is a considerable barometer to your overall health and ability to thrive.
There are also a number of situations where fasting isn’t advised at all, such as during periods of high stress and/or adrenal dysfunction; during pregnancy or breastfeeding, or if you are taking certain medications, including insulin. Fasting is also not suitable for children.
By taking a gradual approach, intermittent fasting can be a successful long term strategy to optimize your metabolism body composition and long term health. Please ensure you consume an abundance of plants, sustainable protein and healthy fats and minimize or avoid packaged foods and refined carbohydrates. Fasting should not be an excuse to just “fit your macros” and eat low quality, inflammatory foods. For optimal health and longevity, food quality should always be our number one priority.
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