We’ve seen "Intermittent Fasting" appearing in news articles, read about a celebrity trying it, heard it whispered between friends and know of someone’s cousin’s cat who is doing it… but what really is Intermittent Fasting? And does it work?
Put simply, Intermittent Fasting is a cycle of "eating" periods and "fasting" periods - hours or days with little or no food consumption. It is broad term that encompasses various patterns including the 5:2 Diet, the 16:8 Method, Time-Restricted Feeding, Alternate-Day-Modified Fasting and the Eat-Stop-Eat Diet.
Intermittent Fasting methods including the 5:2 Diet and Alternate-Day-Modified Fasting have shown benefits in humans for:
improved cardiovascular health
reduced blood glucose, lipid and insulin levels
increased insulin sensitivity
reduced inflammatory markers
As impressive as these results may be, they have not been shown to be significantly superior to the traditional dieting method of continuous energy restriction. Furthermore, some studies indicate that intermittent fasting patterns are much harder to adhere to and can therefore be unsustainable in the long-term.
“Intermittent Fasting thus represents a valid - albeit apparently not superior - option to continuous energy restriction for weight loss.”
If implemented correctly, Intermittent Fasting can help you reduce your overall calorie intake and promote weight loss. Intermittent Fasting is particularly effective for those individuals who struggle to maintain a reduced calorie intake on a daily basis, or for those who are looking for more flexibility in their calorie intake on weekends.
If you are interested in trialling an Intermittent Fasting approach, Dietitians are perfectly placed to guide you in how to proceed as safely and effectively as possible. A Dietitian can guide you in the most suitable fasting pattern for your unique circumstances, how restrictive fasting periods should be, and what to eat during fasting and non-fasting periods.
Dramatically changing your timing and quantity of food intake to fit within a fasting regime is not likely to bring out the best version of yourself for the first few days. Individuals who begin fasting may notice headaches, hunger cravings, reflux, constipation, poor mood, irritability and report that they are more likely to overeat at mealtimes.
It is important to note that Intermittent Fasting is not suitable or safe for everyone. This approach is not recommended for competitive athletes, those who have poorly managed diabetes, who are chronically unwell, have been recently hospitalised, are pregnant or breastfeeding, or who have (or have previously had) a poor relationship with food. If you are considering trialling a fasting approach, we encourage you discuss it with one of our Accredited Practising Dietitians first.
Seimon et. al. (2015). Do intermittent diets provide physiological benefits over continuous diets for weight loss? A systematic review of clinical trials. Molecular and Cellular Endocrinology. 418(2):153-172.
De Cabo, R. and Mattson, MP. (2019). Effects of intermittent fasting on health, ageing, and disease. New England Journal of Medicine. 381(26):2541-2551.
Collier, R. (2013). Intermittent fasting: the science of going without. Canadian Medical Association Journal. 185(9):E363–E364.