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Intermittent Fasting (IF) is a diet that has experienced a tremendous boom in popularity over the last two decades. It is characterized by periods of fasting when no energy is consumed. There are many ways to practice IF however all require at least twelve hours of fasting. The main philosophy behind the diet is to mimic the feeding times of human ancestors, when the average human would not have constant access to food. Intermittent fasting can be practiced multiple ways and for many different reasons such as overall health maintenance, improvement of diet related diseases, weight management, and religion. But does it work?


Weight Management and Fat Loss

Short answer: probably not. Long answer: some studies have reported that following an Intermittent Fasting diet could help obese people lose weight meanwhile others report no significant link between fasting and weight loss. In theory, fasting would allow adequate time for the body to use its short term energy supply stored in the liver and move onto burning fat stores for energy which would then result in fat loss. In practice IF has not been observed to be any better for weight and fat loss over eating a healthy, balanced diet. Some people do see results however those could be attributed to storing less water weight and paying more attention to diet. Obsessing over eating times and assigning food morality (whether something is “good” or “bad”) is a counterproductive and stressful mindset. As with any diet, it is important to practice mindfulness and to not push your body past what it is capable of doing. 


Diet Related Diseases

It is important to acknowledge that there is a lack of high quality long term studies focusing on Intermittent Fasting and that most of the existing ones study IF’s effects on obese people. This means that there is still mixed evidence and that the results of one specific population can not be generalized onto other populations. There is more substantial evidence that fasting could potentially improve insulin and leptin sensitivity in the body. Insulin and leptin are both naturally occurring hormones that help regulate how your body uses energy, stores fat, and responds to the different components in food such as sugars. Diet related diseases which can be attributed to insulin and leptin disorders include obesity, diabetes, hypertension, and kidney disease. Improving insulin and leptin sensitivity could potentially prevent or slow down these diseases.

Every time calories are consumed the body reacts to the nutrients. Continuous eating spread over the day produces many spikes in insulin and leptin. The body gets used to always being fed so in turn it produces a constant level of these hormones. Fasting allows for rest so that the body does not always have to pump these things out and eventually gets less used to them and therefore increases sensitivity. 

To give an analogy, imagine eating ice cream every single day. Eventually you would stop being as sensitive to its taste and think of it as your daily routine instead of something novel. Now imagine eating ice cream only once a month: the treat now becomes more special and you are sensitive to it’s flavour since it is something you do not always have! This is similar to what happens in the body with insulin and leptin.


Bottom Line

Intermittent Fasting is currently not endorsed by any credible Canadian nutrition association. It is not an alternative to the good ol’ healthy and balanced diet however it could potentially increase sensitivity to certain hormones and could slow down diet related diseases.