Intermittent Fasting 101: Everything You Wanted to Know

Curious about intermittent fasting? Learn how it works, the real benefits, the main methods, and who should take extra care before giving it a gentle try.

Written and medically reviewed by Dr. Courtney Ranieri, ND, a licensed naturopathic doctor registered with the College of Naturopaths of Ontario (Reg. #3726). Last reviewed July 2026.

Intermittent Fasting (IF) has received a lot of hype recently, but it isn't a new concept; it has been practised for thousands of years. Before you can convince me to do anything with the word 'fasting' in it, you'd have to make a good case for it. Here's the thing: you actually fast every single day, we just call it sleeping. From your last snack until breakfast the next morning, you're in a fasted state.

What is Intermittent Fasting?

Intermittent Fasting differs from other diets because it focuses on meal timing rather than what you eat. The idea is that you consciously skip meals to put your body into a fasted state.

A quick biochemistry lesson

When you eat, food is broken down into glucose, which cells turn into energy. This is the fed state, and it relies on insulin to signal that sugar is available. When there's excess glucose, extra insulin is released and extra glucose is stored as fat. Over time this signal can become dysregulated, leading to conditions like diabetes and PCOS. Between meals, in the fasted state, your body relies on stored fat for fuel, turning it into ketones for energy. It takes around 4 hours after a meal to enter this state.

The benefits of Intermittent Fasting

Studies have shown IF can promote weight loss (especially around the belly), regulate insulin, improve appetite control, improve heart health by lowering cholesterol, blood sugar and triglycerides, decrease inflammation, improve leptin control, improve HbA1c, and increase human growth hormone.

The 2 main methods

The 16/8 Method: usually the easiest. Fast for 14 to 16 hours and eat within an 8 to 10 hour window (for example, eat between 10am and 6pm). The 5/2 Method: eat normally 5 days a week and restrict to 20 to 25% of your normal calories on 2 non-consecutive days.

Who may benefit?

Adults who want to lose weight, naturally increase human growth hormone, feel they've lost the ability to feel full, are prediabetic or diabetic, have PCOS or high cholesterol, or want more freedom from food.

An important note for women and anyone with a history of disordered eating: there is evidence that women should be cautious with IF, since it can affect hormones and menstrual cycles. Women should fast on alternate days or a maximum of 3 days per week, and those trying to conceive or with hormonal concerns must be extra careful. If you have a history of disordered eating, this may not be the right approach. Always consult an ND or MD before starting.

Important tips

Make sure you're getting enough fat and protein, don't compensate with extra calories on eating days, and start slow (try a 12-hour fast one day a week and build up). Do not start IF just for fun, if you are under 18, or if you have a history of harmful eating patterns.

This article is for informational purposes only and is not a substitute for medical advice. Always consult your Naturopathic or Primary Doctor before making changes. References available on request.

About the author

Dr. Courtney Ranieri, ND is a board-licensed naturopathic doctor and the founder of Somewhere Health. She earned her Doctor of Naturopathic Medicine at the Canadian College of Naturopathic Medicine in Toronto and holds an Honours Bachelor of Science from the University of Western Ontario. Her clinical focus spans hormonal health, fertility, digestion, and women's health, with advanced training in pelvic floor therapy and integrative fertility care.

Book a visit with Dr. Courtney