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Intermittent Fasting 101

By Iris Lozano, RD on October 23 2018 | Nutrition & Recipes

What is intermittent fasting? 

Intermittent fasting is a type of eating pattern that focuses on alternating periods of eating and fasting, sometimes accompanied by an overall calorie restriction during eating periods. During fasting periods, no food is eaten; however water, black coffee, tea, and other non-caloric beverages are consumed.


What are the different types of popular intermittent fasting programs?

  • The "8/16 Method": This method involves daily fasting for 14-16 hours with an eating window of 8-10 hours. Most people achieve this by skipping or delaying breakfast. This is known to be the most popular method of fasting today.
  • Early time-restricted feeding: Planning for a 6-8 hour eating window early in the day to optimize food metabolism rhythms, followed by a 16-18 hour fasting period. For example, for someone following this program, an eating window may be from 7am to 3pm and one would fast from 3pm until 7am the next day.
  • The 5:2 method: This method involves maintaining a normal eating pattern for 5 days of the week and then fasting for 2 non-consecutive days. On fasting days, some food is still consumed - men typically aim for 600 calories and women, 500 calories.
  • The eat-stop-eat method: Individuals follow a 24 hour fast 1-2 times per week. This can be achieved by starting to fast after dinner one night and not eating until dinner the next day.
  • Alternate-day fasting: As the name implies, individuals engage in fasting every other day by having approximately 500 calories worth of food on fasting days.
  • The warrior diet: This approach involves fasting or only eating small amounts of whole raw fruits and vegetables during the day and then having one complete meal at night.


What are the potential benefits and risks of intermittent fasting?

Potential Benefits: 

  • Weight loss related to caloric restriction fasting patterns (when combined with regular exercise) may be achieved.
  • Some report improved sleep quality and satiety when eating windows occur earlier in the day vs later in the day
  • Potential to reduce night time eating/cravings for food during the evening 
  • Potential to reduce blood glucose and improve insulin sensitivity

Potential Risks:

  • Difficult to maintain large fasting windows
  • Decrease in energy during fasting periods & reduced motivation to engage in physical activity 
  • Increased likelihood of binge eating when fasting periods end
  • Potential for nutrient deficiency and muscle loss due to overall decreased intake of nutrient-rich foods 
  • Headaches, fainting, weakness, hunger pangs or other symptoms 
  • May regain weight after fasting period (potential impacts on metabolic system)

I'm considering intermittent fasting, is there anything I should know?

Intermittent fasting isn't for everyone and for certain individuals, this type of approach to eating poses significant health risks. Before considering intermittent fasting, it's important to seek the advice of your doctor and to work with a registered dietitian. 

Intermittent fasting is NOT recommended for those with increased nutritional needs, those with specific health conditions or certain health risk factors, or those requiring consistent meals throughout the day. For example, intermittent fasting is NOT recommended for those who are:

  • Underweight
  • Below the age of 18
  • Pregnant or nursing
  • Recovering from surgery
  • Individuals with Type I or Type II Diabetes
  • Individuals with hypoglycemia
  • Individuals with a history of eating disorders or disordered eating
  • Individuals taking certain medications such as those that must be taken with food - if you fall into this category, speak with your doctor before considering restricted eating patterns 


My doctor and my dietitian have determined that, based on my health status and health history, intermittent fasting is safe for me. Any tips for someone starting out?

  • Remember to stay hydrated during fasting periods. Need help? Try our hydration challenge
  • Keep in mind your work, social and physical activity schedule and assess if intermittent fasting will impact your behaviour and performance or negatively impact how much physical activity you engage in. 
  • Focus on healthy, nutrient-dense, balanced meals during "eating windows"
  • Consult a registered dietitian to ensure that your micronutrient, multivitamin, and protein needs are being met. Your dietitian might recommend supplementation. Consult your doctor and your dietitian before starting any form of supplementation. 
  • Pack healthy snacks on fasting days in case you do get hungry and want to stop fasting for a period of time


What does a typical day look like for someone following the "8/16 Method" of fasting?

7 am-11 am: Water, black coffee or tea without sugar or milk 

11 am-12 pm: A typical, healthy, dietitian-approved breakfast or lunch meal. Examples include:

  • Smoothie made with ½ cup whole fresh or frozen fruit, 1 tbsp natural nut butter, 1 tbsp ground flax seeds, 1 cup of baby spinach or ½ cup cooked cauliflower or cooked zuchinni, and a plant-based milk or 2% dairy milk as liquid base.
  • 1 cup cooked whole oats + 2 tbsp hemp hearts + 1 tbsp chia seeds + ½ cup blueberries
  • Sandwich on whole grain bread with 40g cheese + handful sprouts + ½ cup baby kale or spinach + ½ avocado
Download the recipe booklet

2-3 pm: Healthy snack (if hungry)

  • Example: ¼ cup nuts (almonds, pistachios, cashews, etc.) + medium apple or an orange

5 pm-7 pm: Balanced dinner

  • Build dinners using "the plate method" (fill up 1/2 your plate with vegetables, 1/4 with healthy carbohydrates such as fruit, legumes, and whole grains, and fill up the remaining 1/4 with healthy proteins) 
  • Include fish 2 times per week
  • Include healthy fats, nuts, and seeds 

8 pm onwards:

  • Only caffeine-free/herbal teas, water, mineral water


Questions? Click on the button below to speak with a registered dietitian at Medisys.