What is the History of Fasting?
Fasting is not a new concept by any means. It is an ancient tradition that has been practiced for centuries by many religions. For example, Ramadan is practiced in the Islamic faith by millions of adult Muslims. Ramadan is a form of intermittent fasting (IF) when no food or drinks are consumed during daylight time for one month.
What is Intermittent Fasting?
IF is an overarching term for cycling between periods of limited food intake on certain days or during certain times of the day, and periods of normal food intake. Simply, you’re cycling between eating and fasting. IF has been receiving attention lately due to potential health benefits including weight loss, blood sugar regulation, and increased brain function.
Why Intermittent Fasting?
Perhaps the most common reason for trying IF is the desire for weight loss. By controlling caloric intake, studies on IF show a decrease in body fat and fat levels in blood, like cholesterol, which may decrease risk of developing chronic diseases such as heart disease.
IF may also help control blood glucose levels in individuals with diabetes; more research is needed to determine impacts on healthy individuals.
Increased brain function (e.g. attention and memory) is another observed benefit. However, it appears to be stronger in people who are obese and overweight.
What are the Different Types of Intermittent Fasting?
- Alternate-Day Fasting
- Alternate between days of normal intake with days where only 1 meal is eaten
- A very extreme approach to fasting
- Whole-Day Fasting
- 1-2 days per week you either:
- do not eat at all or,
- you severely restrict food intake by only consuming up to 25% of your recommended calories (eg. 25% of 2500 calories/day = 625 calories/day)
- A more extreme approach of fasting
- 1-2 days per week you either:
- Time-Restricting Feeding
- Fast for a specific time within the day (eg. 4pm - 8am), and eat normally for the remainder (eg. 8am - 4pm)
- A more flexible approach to fasting. You are likely already doing a shorter version of this as you fast overnight between dinner and breakfast!
Things To Consider
Although there may be some benefit to IF, there are also risks. If you have previously been diagnosed with an eating disorder, feel you have disordered eating patterns, or feel negative emotions (ie. guilt) about eating, you should not engage in IF. Consult a dietitian or health care professional to see what might be right for you.
It is always important to assess your motives for starting IF to avoid falling into a cycle of yo-yo dieting. Almost all diets fail to result in sustained weight loss and can have negative long term consequences on your physical and mental health. The best “diet” is a flexible eating pattern that you enjoy and can stick to for life. More human studies are needed on the long term effects of IF to confirm any benefits. For a summary of IF research, watch this video and see here for additional things to consider before starting.
How to Fast Safely
The most common and safest IF approach is the 16:8, a version of time-restricted feeding. In this approach, you restrict food intake for 16 hours and then have unrestricted food intake for the other 8 hours of the day. Generally, this is done daily but some individuals may choose just to do this on weekdays and have weekends as unrestricted intake.
Some examples of this approach are:
- Eat: 6am - 2pm (8 hours); Fast: 2pm - 6am (16 hours)
- Eat: 11am - 7pm (8 hours); Fast: 7pm - 11am (16 hours)
During a fast it is important to stay hydrated and to be aware of how you are feeling. Individuals may experience hunger, headaches, dizziness, and constipation. If you start to feel unwell or weak, you should break your fast and see your doctor if your symptoms persist.
When breaking a 16-hour fast, do so gradually. Start with a small meal or snack rather than a large meal to avoid a stomach ache or other digestive issues. It is also important to not overeat during “unrestricted eating.” Eat balanced meals as you normally would, being mindful of your hunger cues.
Can anyone start Intermittent Fasting?
- No. Fasting is likely to be harmful for people who are: underweight, pregnant or nursing, have eating disorders and who are under 18 years old.
Can I exercise while fasting?
- Yes, but exercise within reason and using judgement. During longer fasting periods, you may find it more difficult to complete your normal exercises. If this is the case, schedule your exercises to be completed during non-fasting time periods.
- Be sure to hydrate and replenish the electrolytes you’re sweating out. If you’re fasting near and during a competition consult with a physician or sports dietitian.
What can I eat and drink while Intermittent Fasting?
- During the fasting period, it’s especially important to stay hydrated by making water your drink of choice! Water is a great thirst-quencher and is vital for maintaining your health.
- During the eating period, aim to eat a variety of foods at each meal. Include vegetables and fruits, whole grains and protein foods. A balanced meal can help you meet your nutritional needs and keep you feeling good.
Overall, intermittent fasting is not for everyone, or a diet we would recommend long term. If you think IF is right for you, consider starting with a 16:8 regime in a time frame that is best for you. To ensure your health is maintained throughout IF, consider consulting a dietitian for further guidance.
Students living in residence at UBC can speak with the Residence Dietitian. Residents of British Columbia can speak with a dietitian free of charge through 811 or find a dietitian through Dietitians of Canada.