Fasting is nothing new—ancient fasting records have been recorded as early as 1500 BC but recently it’s become one of the most talked about wellness trends. There are podcasts devoted to it, NYT best selling books on the topic, and everyone from Halle Berry, Jennifer Aniston, Hugh Jackman, Reese Witherspoon, Tom Brady, and even Elon Musk have all raved about the benefits of intermittent fasting. But does it have some real science-backed benefits? Read on to find out if skipping your breakfast is worth it.
What actually is intermittent fasting?
Intermittent fasting is an eating pattern that cycles between periods of fasting and eating. The most common fasting schedules are the 16:8 method and the 5:2 method.
16:8 method: This schedule is 16 hours of fasting followed by eight hours of eating. With this diet you’ll eat your meals and snacks within an 8-hour period of the day. This might mean eating between 12 pm and 8 pm (skipping breakfast) or between 9 am and 5 pm (having your last meal early in the day). While fasting you avoid solid food but you can drink fluids.
The 5:2 method: On this schedule you will have 2 non-consecutive days on a low-calorie intake, usually aiming for around 500-600 calories. The other 5 days of the week you eat normally, without restrictions. The 5:2 method was made popular by The 5:2 Diet by Kate Harrison.
Other methods involve different fasting windows such as 12 hours of fasting and 12 hours of eating and alternate-day fasts, where you eat approximately 30% of your regular calorie intake on fasting days.
How will it impact your weight?
A 2015 study examined 40 studies and found that intermittent fasting was effective for weight loss, with a typical loss of 7-11 pounds over 10 weeks. However, a 2017 study that followed 100 clinically obese individuals for one year did not find intermittent fasting to be more effective than daily calorie restriction.
Most recently, a 2022 study published in the New England Journal of Medicine followed 139 clinically obese individuals for one year and concluded that intermittent fasting is not more beneficial than calorie reduction without a restricted eating time. The results led the author, Dr. Ethan Weiss, a diet researcher at the University of California, San Francisco to give up intermittent fasting after practicing it for seven years. “I started eating breakfast … My family says I am a lot nicer.”
Many scientists studying intermittent fasting would like to see larger studies done. What we do know is that if you don’t like calorie counting, intermittent fasting might be useful for weight loss.
Is it safe for your heart?
New research published this year followed the eating patterns of 20,000 American adults for eight years. The study found that 414 of the participants who limited their eating to eight hours in a day had a 91 percent greater chance of dying from cardiovascular disease than those who ate over a 12 to 16-hour time frame.
The researchers had expected to see the opposite. However, the author of the study, epidemiologist, Dr Zhong noted that participants who were intermittent fasting tended to be younger, less educated, lower income, and more likely to smoke.
Dr. Zhong cautioned that more research needs to be done but, “Based on the evidence as of now, focusing on what people eat appears to be more important than focusing on the time when they eat.”
Are there any other proven health benefits?
The studies on the health benefits of intermittent fasting are mainly on animals or involve very small samples of human participants. But here are some interesting recent studies!
Aging
A 2019 study on mice showed that intermittent fasting helped delay various conditions common in aging mice. This has yet to be studied in humans.
Cell Repair
A 2023 study on 75 young males found intermittent fasting helped to activate autophagy. This is the body’s way of cleaning out damaged cells so it can regenerate newer, healthier cells. This could help prevent cancer and Alzheimer’s disease.
Inflammation
A 2019 study of 12 healthy normal-weight participants found that fasting improves chronic inflammatory diseases.
Brain Health
A 2020 study of mice showed intermittent fasting significantly preconditions the brain against post-stroke damage and improves the long-term functional outcome.
Advice for beginner fasters
Dr. Mark Mattson, a neuroscientist at the National Institute on Aging and Johns Hopkins University School of Medicine advises:
- Eat whole grains, healthy fats and protein, and limit saturated fats.
- Avoid sugar and refined carbohydrates.
- On fasting days, be sure to stay well-hydrated.
- Over four months, gradually decrease the hours and days of restricted eating and the amount of calories consumed on fasting days.
Be mindful to make sure you are getting enough protein! In the 2022 study, participants lost muscle because their overall protein intake dropped.
Keep a journal of how you are feeling on the days you fast. 38% of people dropped out of 2017 study, intermittent fasting isn’t everyone’s cup of tea! If you feel restricted or it makes you feel unhappy, then intermittent fasting just might not be for you.
Consult your healthcare provider. For most people, intermittent fasting is a safe diet to try. But it’s good practice to consult your healthcare provider and ensure you have no underlying issues that might make it unsuitable. There are some people who intermittent fasting is not suitable for including those under age 18, women who are pregnant or breastfeeding, people with type 1 diabetes who take insulin, and people who have a history of eating disorders.
