Welcome to Ask A Dietitian, a series where Yahoo Canada digs into food trends and popular nutrition questions with registered dietitian Abbey Sharp.
This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. Contact a qualified medical professional before engaging in any physical activity, or making any changes to your diet, medication or lifestyle.
Among many viral diets and weight loss hacks, one trend is becoming increasingly popular: intermittent fasting.
There are dozens of ways to do it, and many wellness influencers swear by it for its alleged health benefits and weight loss results.
One TikTok user identified as Emma, (@yourfastingcoach) claimed in a video she lost 40 pounds in one year without working out, and claims the top reason was due to intermittent fasting.
"I can't stress this enough, intermittent fasting is gonna melt your fat off," Emma claimed in the viral TikTok.
But how much of that is true? To find out, Yahoo Canada spoke with registered dietitian Abbey Sharp.
What is intermittent fasting?
Intermittent fasting is an eating pattern that involves abstaining from caloric foods or beverages for a designated amount of time.
According to Sharp, there are different ways to do it.
"For some people, it just means not eating in the middle of the night, and for some people that means not eating for a whole day," she explained.
These are the most popular fasting methods:
Alternate-day fasting means alternating between feeding days and fasting days in a week. For example, eating normally on Mondays and then fasting on Tuesdays.
The 5-2 fasting method involves eating normally five days a week, and then fasting for two days or eating minimal calories for two days.
The 16-8 method is also known as the restrictive fasting method. It involves fasting for 16 hours (overnight and skipping breakfast), and eating during an eight-hour window (lunch, snacks and dinner). It's currently the most popular fasting trend.
Does fasting help with weight loss?
Dietitian Sharp says though people can lose weight on an intermittent fasting program, there are a lot of misconceptions.
"Intermittent fasting has a lot less to do with the body using body fat for energy, or keeping insulin levels suppressed, and it's more just to do with the fact that we're skipping a meal."
Sharp explained research has shown most people won't make up for all of the calories they missed when they skip that first meal.
It's not magic, it's just a calorie deficit.Abbey Sharp
"When comparing intermittent fasting diets to calorie counting, or just maintaining a caloric deficit spaced out throughout the day, people tend to lose weight at the same rate," Sharp said.
"For some people, it's easier to be in a calorie deficit when you just mindfully skip the whole meal, rather than chiseling away at calories at each meal and snack."
Are there health benefits to intermittent fasting?
Weight loss aside, Sharp claims there are health benefits to fasting — in moderation.
The most common benefit to this eating pattern is reducing blood sugar and insulin levels, which can benefit anyone.
"Having more stable blood sugar levels can help with not having those those crashes in the day," Sharp said.
"But it's particularly of interest to folks with Type 2 diabetes, and pre-diabetes, who are looking to get their A1Cs, their fasting glucose levels, under control."
Sharp said fasting also may "help with lowering inflammation and oxidative stress in the body, which could potentially play a role in reducing the risk of various other chronic diseases."
With longer fasts, a "big" benefit that's often seen is autophagy, also known as cellular repair.
"The body's essentially self-eating its sick or damaged cellular matter, which then gets replaced with newer, healthier cellular matter," Sharp explained.
Another important benefit, specifically to those with digestion issues, is giving the body enough time to fully complete "as many rounds" of the migratory motor complex — a natural detox mechanism.
This usually occurs during overnight fasts (12 to 14 hours).
Essentially, it's "a sweeping broom in our gut that helps to move all the matter through our digestive system," Sharp explained. The mechanism moves particles of food and results in pooping.
Anytime we have a bite of food, it halts the migratory motor complex.Abbey Sharp
"Some people just need more waves than others in order to maintain good regularity and good gut function," she added.
"If we're snacking late at night, and then waking up and having another snack, and we're kind of always like having these little bites; anytime we have a bite of food, it halts the migratory motor complex, and it has to start that wave all over again."
Are there risks to intermittent fasting?
According to Sharp, while there are safe ways to reap the benefits of fasting, extreme fasting should never be done without medical supervision.
And for some people, those with a high metabolism, the risks of a strict eating pattern can outweigh the benefits.
"They just need more meals and snacks in the day... they have high metabolic needs, high caloric needs, they may have goals, for example, they're trying to build muscle... And for them, fasting is not going to be healthy."
A lot of online content and advice around fasting is "incredibly dangerous," and "sends the wrong message" to young people, she added.
"[It] is promoting and perpetuating this idea that we should be ignoring our hunger cues — that that is somehow an act of self care or self control that we should be proud of," Sharp said.
A lot of people on social media take it way, way, way too far.Abbey Sharp
"I've seen people promoting water fasts up to 25 days... I think it's incredibly dangerous to promote something as extreme as not eating for an entire month," she claimed.
"I also think it essentially casts snacking, or even eating, in a negative light."
Fasting and intuitive eating
The expert's advice? Fasting "doesn't need to be all or nothing."
Sharp said "regardless of how many potential health benefits it may have," she does not recommend creating arbitrary rules, for example, not eating until noon.
"It's very likely to do more harm than good in the sense that it may conjure up all sorts of obsessive thinking about food," she explained.
Sharp advises, if you wanted to give fasting a try, incorporate it into your day "as intuitively as possible."
"This is where gentle nutrition really comes in, which is an important tenet of intuitive eating."
For those who wake up hungry, she advises adding more fats and more protein to you dinner.
Snacks need to be "not just a handful of chips," but maybe adding some nut butter or yogurt into the mix too.
Those who are "not so ravenous" when they get to their next meal, "they can make more mindful decisions about what to eat."
And, Sharp advised, "be aware of the content that you're consuming around fasting."