8 Intermittent Fasting Myths To Stop Believing Immediately, According To A Dietitian

An expert explains.

Despite being one of the most popular diets in recent years, intermittent fasting is still widely misunderstood.

In fact, intermittent fasting is different to most diets, as it doesn’t dictate what you should eat, but rather when you should eat. 

And research has found that intermittent fasting is effective for weight loss, partly due to calorie restriction (eating less energy than you use).

But even though it’s become more accepted in recent years, and has been promoted by a number of celebrities, including Jennifer Aniston, Chris Hemsworth and Halle Berry, there are still many myths circulating about the diet.

So, to help break them down and clarify if, how and when intermittent fasting actually works, we consulted Accredited Practising Dietitian Chloe McLeod to bust some of the most popular myths out there.

1. Intermittent Fasting Means You ‘Just Skip Breakfast’

“This is a myth. Whilst most people will fast from 8pm to midday the following day, this isn’t a hard and fast rule,” McLeod explains to marie claire.

“You can break your fast anytime you like. [You can] tailor your times to suit you, maybe eating from 7am until 3pm. If this suits your lifestyle better than starting to eat later in the day, that would be encouraged.”

fact, a scientific analysis from 2023 noted that intermittent fasting has religious origins, such as Ramadan, where Muslims fast during daylight hours. By that logic, someone would skip breakfast and lunch, eating only at dinner and in the time before bed.

“I think this has been misconstrued due to so many people skipping breakfast and starting to eat at lunchtime as their means of fasting. Also on the 5:2 [intermittent fasting diet], this is not about certain times in the day, and breakfast is commonly included,” McLeod says.

2. Breakfast Is The Most Important Meal Of The Day

The idea that breakfast is your most important meal is a frequently espouse one, and often confuses people when it comes to intermittent fasting and the idea of eating later than the traditional breakfast window of time. The final verdict?

“It’s another myth,” McLeod tells marie claire. 

“For some people, it is an important meal as they wake up hungry, or train in the morning, so they require breakfast to refuel.

“If you train in the morning and skip breakfast, this may result in being more I’m hungry later in the day. That said, Some people do find they feel better starting eating later in the day, which is usually due to time that works with their lifestyle.”

(Credit: Getty)

3. Intermittent Fasting Puts You Into ‘Starvation Mode’

Another common question about intermittent fasting is whether it puts you into ‘starvation mode’. But, as McLeod explains, this is “another myth”.

“Research has shown that fasting for short periods can have beneficial impact in some people,” she says.

“However, by taking so long to eat again, this may leave you feeling starving, which may end up resulting over eating.”

In fact, it’s quite likely that people who make this claim have misunderstood the research, McLeod emphasises.

“The other place research may be misconstrued is due to the thermic effect of food. This is the energy it takes your body to digest what you’ve eaten. Eating regularly increases this effect, so technically increases your metabolic rate,” she says.

“However, if by eating more regularly you are eating more food, this positive impact is negated if the goal is weight loss or maintenance, as it is easy to eat more calories than the thermic effect of food burns.  Regardless, fasting for 12 or 16 hours won’t cause your metabolism to slow more than its usual rate.”

4. You Will Definitely Lose Weight With Intermittent Fasting

While there are a variety of reasons people choose to do intermittent fasting, the goal of weight loss is a common one. But simply changing the window of time in which you eat does not necessarily lead to weight loss.

“It’s likely, but not definite,” McLeod says. “What you eat still plays a massive impact. If you fast but are living on poor quality food, you may find weight loss doesn’t occur.”

“Also, for some with other health conditions, fasting may impact ability to lose weight. I think the belief of ‘definite weight loss’ has come from some very noisy voices in the media.”

Selena Gomez eating pasta.
(Credit: @selenagomez)

5. You Can Eat Whatever You Want In Your Fasting Window

“Making great nutrition choices is essential, regardless of the style of diet you follow. If you choose high salt, sugar and saturated fat foods, regardless of your weight or fasting, this won’t result in a healthy body,” McLeod explains.

This is backed up by a comprehensive analysis of intermittent fasting research, which noted: “To preserve lean body mass, a protein-rich diet and accompanying resistance training are recommended”.

“This myth may have come about as the amount of food you eat in the eating window, is same as what you’d usually eat across the day, so it can feel like a lot of food, with some finding it easy to overdo,” McLeod says.

“Because of this, it may feel easier to eat more energy dense options, like burgers and fries, even though that is not the best fuel for your body.”

6. You’ll Be Hungry All The Time

“Not true, eventually. Some people find they are hungry initially, but then adapt over time,” McLeod says.

But researchers have called for further studies on the potential impact intermittent fasting can have on our appetites, particularly around how and when hunger is measured.

Tracee Ellis Ross eating a salad.
(Credit: @traceeellisross)

7. Intermittent Fasting Slows Down Your Metabolism

The idea that intermittent fasting will slow down your metabolism comes from confusion around the science relating to the thermic energy of food. But it’s also incorrect.

“Metabolism is the process by which your body converts food and drink to energy. Intermittent fasting won’t slow it down,” McLeod says.

“If it feels good, you can do intermittent fasting for the rest of your life, non-stop. If that is what works for you, then go right ahead. [However] it is a good idea to check in with your health care professionals as as your needs change over time, you will likely find your food choices need to adjust with it.”

8. Intermittent Fasting Is Really Dangerous And Shouldn’t Be Pursued

Health advice is not always one-size-fits-all, including for intermittent fasting. While it may work well for some people, it won’t be ideal for others.

“This is true for certain individuals. I don’t recommend [it for] those with a history of an eating disorder, or those on certain medications. If you have a condition, always check with your GP first,” says McLeod.

Related stories