Ask Angie: 9 questions about intermittent fasting
As a dietitian, I find it funny that one of the topics I’m asked about the most doesn’t involve eating at all – intermittent fasting.
Some tout it as a silver bullet for weight loss and longevity. To others, it’s a dangerous diet fad. To the billions of people who undertake religious fasts like Ramadan every year, it’s primarily a spiritual pursuit.
I know you have a lot of questions, so I’m here to answer the big ones for you. Spoiler: it’s complicated.
1. What is intermittent fasting?
Intermittent fasting is an umbrella term that refers to many different ways of eating, all of which require alternating between structured periods of eating with periods of – you guessed it – fasting.
The most common type is probably time-restricted feeding like the 16:8 method, which involves fasting for 16 hours and eating during an 8-hour window.
Luke uses the 16:8 method during a ‘cut’ or strict diet period, but not when he’s trying to build serious muscle.
Some other popular kinds of fasting are alternate day fasts (eating normally for 24 hours followed by eating nothing for 24 hours) and the 5:2 method (restricting calories on two days and eating normally for five days).
2. Why is intermittent fasting such a big deal?
Fasting is by no means new, but most of the people I speak to are interested in it as a way of losing (or managing) weight.
It’s not hard to see what makes fasting so attractive to dieters. There’s no tracking of calories, macros, portioning out food or cutting out certain food groups. You simply stop eating for a set period of time and then start eating again!
Simple, right? Not so fast…
3. Is fasting good for you?
I’d love to give you a definitive answer, but the research is far from conclusive.
There’s a lot of hype around fasting, but the reality is that what we don’t know far outweighs what we do. While we are seeing more research conducted with human subjects, the majority of these studies tend to be small and short-term.
More long-term research on humans is needed to understand the real impacts, or to support the claims made by many about the alleged benefits.
Success doesn’t require dramatic changes. Try my small, sustainable hacks for every goal type.
4. Who can safely try intermittent fasting?
There are several groups of people who should avoid intermittent fasting.
If you have type 1 diabetes, are pregnant or breastfeeding, or use medications that must be taken with food, fasting may be harmful to your health.
If you have a history of disordered eating, I do not recommend you try intermittent fasting.
Even though fasting doesn’t place any food groups ‘off limits’, it is still a form of restriction. If you’ve ever struggled with an unhealthy obsession with food, including extreme diets or harmful eating habits, fasting could be a trigger.
If you do not fall into any of the categories above, trying fasting is unlikely to do you any long term harm.
5. Is intermittent fasting a good way to lose weight?
Research shows that fasting is no more effective than a calorie deficit (consuming less than you burn) for weight loss.
But if you find a traditional calorie deficit difficult to stick to, intermittent fasting could be useful for achieving your goal.
Let’s say you’ve got a sweet tooth that regularly kicks in around 8pm. Fasting in the evening might make it easier for you to avoid a snack attack by placing all food off limits at that time of day.
Remember, intermittent fasting isn’t magic. For some people, it just makes it easier to eat less overall without thinking about it.
6. Can you build muscle while intermittent fasting?
This one has been popping up in the Centr community quite a bit lately!
But if your overall goal is to build muscle, I don’t recommend intermittent fasting.
Fasting makes it hard for muscle builders to consume enough calories and protein. Speaking of protein, have you tried these dinners?
Partly, that’s because the research in this area is still lacking. The majority of studies on fasting look at overweight or obese adults who want to lose weight, not people trying to build muscle.
It’s also not practical for most people since it’s harder to consume the calories and nutrients you need to build muscle while eating in a restricted window.
However, if your goal is to lose fat while maintaining existing muscle mass (not stacking on more), it could be an effective tool.
7. Should I work out in a fasted state?
Based on the current research, my recommendation is that if you want to perform at your best, you should eat before exercise.
Most people perform better after a pre-workout snack. The Quick Banana & Chia Toast is one of my faves.
This is particularly important if your training session lasts longer than 90 minutes, as training for that long without eating beforehand is associated with increased breakdown of muscle for fuel.
If you really want to give fasted training a try, I’d stick to low-intensity sessions of 60 minutes or less and closely monitor how you feel.
8. Does fasting impact men and women differently?
Women should tread carefully when it comes to fasts that last 24 hours or more.
Prolonged fasts are shown to increase insulin resistance in women, which can lead to health issues such as high blood pressure, high cholesterol and type 2 diabetes.
The reproductive hormones that play an essential role in women’s bodily functions such as metabolism and ovulation may also be negatively impacted during longer fasts.
For example, estrogen (oestrogen) tends to decrease with intermittent fasting, which can lead to increased fat storage and appetite – the exact opposite of what you’re probably trying to achieve.
9. What are some unexpected drawbacks of fasting?
Okay, you got me – no one ever asks me this.
But there’s an aspect of intermittent fasting that I think gets overlooked: the impact it can have on your relationships.
In general, I’m not a fan of diets that make socializing more difficult. If you’re someone who enjoys eating out with friends and family, it’s important to consider how intermittent fasting might interfere with that.
If you have young children at home, think about those little eyes watching. How does it look to them if they see you skipping breakfast or dinner, or avoiding family events because of your diet?
If you have questions or concerns about fasting and your individual health situation, be sure to speak to an accredited dietitian or your doctor.
Sports dietitian Angie Asche will power your plate with no-nonsense food advice. Founder of Eleat Sports Nutrition, Angie works with MLB, NFL and NHL athletes to get the best from their bodies. With a Masters of Science in Nutrition & Physical Performance, and as a certified exercise physiologist and personal trainer, she’s got the expertise you need to achieve your goals.
Start your Centr journey with a 7-day free trial
Get Chris Hemsworth's team of the world's best trainers, chefs and well-being experts in your corner.