It's been drummed into us for years. We have breakfast when we rise, lunch around midday and dinner in the evening.
For a while there, we were even told to eat more frequently, with five small meals a day being all the rage.
The pendulum has now swung the other way as the benefits of intermittent fasting continue to emerge. While the popular 5:2 diet recommends drastically slashing calories for two days a week, intermittent fasting can be as simple as skipping a meal.
That one small change may add years to your life.
Such were the findings of research published in January this year in Nature Communications.
Researchers discovered that middle-aged monkeys who fasted from 5pm till 8am had an increased lifespan of, on average, 10 per cent compared to those who didn't fast.
"Cutting your calories delays ageing, probably because the body uses energy from food differently to become more resilient," said Professor Rozalyn Anderson, the study's lead author.
The benefits don't end there, said Mark Mattson, chief of the laboratory of neuroscience at the National Institute on Ageing, in his 2014 TED talk, "Why fasting bolsters brain power".
Firstly, it can lead to weight loss. Sure, you could lose weight by cutting calories at each meal.
But, Mattson says, intermittent fasting "shifts" your metabolism in a way regular eating doesn't.
He says the body only starts burning fat after it's depleted its glycogen stores, which happens after 10-12 hours of not eating.
Intermittent fasting also "does good things for the brain" by increasing the production of proteins in the brain that promote the growth of neurons, while upping energy stores leading to improved memory and learning.
So do we really need three meals a day?
Dr Vicki Kotsirilos doesn't think so.
"There are no hard set rules," says the spokeswoman for the RACGP.
She says each person varies in their body type, along with their nutrient and food needs. Certain populations (such as children, pregnant women and the elderly), have higher nutritional requirements, so they should eat regularly.
But for an "average" fairly sedentary person with no medical co-morbidities, two meals may suffice.
Instead of eating at prescribed times, she believes you should be guided by your body's hunger cues. So if you're not hungry, don't eat just because it's "lunchtime".
But instead of following our appetite, we often adhere to the idea we need three meals a day. That idea stemmed from the industrial revolution, explains Sarah Hyland, general manager of industry services at the Australian Institute of Food Science and Technology.
"Workers needed an early meal to sustain them at work, lunch was an important break in the day and the evening meal became later and more important as the family came together again."
A lot has changed since then – but the idea of three meals persists. So why aren't we advised to skip meals more often? Mattson says there's no financial gain to the food industry to do that, so we're sold the idea we need such regular meals.
That's not to say intermittent fasting is a good idea for everyone. O'Dell warns it can lead to increasing hunger and poor food choices later.
"A very common diet pattern of overweight, busy people is to not eat until about 2-3pm, which is usually a large meal, followed by an even larger dinner.
"In this instance, people consume a considerable number of calories in a small window in the day which seems to encourage the body to store more energy and gain weight."
If you're planning to skip meals, O'Dell warns not to skimp on brekky as it's well documented that breakfast eaters tend to be slimmer than those who forgo their morning meal.
But instead of worrying about the number of times we eat a day, Dr Kotsirilos says we should focus more on the type of food that comprises each meal.
There's no point eating less frequently if you fill your belly with processed, nutrient-poor options at those meals.
If eating less regularly appeals to you, speak to your doctor. Then, don't dive in too quickly.
Mattson likens it to exercise, saying you wouldn't feel good after going on a long run if you've never exercised. Instead, he advises skipping a meal a day once a week for a month, then doing that for two days a week, slowly adapting over time.
"And you'll find on the days that you don't eat so much, you're more productive."