Should you eat little and often? Are open cans of food safe to leave in the fridge? Do eggs need refrigerating? Nutritionist Claire Turnbull examines five common beliefs around food and asks, fact or fiction?
While staying with friends recently, it hit me just how many unwritten rules each of us obey when it comes to food. What and when we think we should eat and drink, what we’re happy to keep in the fridge and for how long, and how we prepare certain foods. It sure differs from household to household!
Whether it’s things we’ve learned growing up, picked up along the way, or seen online, before we know it, they become part of how we do things. But not all of them stand up when you take a closer look.
Looks take a look at five common beliefs and whether they really stack up.
1. If you eat every few hours, it speeds up your metabolism
This is one of those things that gets repeated so often it feels like it must be true. Eat more often and you’ll burn your food off faster than someone who eats less often, right?
Well… not really.
When you understand what actually impacts metabolism, you’ll see why this isn’t the case.
Your metabolism can be broken down into three main parts:
Basal metabolism. This is the amount of energy your body uses to keep you alive at complete rest – things like breathing, keeping your heart beating, your brain working, and regulating body temperature. For most people, this accounts for around 60–70% of the energy they use each day.
Physical activity. This is the energy you burn through movement – everything from rolling over in bed, to walking to your car to a workout at the gym. And of course this one varies a lot between people, depending on how active they are.
Thermic effect of food. This is the energy your body uses to digest, absorb, and process food. It’s smaller than many people think, at around 10% of daily energy use.
So yes, eating does require energy, but eating more often doesn’t significantly increase the total amount you burn across the day. In other words, six small meals won’t magically "fire up your metabolism" compared with three, if the total amount of food is the same.
How often you eat depends on what works best for you and allows you to get the balance of nutrition you need, while avoiding being overly hungry and making less helpful food choices. Some people feel great on three meals a day, while others prefer eating a little more or less often.
With the recent rise of intermittent fasting, more people are choosing to eat just twice or sometimes just once a day. But it can be very difficult to get all the nutrients your body needs in a single meal. For most people, eating once a day is not something I would recommend.
If you consistently eat far less than your body needs, your body tends to adapt by using less energy. So not eating enough can actually slow your metabolism, and periods of restriction are sometimes followed by periods of binging, so not eating enough can just fuel an unhealthy relationship with food.
So, what can you do that will support your metabolism? Moving your body more and building muscle with strength training. Activity increases the amount of energy you use, and muscle requires more energy to maintain than fat. This means that having more muscle can help increase your overall energy needs.
As we get older, we naturally lose muscle mass unless we actively work to maintain it. Combined with often moving less, this is a big reason why many people notice changes in weight and energy through midlife and beyond.
2. Eggs don't need to be refrigerated
Eggs are best stored out of direct sunlight at a constant temperature (at or below 15 degrees Celsius), so for many people, this will mean they are best kept in the fridge.
This may, however, vary depending on where you live and how warm it is in your house. When I was living in the North Island, I always stored eggs in the fridge because it was never cold enough to risk keeping them on the bench.
In the bottom of the South Island, where I now live, however, things are quite different. It drops to less than seven degrees overnight in our house for many months of the year, and our garage is basically like a second fridge for five or six months of the year. So here, in the cooler months, I do often leave my eggs out of the fridge as I know they won’t get above 15 degrees.
Another helpful thing to know about storing eggs is that their shells have tiny pores, which means they can pick up odours from strong-smelling foods. For this reason, when they're in the fridge, it’s best to keep them in their carton.
Egg cartons are also best placed on a middle or lower shelf, where the temperature is more consistent than it is in the door of the fridge.
3. You must avoid coffee after 12pm
This is one I hear all the time, but there is nothing magical about 12pm. The idea behind having a rough time to aim to stop drinking coffee, however, is worth understanding.
Caffeine has a long half-life, meaning it breaks down slowly in your body and can stay in your system for quite some time. If you have a coffee, tea or any other caffeinated drink at, say, 7am, around a quarter of the caffeine may still be in your system at 7pm.
Why does this matter? For some people, too much caffeine lingering in the body when you go to bed can make it harder to fall asleep and can impact sleep quality, even if you don’t realise it.
So back to the timing. The reason it’s not necessarily helpful to obey a generic cut-off time is that each of our bodies processes caffeine differenty, and because we all get up and go to bed at different times. For me, 12pm is quite late in the day as I'm a 5am riser and in bed by 9.30pm. But for someone who gets up at 8am and goes to bed at midnight, 12pm is relatively early.
4. Never leave open cans in the fridge
I remember being shocked in my flatting days when I moved into a new place and found that my flatmates had stocked the fridge with open cans – tuna, beans, tomatoes – you name it, it was in there, saved for future eating.
Growing up, this was something I'd been told was a no-no, but what does the science say?
While it’s unlikely to cause harm straight away, it’s not ideal, as there is a small chance that the lining of some cans could react with the food once opened, especially with acidic foods like tomatoes.
So once a can is opened, the food inside should be treated like any other leftover and not kept too long. Food Standards Australia & New Zealand (FSANZ) recommends transferring the contents into a different sealed container before storing it in the fridge.
5. Wash raw chicken before you cook it
This is one many people grew up with, I certainly did, but food safety experts don't actually recommend it.
Washing raw chicken can spread bacteria, as tiny droplets of water can splash bacteria like Campylobacter around your sink, bench and nearby surfaces.
Instead, Food Safety New Zealand recommends patting it dry with a paper towel, throwing the paper towel straight into the bin, and washing your hands before handling other food.
If you do still feel like you want to wash it, the key thing is what happens next. Clean the sink, wipe down surrounding areas, and wash your hands thoroughly.
Claire Turnbull is a registered nutritionist with an honours degree in dietetics, a wellbeing educator and author.
SHARE ME