When choosing what to eat, we all know fresh, unprocessed food is probably best.
After all, processed foods usually contain more sugar, salt and fat than their unprocessed counterparts, all of which can cause our waistlines to bulge.
But there’s another reason why processed foods can make us gain weight: because of the preservatives they contain.
Those were the findings of new research published in Nature Communications.
The research found that preservatives interfere with our hormones, disrupting the process that tells us when we’re full.
They do that by distorting the chemical structure of those ‘signalling’ hormones. That disables the process by which hormones are transported out of cells, making them ineffective.
Without that signal telling us we’re full, we’re more likely to keep eating and gain weight.
“This is a landmark study that substantially improves our understanding of how endocrine disrupters may damage human hormonal systems and contribute to the obesity epidemic…” said Clive Svendsen, director of the institute.
For the study, investigators used hormone-producing tissues grown from human stem cells.
They then exposed the tissues to three different types of chemicals, including Butylhydroxytoluene (BHT) which is commonly added to breakfast cereals and other foods.
The other two chemicals they investigated can be found in seafood and cookware.
Of the chemicals tested, BHT produced some of the strongest detrimental effects, said investigator Dhruv Sareen.
The problem these days is that most foods we eat contain some level of preservatives, says dietitian Kathryn Hawkins.
She says preservatives play an important role in preventing health risks from food being spoiled or becoming toxic.
But some foods contain more preservatives than others.
Foods with the highest amounts of preservatives include canned foods, processed meats, cheese and wine, Hawkins says.
So if preservatives can mess with our hormones and cause us to overeat, should we try to eliminate them from our diet altogether?
Such an aim is unrealistic, says Hawkins.
However, she says there are steps we can take to minimise our intake.
Firstly, we should aim for the majority of our diet to be fresh food.
Then, we should wash fruit well before eating it, opt for organic meats and eggs and include plenty of legumes and nuts.
Scouring farmer’s markets for preservative-free food and making foods like bread from scratch at home can also help.
But even Hawkins says we don’t have to be evangelical.
“It takes a lot of preparation, organisation and a bit of extra time, and not everyone can do this every day!”
Of course, going organic is also an option, though she notes such options are not always “completely chemical-free”.
Or we could opt for foods that use natural preservatives.
They include substances such as salt, sugar, lemon juice, vinegar and rosemary extract.
But they’re not perfect, either.
“Obviously salt is not ‘better’ for us [than other preservatives],” says Hawkins, who explains that a high salt intake is associated with high blood pressure and cardiovascular disease.
“Sugar is also not appropriate to eat in large quantities.”
Perhaps the ‘best’ preservative is ascorbic acid, also known as vitamin C, says Hawkins.
While it’s commonly used in bread, jams, fruit juices and other snack food, she says its use as a preservative is limited.
(That’s because, in high doses there is a risk of vitamin C toxicity. Plus its flavour can affect the taste of food.)
Instead of trying to find the ideal preservative or eliminate our intake of them altogether, Hawkins believes our focus should simply be trying to eat well.
If you’re worried about how preservatives are affecting your weight, she says your best bet is to cut back on foods that both contain preservatives and offer minimal nutrition, such as sweets and packaged snacks.
You should then consider the health and nutritional benefits of what you choose to eat.
If you opt for fresh, minimally processed foods, you will naturally reduce your intake of preservatives while filling your body with healthier options.
And that can only be good news for your waist.