Why is it we crave chocolate and hot chips … and never broccoli? And why is it hard to stop at just one bite? Paula Goodyer explains why some foods are so irresistible.
Doesn’t it seem strange that even though we’re well aware of the health risks of eating too many over-processed foods, on average over a third of the kilojoules we eat every day comes from foods like biscuits, lollies, fast food, salty snack foods and soft drinks, according to the latest National Nutrition Survey. So, why do we keep eating them?
Many of these foods have been found to be the most addictive to us. Chocolate, pizza, ice cream, French fries, biscuits and chips topped the list in a recent US study (see The 10 most addictive foods, below). These highly processed foods are all rich in fat and sugar or salt, and low in fibre — the exact opposite of the foods rated as the least addictive, which included broccoli, brown rice, carrots and bananas.
But too much fat, sugar or salt aren’t the only things the most addictive foods have in common. They also have a high glycaemic load — meaning they are rapidly absorbed into the blood stream, creating high spikes in blood sugar. This is linked to ‘addictive-like’ eating, say the researchers.
Are we all ‘addicted’?
Studies have found similarities between drug dependence and addictive behaviour with food. Having difficulty controlling how much we eat of certain foods is one similarity; and continuing to overeat despite serious health problems is another.
In a US experiment, researchers found naloxone, a drug used to treat heroin addiction, also cut cravings for sweet foods.
“But the jury’s out on whether food addiction really exists — there’s not a lot of hard evidence,” says Dr Tracy Burrows, Accredited Practising Dietitian and senior lecturer in Nutrition and Dietetics at the University of Newcastle.
“Research shows nutrient-poor, highly processed foods with a lot of sugar, fat and salt are most likely to be linked to addictive behaviour to food. Studies show that in some people, these foods stimulate the brain to produce ‘feel good’ brain chemicals, in the same way that drugs do.”
Many experts suggest that we’re genetically programmed to overeat foods that are sweet, fatty and salty because high-kilojoule foods were in short supply in our caveman days. Thus, when we found these foods, we needed to eat as much of them as we could. In other words, overeating isn’t so much about willpower as it is about biology.
But this doesn’t explain why not everyone overeats these foods, Dr Burrows says. “We’re all exposed to the same food supply, yet only around 20 per cent of us fit the criteria for addictive behaviour with food. People have different drives for overeating. So, is it something in food that’s potentially addictive or is it more to do with habit — like associating sitting on the couch with eating a bag of chips?” says Dr Burrows.
What makes some foods irresistible?
While some foods cause the brain to release ‘feel good’ chemicals, there are a few other reasons why we find it easy to overeat pizza — and hard to binge on broccoli. “For starters, junk food usually requires a lot less chewing than whole foods, so it goes down a lot quicker and easier,” Dr Burrows says.
The intense ‘moreish’ flavours of highly processed food can leave our taste buds longing for more — and override our innate ‘I’ve had enough’ signals. Adding salt to fatty foods can suppress the body’s satiety mechanisms, thus encouraging us to overeat, according to researchers at Deakin University in Victoria.
Dr David Kessler, former commissioner of the US Food and Drug Administration, took the food industry to task in his book, The End of Overeating. He accused it of contributing to obesity by engineering food to be easy to overeat, by layering flavour on flavour — on flavour.
As an example, he tells how one US restaurant chain amped up the flavour of its chicken wings: the chicken meat is first pumped with additives to bulk it up and make it softer. Then it’s battered, crumbed, fried — and marinated with a sauce made with sugar, hoisin sauce, soy sauce, chilli paste, modified food starch and concentrated orange juice. And if that’s not enough, it’s served with a dressing made of mayo, buttermilk and wasabi.
The 10 ‘most addictive’ foods
Students in a study at the University of Michigan were asked to rate foods based on symptoms of addictive-like eating such as: ‘eating more than they should’, ‘being unable to ‘quit’ a food’, and ‘showing an increased ‘tolerance’ towards a food’. These were the foods they rated as the most problematic.
The 10 ‘least addictive’ foods
Beans (no sauce)
Corn (no butter or salt)
The hidden punch behind the crunch
The crunch factor can also help hook our taste buds. Like Dr Kessler’s example of chicken wings, many highly processed and fast foods are baked, fried or toasted to create crispy textures which are easy to overeat. But crunchiness often comes with a cost, says Associate Professor Melinda Coughlan, head of the Glycation, Nutrition and Metabolism Laboratory at the Baker IDI Heart and Diabetes Institute in Melbourne, Victoria.
Cooking foods at high temperatures, especially meat that is high in fat and protein, produces compounds called Advanced Glycation End products (AGEs). Diets high in AGEs are linked to a higher risk of chronic disease, Prof Coughlan explains. Sugary and highly processed foods can also be high in AGEs.
“We can’t say for sure what the impact of a high-AGE diet is, but studies have shown that it increases inflammation and oxidative stress in the body, and we know that these are closely linked to type 2 diabetes and obesity,” says Prof Coughlan.
The bite on your health
We’ve often been told that eating too many highly processed foods can cause weight gain and increase the risk of heart disease. But science has now dug deeper to find more reasons to avoid these foods — too much added salt, for instance, not only troubles our arteries, but may also harm our immune system.
“We’re looking at the impact of too much salt on the immune system, and whether reducing salt can lower the risk of autoimmune diseases such as multiple sclerosis,” says Dr Katrina Binger of the University of Melbourne’s Department of Biochemistry and Molecular Biology, who has found that a high salt intake can interfere with wound healing.
Research is also looking at the effects on our gut microbes — the bacteria now known to influence our health, including our immune system. There’s growing evidence that Western diets with too little fibre and too much saturated fat are disrupting the balance of these important microbes and driving the rise in allergies and autoimmune disease.
Teaching taste buds
If we’re accustomed to eating less healthy foods on a regular basis, it can be hard to break the habit. Our taste buds don’t light up for fresh vegetables and unsweetened yoghurt the way they do for a burger or packet of chips. But they can.
Retraining our taste buds to enjoy food without adding salt or sugar takes around three weeks. To get you started, just follow our five-step plan towards a healthier way of eating…
1. Don’t go cold turkey
Gradually introduce more whole foods into your diet each day. Start by replacing the salty snacks with fresh fruit.
Then, as your taste buds are adjusting, move on to include more fresh vegies, especially those that are in season, as they have more flavour, says Tania Ferraretto, Accredited Practising Dietitian and spokesperson for the Dietitians Association of Australia. Try salads for lunch, and load up your plate with vegies at dinnertime.
“Your taste buds are very adaptable. It takes about three weeks to adjust to eating less salt. Use herbs and spices to make it easier,” says Ferraretto.
2. Know what you’re really eating
“Make a note of what you eat and drink over a few days by writing it down or using a food diary app,” says Dr Tracy Burrows, senior lecturer in Nutrition and Dietetics at the University of Newcastle. “You might think that you eat healthily, but then there’s that takeaway on Monday, a night out with friends on Tuesday, and cake in the office on Thursday.
“It’s not until you note it down that you can see what you’ve really been eating all week.”
3. Beware of processed foods in disguise
Words such as ‘natural’ or ‘superfood’ don’t guarantee that a food has a healthy amount of sugar, salt or fat. So, always check the ingredients list to see exactly what the product contains.
4. Read the label
Not everything sold in packets is over-processed — rolled oats, natural muesli, wholegrain bread, frozen vegetables and fruit, as well as many dairy foods (the unsweetened kind) are just some examples of minimally processed foods, Ferraretto says. Read the ingredients list on the back of the pack. And if salt or sugar is in the top three, or there is a long list of additives, leave it on the shelf.
5. Make healthy eating convenient
We often rely on over-processed or fast food because it’s quick and ready to eat.
Yet, there are so many healthy options that are just as convenient, such as frozen vegetables, cans of tuna and chickpeas, tinned tomatoes and microwavable rice blends.