Near-balanced diets by cockroaches can teach us plenty about eating well

You may have more in common with cockroaches than you realise.

In an experiment, researchers first manipulated cockroach diets so they were either being fed exclusively a high protein, high carbohydrate, or a near-balanced food — putting them in different states of nutritional imbalance.

Then they were given access to all three foods, enabling them to mix whatever diet they wished.

Amazingly, all three groups of cockroaches selected just the right combination of the three foods to rebalance their diets, and then continued to eat according to that ratio.

What this tells us is that cockroaches — and the 40 or so other animal species the researchers have studied — have not just a single appetite, they have appetites that make them hungry for specific nutrients depending on what they need at a given time.

And interestingly, humans have these nutrient-specific appetites too.

It's insights like this gleaned from the natural world that are helping us better understand why we overeat and how imbalances in our modern food system are contributing to the problem.

A 'food system' is an immensely complex set of interacting factors that surround every food and meal that we eat.

Broadly speaking, food systems can be partitioned into those factors that influence what we eat — such as the availability, tastiness and affordability of different foods — and those factors that are influenced by what we eat — such as the economic and environmental consequences of our dietary choices.

One of the greatest challenges we're facing in Australia and globally is that the factors that influence what we eat are configured in such a way that some outcomes are optimised at the expense of others. The production and marketing of foods, as well the policies regulating these, are optimised for economic benefit, often at a cost to the environment and public health.

We need to find a way to rebalance the food system.

And to do that, researchers are turning to what we might learn from how other species navigate the complexity of natural food systems — ecosystems — and how these findings apply to our own species.

For example, in their research on our closest living cousins in the wild — other primate species — they found that owing to natural ecological fluctuations (such as the changing seasons) primates are regularly stuck in imbalanced food environments that prevent them from eating a balanced diet.

In such circumstances, most primates prioritise their intake of protein more strongly than the two other macronutrients we need — fat and carbohydrates.

In other words, their appetites regulate their intake of protein more strongly than fat and carbohydrates, and as a result on low protein diets they will overeat fat and carbohydrates, and on high protein diets they will undereat fat and carbohydrates.

Humans also show protein prioritisation, so we're no different to other primate species in that respect.

Why this matters is it helps us understand in an entirely different way why it is that we overeat in our modern food systems. Surprisingly, we don't overeat fats and carbs because we have particularly strong appetites for those nutrients, but because we have a stronger appetite for protein!

As we reduce the percentage of protein in our diets, to maintain our protein intake around normal levels the amount of fats and carbohydrates we eat increases exponentially.

It's not because there's something wrong with our biology that needs a pharmaceutical or other approach to deal with — our biology is intact, the same as our wild primate cousins.

What has changed to drive the nutritional predicament we're in today is the environment we find ourselves in.

Protein has been diluted in our food system, leading to the epidemic of overconsumption that's plaguing the planet and the health of our species.

According to The Australian Dietary Guidelines, we should be getting between 15 and 25 percent of our energy intake from protein, between 45 to 65 percent from carbohydrates and between 20 to 35 percent from fats.

This allows us to identify at a glance whether the composition of our diet, or a particular food or meal is balanced nutritionally with respect to these recommendations.

And allows us to identify which categories of foods are responsible for the protein dilution in our food system.

What research has shown is that it's ultra processed foods that are the culprit for diluting the protein concentration in our diets in the Australian and the global food system.

Ultra processed foods are foods that originate not from a forest or from a field but from a factory. They have their roots in industrial manufacture, not in agriculture or in harvesting from the wild.

They are designed by food engineers not to nourish human bodies or protect the environment, but to nourish and protect the financial returns for shareholders.

Unfortunately, from an affordability perspective what research has shown is that low income groups in Australia are associated with low protein diets and hence spontaneous excess energy intake.

They're also more likely to be gravitating towards these ultra processed foods.

The reason for that is that when you compare the relative cost of the different macronutrients in the foods that we eat, protein is the expensive one.

Avoiding obesity then becomes a socio-economic challenge, with people on lower incomes forced away from the recommended protein intake and towards overeating of fats and carbohydrates.

Understanding that we prioritise protein is also important when considering the environmental impacts of the diets that we eat.

High protein foods are associated with high greenhouse gas emissions, so you might assume that we should be reducing the density of protein in our diets in order to also reduce our greenhouse gas emissions.

But this assumes that our energy intake remains constant as the proportion of protein in our diet decreases, which we know is not true.

It is our protein intake which remains more constant, so as we dilute the proportion of protein in our diet our energy intake increases.

If we reanalyse the data in those terms we find that reducing protein in the diet will reduce greenhouse gas emissions, but only if high protein foods are replaced by real plant-derived foods, such as vegetables, grains, fruit and pulses.

If high protein foods are replaced by ultra processed foods, environmental damage is not reduced, and can even be worse.

One reason for this is the energy used in the industrial production of ultra processed foods. Another reason is their low protein content leads to overconsumption — and the production of each additional calorie eaten produces greenhouse gases.

Real foods that are low in protein, such as vegetables and grains, are not overeaten in the same way, because they contain gut-filling fibre.

So ultra processed foods are low in protein, high in energy, and damaging to the environment.

And there's another problem — their nutrient density is at an absolute rock bottom, whereas it's diets rich in wholefoods that peak in these health-giving substances.

Why then do we tolerate diets that are unhealthy and unsustainable?

Nobody really wants the planet to be poisoned. Nobody wants our bodies to be poisoned. Yet both outcomes are so persistent within our food system.

This is because they are deeply bedded within the economic system that governs all of this, such that there are market benefits to the economy of having ultra processed foods consumed at the high levels they are.

Market benefits are, of course, good for the country — but at what cost to public and planetary health?

The key challenge then is to manage the drivers of our food system in such a way that the economic, health and environmental benefits are better balanced.

Policy tools are available for this, and are already being implemented in some countries. These include health taxes (based for example on the amount of added sugar), front of package warning labels, restrictions on marketing and distribution, and media campaigns.

No one of these will on its own address the problem. They need to be interlinked in sets of reinforcing strategies, as is being done in Chile and Brazil.

Such tools are no stranger to Australia. They have been used to good effect to reduce tobacco, and to some extent, alcohol consumption.

Similar measures applied to food will help reduce the burden of preventable disease and save the natural world on which we rely for producing food.

Including those species, such as insects and apes, that have helped us understand how we have gone wrong and where we can do better.

Professor David Raubenheimer is the Leonard P Ullmann Chair in Nutritional Ecology at The University of Sydney. His studies of insects, fish, birds and a variety of mammals have helped develop a new approach to human nutrition-related problems, such as the dietary causes of obesity. He has published over 300 scientific papers, and has co-authored two books with close collaborator Professor Stephen Simpson, most recently 2020's Eat Like the Animals. This research was undertaken with financial assistance from the Australian Research Council (ARC), the Australian National Health and Medical Research Council (NHMRC), and the Meat and Livestock Association of Australia.