Golden monkeys in China

Dieting - why it's not really about calories, low fat, keto or paleo

3 August 2021

Why people in developed nations can’t keep off the kilos

Public enemy number one in the modern world is the weighing scale. Every diet has been tried, yet the kilos multiply and diabetes, heart disease are still prevalent. Is there something we're missing?

Remember when low fat seemed like the answer? Then the research was stretched out of shape by an international food industry dazzled by the massive profit potential of low-fat product lines and soon, low fat became its own problem.

At least now we know the real problem is sugar. Or is it?

Don’t look for an easy answer from Professor David Raubenheimer. Yes. He is a world expert on human and animal nutrition, but his work, at its core, has always been about getting the world to accept that there are no clear-cut dietary villains.

“We’ve been treating this like an engineering problem,” says Raubenheimer. “Tell people to eat less fat and problem solved. But we’re not dealing with a linear system here. Animal nutrition, human nutrition, is an ecology. You have to factor in all the players.”

Searching the natural world for answers on human nutrition: “I was in a medieval village on the Nepalese Himalaya. We were working on snow leopards and tracking their main prey, the blue sheep."                                Photo credit: D Raubenheimer.

The comparison can be made to how an animal in nature is affected by its food environment: where the animal forages; the season; the weather; the action of other animals. Humans aren’t so different. We also forage, but in supermarkets and restaurants, and what we find to eat in our landscape is affected by the actions of culture, governments and the food industry.

An insight into the problems in the human foraging landscape came in a 2019 Deakin University study which found junk foods are discounted by supermarkets, on average, twice as often as healthy foods. A clear case of industry changing the human food environment and driving bad choices.

Looking for answers

These ideas are investigated in an emerging discipline called nutritional ecology, and throughout his career, Raubenheimer has been gathering evidence to define and test its implications. One question has particularly motivated him: why is the developed world in the continuing grip of an obesity and diabetes epidemic?

Part of the answer could be that there is a fundamental misunderstanding of our main driver for eating.

“It’s grossly over simplistic to say animals, humans included, eat for energy. That’s fundamentally untrue in biology,” says Raubenheimer who came to the University to take up the Leonard P Ullmann Chair in Nutritional Ecology, which was established through the sale of a painting by Picasso, Jeune fille endormie, provided by an anonymous donor.

“Humans, like many other species, actually have a stronger appetite for protein than for the main energy-providing nutrients, fats and carbohydrates. That means that if the protein in our diet is diluted with fats and carbs, we will eat more energy to get the protein that our bodies crave.”

A good illustration is that universal favourite, hot chips. Consider somebody who needs 75 grams of protein daily. To get this on a diet with 15% protein - say vegetables, rice and fish - she would need to eat 2000 calories of energy, which is the daily energy intake recommended for women.

“But if she was trying to get the same amount of protein from chips, which contain only 5% protein, she would need to eat a whopping 6000 calories.” Says Raubenheimer. Three times more calories than recommended!”  

David Raubenheimer and Stephen Simpson's research culminates in a unifying theory of nutrition in their book Eat Like the Animals.

This mechanism, now called the ‘protein leverage hypothesis’, was identified by Raubenheimer with his colleague of 35 years standing, Professor Stephen Simpson, who is the academic director of the Charles Perkins Centre. Together, they’ve written books and numerous papers on the subject of nutrition, including their latest book, Eat Like the Animals, now translated into nine languages.

“Steve is a brilliant experimentalist. He’s more on the lab side, the mechanistic side of biology; I’m more on the ecological, evolutionary side,” says Raubenheimer. “But we know enough about each other’s expertise to speak a common language.”

So, why is protein such a driver of appetite?

Proteins are part of almost every element and function in our bodies. They’re in the structure of our cells, present in enzymes and hormones and active participants in our immune responses. Mapping the human genome with its 20,000 genes was a huge achievement. The protein equivalent is called the proteome. It’s estimated to have over a million expressions of protein that build the human body and allow it to function.

This is how enmeshed protein is in the functioning of the human body. Is it any wonder we hunger for it?

“The protein mechanism in appetite is a revolutionary insight,” he says. “Obesity, diabetes, cardiovascular disease - they’re all driven by diet and we have to use what we’re learning to bring them under control.”

Observing nutritional geometry

The quest is being pursued in the labs of the University’s Charles Perkins Centre, but for years, Raubenheimer has sought knowledge in some of the most remote places on the planet, travelling from the lush and humid jungles of Borneo to the austere peaks of the Himalayas.

His last, pre-COVID trip was working with a group of hunter gatherers in the Congo basin. “I stayed with them for several weeks,” he says. “They’re very healthy people because of their diet. But they face other dangers. A man was killed by a falling tree shortly after I left, and a young girl, barely two years old, died of a tooth infection.”

Professor Raubenheimer with hunter gatherers in the Congo basin.
Photo credit: D Raubenheimer.

These trips offer few comforts (“It can be a bare bones existence. You need to be ready to tolerate exertion, heat, cold and hunger”) but as a youngster growing up in his native South Africa, Raubenheimer was already an eager hiker with a passion for the natural world.

The wild places he most often goes to are where he can observe primates; gorillas, orangutans, chimpanzees, lots of species of monkeys and baboons, “Not just because they’re very like us,” he says. “But because they habituate. In time, they regard you as just a normal part of the environment, so long as you treat them correctly, and you behave correctly.”

Here Raubenheimer describes a typical day observing an orangutan:

“We get up at half past three or four and head into the forest before the sun comes up to locate an orangutan that we’d previously identified. She’d still be up a tree in her sleeping nest, so we string up hammocks around the tree and wait until she wakes.”

When the orangutan finally wakes and starts feeding, the observation team is on.

“We record everything she does. Everything she eats. What she excretes. We take samples for nutritional analysis, chemical analysis, then translate those very detailed observations into the nutritional geometry models that we have created to give shape to the information.”

Nutritional geometry was created by Raubenheimer and Simpson as a graphical tool to represent complex nutritional information and allow the outcomes of changes to be predicted.

So, if these two nutritional thought leaders agree that the answer isn’t low fat, low sugar, low carb, keto or paleo, what is it? Again, we return to the word ‘ecology’ and the ecology of the Western diet.

The natural food ecology of an orangutan presents it with fruit, young leaves and sometimes insects. The food ecology of many humans presents us with highly refined, high sugar, high fat foods – all of which dilute the protein in our diets. That leads to over-consumption and the all too familiar diseases of the Western diet.

“This isn’t really about individuals gaining or losing weight,” says Raubenheimer who is establishing the Centre of Excellence for Food System Transformation to solve problems of the Western diet through ecological methods.

“Governments should use tools like taxation, subsidies, labelling laws and health education; industry should prioritise the production of affordable, healthy foods; and consumers should use their purchasing decisions to push government and industry into making healthy eating easier.”

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