The fight against fat
By Chris Rodley
It was a slow and laborious start to a scientific career. As a young PhD candidate studying the diet of locusts, Steve Simpson needed to make detailed observations of their feeding habits. So for six days and nights, he isolated himself in a heated room with 10 of the insects and carefully measured their every meal and dropping, working around the clock except for an hour’s nap each day.
By the end of that exhausting week, he had gathered an impressive collection of data. Although he did not realise it at the time, it was the first step in an epic journey of scientific discovery that led from understanding the behaviour of locusts to new paradigms for thinking about nutrition, human obesity and why we grow old.
Professor Simpson is now an Australian Research Council (ARC) Laureate Fellow in the School of Biological Sciences and a former NSW Australian Scientist of the Year. In February, he received another honour with his appointment to the helm of the Charles Perkins Centre, the University’s new research hub for the study of obesity, diabetes and cardiovascular disease. His international reputation in nutrition, as well as his multidisciplinary approach to science, made him an ideal fit for a centre which seeks to bring together divergent areas of study.
As academic director, he will control an unprecedented research effort to tackle obesity, diabetes and cardiovascular disease, which are “among the greatest threats to health and quality of life” facing humanity, he says. In Australia, where more than 60 per cent of adults are overweight or obese, they are particularly urgent challenges.
To drive forward the ambitious research agenda, at least seven new academic chairs are being launched. Chairs in nutrition, psychology and metabolism will be created using funds from the sale of the Picasso painting donated by an anonymous benefactor last year. Other chairs will span across the disciplines of arts and social sciences, applied economics and health sciences, while the Australian Diabetes Council is funding a new chair to spearhead diabetes research.
“It is exceptionally rare for this number of new chairs to be advertised at once,” says Professor Simpson. “It makes a very large statement about the ambition and commitment of the Centre, as well as the generosity of donors who have proven willing to share our vision.” The search for top international talent to fill the new positions has already begun and is expected to inspire some intense competition.
“We want to do is demystify the clamour of conflicting advice that people receive on diet and lifestyle.”
But why should the University of Sydney expect to solve such complex problems where so many others have failed? Other initiatives around the world have tended to focus mainly on the genetic and cellular basis of obesity, diabetes and cardiovascular disease, he says, but the conditions are much more complicated than just their biology.
“What we need to understand is how human biology interacts with the environment,” he says. “We must look at how our psychology, social and economic pressures, urban planning, education, agriculture, the food industry, media and government all play a role in disease.”
The Centre will unite scholars in all these areas and more, enabling “a new era of collaboration” to begin, according to the researcher. “It’s the interfaces between disciplines that are going to create the really new and interesting breakthroughs in this area,” he says. “That is what excites me so much about the project.”
His first priority will be to identify networks of academics across the University working on the three conditions and encourage a “mesh” of new partnerships between them. He will also look outside the University to form collaborations with government agencies, health and education systems, policy-makers, not-for-profit agencies and industry.
Another focus will be on public outreach to help us as individuals make better lifestyle choices. “One of the really important things we want to do is demystify the clamour of conflicting advice that people receive on diet and lifestyle,” Professor Simpson says. “We need a dispassionate presentation of our current understanding that’s unpolluted by vested interests.”
Two research projects in this area are already underway: one is using social media to teach us how to balance our diet, the other working with Aboriginal communities to find new ways to promote nutritious eating.
The “Eureka moment”
He says his leadership role represents a “once-in-a-career” opportunity to translate his research philosophy onto a much wider canvas. “This may be the University’s most ambitious project of the past 100 years,” he says. “It is happening at a half-a-billion-dollar scale that I could never have imagined.”
This career trajectory all started with a love of insects in early childhood, says Professor Simpson: “From the age of three, I was telling relatives that I wanted to grow up to become an entomologist.” His passion only increased when his parents moved from Melbourne to subtropical Brisbane, where an abundance of moths and beetles would gather each night around the light above the family dinner table: “There was never any question I would go on to study insects at university.”
On completing his undergraduate degree at the University of Queensland, he moved to the University of London where he received his PhD for his work on locust feeding. Following a brief detour into experimental psychology during his postdoctoral research, he returned to the study of locusts again when he joined the Department of Zoology at Oxford.
A turning point in his research came when he began investigating why locust plagues were devastating crops in North Africa. He eventually discovered that the locusts were swarming because they were on a desperate mission to find protein, which was causing the insects to cannibalise each other. Once they ate enough protein to satisfy themselves, the cannibalism ended and the swarm subsided.
It was to be a breakthrough with far-reaching implications. Over the following years, Professor Simpson went on to show that a diverse range of other animals – from fish to mice, cats and monkeys – have distinct appetites for the macronutrients of protein, fat and carbohydrates, which they constantly aim to satisfy. Of the three appetites, the hunger for protein is particularly strong: if an animal’s diet becomes dominated by carbohydrate or fat, it keeps eating until it hits its target level of protein.
Professor Simpson clearly recalls the “Eureka moment” that led him to develop his model for how organisms regulate their appetites for different nutritional targets. “I was sitting in Oxford one day with a messy data set from our locust studies, and saw with beautiful clarity how target-like regulation of nutrient intake emerged,” he says. “It had been there all along, but you needed the right lens to view it.”
After sealing his reputation with his new model for nutrition, developed in collaboration with colleague Professor David Raubenheimer, he was lured back to Australia in 2005 to become an ARC Federation Fellow at the University of Sydney. Here he has focused on expanding the scope of his work in several exciting new directions, particular in the area of human health.
While his previous work at Oxford had suggested that our protein appetite could be a key reason why humans overeat, Professor Simpson did not yet have firm evidence. To prove his ideas, he instigated a major study of human nutrition at the University’s Woolcock Institute. In the experiment, his team fed participants either low, medium or high-protein menus, which were otherwise matched for taste and appearance, and observed how much they ate over week-long periods. He found that those on a diet of 10 per cent protein consumed significantly more calories than participants on a 15 per cent protein diet – and also turned to more savoury snacks to satisfy their protein craving. It was just the effect that his protein hypothesis predicted.
A nutritious balancing act
According to Professor Simpson, that hypothesis provides a compelling explanation for the spiralling rates of obesity seen across many developed nations. The growing availability of cheap, palatable foods that are low in protein but high in fat and carbohydrates has caused us to eat more total calories in order to satisfy our strong protein appetite.
Through a parallel line of enquiry, Professor Simpson and his collaborators have also uncovered a biological explanation for why humans and many other animals are so reluctant to overeat protein. In an experiment funded by the National Health and Medical Research Council, his group fed mice on a high protein diet across their entire lifespan and observed how they fared. As expected, the mice ate fewer total calories than those in the control group – but they also ended up dying earlier.
It is a finding with revolutionary implications for the study of longevity, Professor Simpson believes. “The central prevailing dogma in this field to date has been caloric restriction: if you reduce calories you will live longer,” he says. “But what we have shown is that it’s the ratio of protein to carbohydrate that is critical in ageing. The higher that ratio, the less long organisms live.”
All this creates a paradox for those seeking practical nutrition advice from research. For while his work implies that a higher protein diet can help us avoid overeating, it also suggests that high levels of protein may shorten our lives. “Nutrition is a balancing act,” he responds. “Our aim has to be to understand where the fulcrum lies.”
“We need to understand the ‘language of food’: which flavours go together and how to read a recipe.”
As well as making nutrition his life’s work, Professor Simpson also has an intense personal passion for food – finding it, catching it, cooking it and eating it. He is a keen fisherman who has written a guidebook for fly fishers and even taught the entomology of trout fishing at the department of continuing education at Oxford. He enjoys baking his own bread and brewing his own beer. While living in Oxford, he and his family would spend their weekends picking mushrooms or exploring the hedgerows to find blackberries and crab-apples to turn into jam.
Using fresh ingredients is an important step towards countering obesity, diabetes and cardiovascular disease, he points out: “The likelihood of you eating a healthy diet is much higher than if you rely on processed food because you know what went into your meal, the origins of those ingredients, and how you’ve treated them.”
But a knowledge of good food has benefits beyond health, he suggests. “We need to understand the ‘language of food’: which flavours go together and how to read a recipe,” he says. “The fact that these skills are becoming increasingly rare in our society should concern us, just like the loss of any language.”
Beyond transforming our understanding of obesity and ageing, Professor Simpson’s research is also providing new insights into how ecosystems and food webs are shaped by the search for nutrition. He is even working with the pet food industry to help design better foods for our companion animals, and with the aquaculture industry to optimise fish feed formulations.
This year his career will pivot in a new direction when he makes his television debut as the presenter of the ABC1 series Great Southern Land. The four-part documentary will look at Australia from an aerial perspective to reveal otherwise hidden patterns, such as the impact of our demand for food and power on the environment. After some initial reluctance (he had to be asked twice), he is looking forward to his reinvention as a high-profile science communicator: “It’s a fantastic chance to share my interest in complex networks with the wider community,” he says.