From jungle to laboratory and back to our own kitchens, David Raubenheimer and Stephen Simpson’s new book explores how and why we eat, how appetites are fed and regulated—and how, in the end, it all comes back to five appetites.

Having studied appetite in animals over two decades, and transforming the science of nutrition with their findings, Professors David Raubenheimer and Stephen Simpson from the University of Sydney’s Charles Perkins Centre and School of Life and Environmental Sciences are leaders in the field of nutritional ecology and obesity.

Their new book Eat Like The Animals reveals the reasons a baboon, a cat and a locust instinctively know exactly what to eat for balanced nutrition, and yet we humans can’t seem to figure it out.

The surprising role of appetite

“It all comes down to the essential role of appetite to communicate the body’s needs to the brain,” says Professor Raubenheimer, the University’s Leonard P Ullmann Chair in Nutritional Ecology.

“Animals possess five appetites—for protein, carbohydrate, fat, salt and calcium.

“In natural food environments these appetites cooperate to help animals choose a balanced diet. Humans have this ability too, but the modern food environment is so altered that our appetites can no longer work together. Rather, they compete, each vying for its own nutrient. It is this competition that causes us to over-eat fats and carbs, leading to obesity and the serious diseases that come with it.

“Surprisingly, we overeat fats and carbs not because the appetites for these nutrients are stronger, but because the appetite for protein is strongest of all! If protein is diluted in the food supply, we overeat until we satisfy our protein appetite. On high-protein diets, the protein appetite will be satisfied sooner—when fewer total calories have been eaten. This is what we call the Protein Leverage effect.

“But more protein is not necessarily better. Eating too much protein switches on biological processes that hasten aging and shorten lives.”

When food comes from factories rather than fields

Professor Simpson, the Academic Director of the Charles Perkins Centre, describes how our capacity to balance our nutrition has become seriously impaired due to the industrialization of the food system.

“We have made low-protein processed foods taste unnaturally good,” he says.

“We’ve diluted protein in the food supply with ultra-processed fats and carbs. We’ve also disconnected the brake on our appetite systems by decreasing dietary fiber. Perfect for getting us to eat and buy more but devastating for our health. Food cultures globally have been changed by aggressive marketing of these products.

“A pretty depressing story—but it’s not all doom and gloom—you can reinstate your innate nutritional wisdom by taking charge of your food environment.”

What the animals have taught us about healthy eating

The authors have some tips for taking charge of your food environment and helping your appetite to work for you, based on their take on the scientific evidence as informed by their own research.

1. Surround yourself with whole foods

“Surround yourself with whole foods such as nuts, fruits, vegetables, healthy oils, unrefined grains, pulses and moderate amounts of quality meats if you wish. Avoid meals and snacks that are factory-produced, or buy them sparingly,” says Professor Raubenheimer.

“That way, we can expose the amazing appetite systems we share with other species to a food environment in which they are able to work their magic and lead us to a balanced diet.

“Let your brain ensure that your pantry and fridge are stocked with good, wholesome foods; then let your appetites do the rest,” he adds.

2. Aim for balance

“Ultimately, there are endless ways to achieve a nutritionally balanced diet,” says Professor Simpson.

“Various nutritional philosophies slugging it out today can provide healthy eating or can be misused to do the opposite.

“What they all have in common, is reducing or cutting out highly processed foods, rich in sugar, fat and salt and poor in fiber and nutrients

“Unless there are specific medical reasons, you don’t need to cut out any food group or eat things that you don’t like, or that are not appropriate to your food culture. It’s just an issue of proportions.”

3. Make it a habit

Professor Raubenheimer adds that before long, eating an enjoyable healthy diet will become automatic.

“It’s like learning a sport, to play a musical instrument, or to drive an automobile: at first it takes concentration, consciously applying rules, rehearsing them, and unlearning bad habits. And then it becomes second nature,” he says.

“Or, in the case of healthy diets, perhaps we should consider this first nature: creatures from slime molds to baboons have been doing it for millions of years before numbers, formulas, sports, music, and automobiles were even invented.”

Rachel Fergus, University of Sydney