Mon, Jun-22-20, 00:46
Eat Like the Animals: What Nature Teaches Us About Healthy Eating
You’ve got five appetites — not just one
The trick to satisfying them is to eat like an orangutan, not a labrador, says Michael Odell
For dinner last night Stephen J Simpson ate a vegetarian feast of chickpeas and aubergine followed by a triangle of Shropshire blue cheese and a pear. Meanwhile his friend and colleague David Raubenheimer ate smoked salmon with gazpacho soup and a slice of homemade seed bread.
“You caught us on a good night,” Simpson says. “It was healthy and filling.”
The most striking thing is that both men knew when to stop eating. Simpson, a professor at the School of Life and Environmental Sciences at the University of Sydney, and Raubenheimer, a professor of nutritional ecology, also at Sydney, are renowned nutritional scientists. They have spent more than 30 years trying to understand appetite in animals as well as humans, and their new book, Eat Like the Animals: What Nature Teaches Us about Healthy Eating, presents us with a revelation: humans don’t have just one appetite, we have five.
Which is to say, naturally, we are compelled to consume the following five nutrients in precise quantities: protein, carbohydrates, fats, sodium and calcium. Satisfying these urges — these five appetites — without consuming too many calories is, they argue, key to good health.
“For many years appetite was considered a one-dimensional thing,” Simpson says. “But the more we looked at the eating habits of animals, from locusts to mice and spiders, we realised most animals know how to seek out a nutritionally balanced diet of five elements by pure instinct.”
Raubenheimer and Simpson began with painstaking research into the eating habits of locusts. And I mean painstaking. They crawled about in the scrub following individual locusts, recording what they ate. Simpson even gave them Vaseline enemas to see if the stretch receptors in their rectums affected their meal size.
“We were pretty hands-on,” he says, sounding a bit weary.
Their discovery? Locusts do not, as is commonly supposed, omnivorously consume everything in their path. They want protein and they want it in quite exact amounts.
“Protein is the first and pre-eminent of the five appetites,” says Simpson. “And once locusts have found a healthy and plentiful source of protein, the other two essential macronutrients (carbohydrate and fats) as well as the two essential micronutrients (sodium and calcium) are quite often present too.”
More astonishing is that Simpson and Raubenheimer found the same ability to instinctively eat a nutritionally balanced diet in mice, spiders, baboons and orangutans. And in theory, humans should be the same. Our bodies have certainly evolved a clever way of ensuring that our five appetites are met. As Simpson and Raubenheimer write, the three macronutrients plus two critically important micronutrients “correspond precisely to the same nutrients that we are able to taste in foods. A most elegant solution to an otherwise impossible challenge. Our appetites have evolved to target specific flavours and guide us to eat only the things we need to survive.”
But why these particular five? Simpson and Raubenheimer give several reasons: they are needed in the diet at precise levels; foods vary in their concentrations of these nutrients; and some of these nutrients were once so rare that we needed what they describe as a “dedicated biological machinery” to seek them out. This is why gorillas eat tree bark to get enough salt and pandas migrate to get enough calcium. Finally, if we satisfy these five appetites, we should automatically get enough of all the other essential nutrients we need.
There is a caveat. If we are so well evolved, our five appetites so tightly honed, how can you explain rocketing global indices for obesity, heart disease and type 2 diabetes? That is because, in nutritional terms, humans have lost their way.
Raubenheimer and Simpson put forward what they call the protein leverage hypothesis. As per the five appetites, like most animals, humans have a daily protein target (after all it is specifically protein that allows us, through its nitrogen content, to replicate DNA and repair damaged tissue). We should eat just the right amount — not too much or too little.
However, the industrialisation of food has led to a proliferation of what the authors call “decoy protein products”. Crisps, biscuits and plenty of other processed foods dilute expensive-to-produce protein with unnecessary sugars, carbohydrates and fats. We crave our daily protein and ingest vast quantities of unnecessary calories trying to get it.
“Ultra-processed foods are skilfully designed to smell and taste like they are protein-rich, but they don’t give your body what it wants,” Simpson says.
There are other factors interrupting our search for protein. We have reduced the protein content of plants through carbon dioxide emissions and stopped eating roughage that makes us feel full.
The authors pose a stark question: if an orangutan can eat healthily without reading a diet book or knuckle-dragging its way to a Weight Watchers meeting then why on earth can’t we? Raubenheimer and Simpson insist we can — if we get back in touch with our five appetites.
“We don’t believe it’s complicated,” says raubenheimer. “You won’t need special glucose monitors and specialised data collection as some nutritionists suggest. You’ll need to do a basic calculation, shop for the right foods but then, just listen to your appetite.”
How to satisfy your five appetites
You have five appetites — your body wants protein, carbohydrates and fats plus a range of micronutrients, the most important of which are sodium and calcium. However protein is key. But how much to eat?
Use the Harris Benedict formula to work out your metabolic rate (an online calculator will help you do this). Enter your weight, height, sex, age and activity levels and the formula will give you your daily calorie needs.
About 15 per cent of this daily calorie intake should come from protein. If your daily calorie needs are 2,000 calories per day then 15 per cent of that is 300 calories. One gram of protein contains 4Kcal of energy, so you will need 75g of protein a day.
That’s about 330g of lean meat or fish. Or about 875g of chickpeas, lentils or kidney beans.
“The figure changes according to sex and activity levels and age, but that is the cornerstone of your diet,” Simpson says.
But don’t have too much
One of Raubenheimer and Simpson’s most compelling revelations is the role of protein in the struggle between the “longevity pathway” and the “growth and reproduction pathway”. These are two separate biochemical pathways that have been shown to lead to different life outcomes in humans as well as mice and other animals. Follow the first and you will live a long time. Follow the second and you will bear many children, but die young.
These pathways exist in opposition to each other and either one can be ascendant, depending on how much protein you eat.
Eat a lot of protein and your body registers that there is plentiful food and begins to create more tissue and prepare your body for reproduction. So yes, eat cheese, eggs and steak and surpass your “protein target” and you will have lots of children. You are on the “growth and reproduction pathway”, but the downside is that in this mode the body tends to downgrade cell and DNA repair. You will lead a shorter life.
“This is how we lived 200 years ago,” Raubenheimer says. “People had 14 offspring, but died young.”
However, stick to a lower protein diet and this will trigger the “longevity pathway”. Your body registers there is less food around and begins to prioritise repair and maintenance. This is the basis of the 5:2 diet and many other “intermittent fasting diets” in which periods of fasting trigger just such body preservation responses.
“Of course the sensible thing to do is regulate your protein intake to suit the stage you are in life,” Raubenheimer says.
Choose your sources wisely
It all sounds pretty straightforward. Eat your daily protein allowance and no more. But you have to be careful where you get it from. If you are a 40-year-old woman and you have calculated your daily protein target as 70g of protein, you could get that from 680g of yoghurt or cottage cheese. Or . . . 1.4kg of doughnuts.
“That, I am afraid, is the story of the global obesity crisis in a nutshell,” Simpson says. “People too often are trying to find the protein their bodies rightly crave by turning to very cleverly designed foods which taste and feel like they are satisfying you hunger, but which are delivering a calorie bomb instead.”
Marginal differences make you fat
Your protein target is about 15 per cent. But say you are having a busy time at work or travelling and so shopping or cooking healthily becomes difficult. You are snacking on junk food, which means the percentage of your diet that is protein slips to 13 per cent. Doesn’t sound much. But missing your full quota of protein might set off a disastrous chain of events.
Raubenheimer and Simpson offer this scenario in the case study of “Mary”. The proportion of her daily diet that is protein drops to 13 per cent and so she has to consume an extra 290Kcal to meet her protein target. That’s a chocolate bar a day. Within two years she will put on 26lb. Heavier people require more fuel so her protein target rises progressively.
Never burn your furniture to keep the house warm
When you’ve eaten a meal your body registers heightened blood sugar and secretes insulin, which signals that you have glucose to burn for energy.
However, if you overeat, your body will eventually be unable to process insulin. Your liver unnecessarily starts to burn muscle to make glucose, which then requires more protein. Raubenheimer and Simpson compare this needless burning and overconsumption of protein to “burning the furniture in your house to keep it warm”.
“It should never come to that. And there is worse news I’m afraid,” Raubenheimer adds. “There is evidence that altered dietary habits can be passed on epigenetically to babies. You are setting your baby on a health trajectory before it’s even born.”
And just for clarity’s sake, you should never burn your furniture to keep the house warm either.
Eat like the animals . . . but not dogs
“We found the ability to eat healthily by instinct throughout the animal world. But people often say, ‘What about my labrador?’ and it’s a fair question. Appetites evolve. We have domesticated dogs, breeding out their hunting instincts to protect ourselves and livestock. They posed a threat in a way that cats didn’t. We still encourage cats to hunt mice and so they retain a sense of their instinctive nutritional needs. Dogs have got used to sitting by the table for scraps and even evolved the ability to digest foods that they were once were unable to, like starch through the enzyme amylase. I’m afraid some labradors have become disconnected from their instinctive dietary needs, just as we have.”
Eat Like The Animals by David Raubenheimer and Stephen J Simpson is published by William Collins
A New Scientist Best Book of 2020
How is it that a baboon and a blob of slime mould instinctively know what to eat for optimal health, balancing their protein, fat and carb intake in perfect proportions?
In new, groundbreaking research that is transforming our understanding of nutrition, animals from locusts to lions and yes, humans too, demonstrate the remarkable science behind appetite.
Appetite communicates the body's nutritional needs to the brain, and eating in accordance with your body's demands, like the animals, should ensure optimal health, but the modern fast food world wreaks havoc on this evolutionarily honed system.
In several landmark studies, Raubenheimer and Simpson prove that appetite can be hacked – we can eat for optimal health, for increased fertility or for a longer lifespan. Understanding the science of the appetite offers tremendous power in shaping our bodies and controlling our lives.
Last edited by Demi : Mon, Jun-22-20 at 01:06.