The biology of diet: Getting the right food

I am what I eat. Are you?

In his incredibly entertaining book The Body: A Guide for Occupants, Bill Bryson opens the chapter Food, Glorious Food, with a quote from Jean-Anthelme Brillat-Savarin’s 1825 treatise on the mouth and ingestion The Physiology of Taste ‘Tell me what you eat, and I will tell you what you are.’ Overweight.

I have my reasons. Being passionately curious about food and enjoying the experience of eating, sharing, celebrating, and using food to reconcile the conflicts of the day, are some of them. And when I pick up Nathan H. Lents’ latest book Human Errors: A Panorama of Our Glitches, From Pointless Bones to Broken Genes, and read that as humans we have a tendency to gain weight easily and to lose it with great difficulty because this is what made sense in the Pleistocene savannas, I am consoled.

The challenge above them all

We might need to be reminded, then, that, of all the challenges we face in life, which Darwin gently called the ‘hostile forces of nature’, finding food is a daily one. Simply said, there is no survival much less evolution without food because it is diet that either allows or constrains all our other systems of adaptations. 

A plateful of insights

Through its combination of biology and culture, evolutionary psychology offers the ideal platform to organise our understanding of diet, allowing us to explore the utility of food from many perspectives, and providing us with insights into our struggles with food: the genuine needs, the relationship with status, the significance of rituals, the pleasures around dining and wining, and the importance of food in the social fabric of communities; but also the darker side of malnutrition, cravings, addictions, eating disorders, and food-related diseases of the modern age.

Biology matters

The first fact from biology class is that we have what Lents calls ‘a needy diet’. Unlike other animals, our bodies have lost the ability, probably through random gene mutations, to make certain nutrients that are essential for survival. This is the story of some very famous vitamins, amino acids, and metals. It’s not complicated: we either consume them or we die.

Next comes the problem above all others: food selection, or the art of getting food in adequate amounts, without consuming dangerous levels of toxins. Keep in mind, for example, that the human brain is, metabolically speaking, a rather expensive organ to run – it consumes about 20 – 25% of the body’s calories even if it only makes up for 2 – 3% of body weight. And then we have another evolutionary insight: plant toxins are adaptations to defend the plants from being eaten, hurting omnivorous humans in the process.

Tailored design, by nature

It is no wonder then, that pregnancy sickness, the condition in which a woman experiences a heightened sensitivity and a nauseous reaction to particular foods during the first 3 months of pregnancy, is an adaptation that prevents mothers from absorbing teratogens (substances that may cause birth defects via a toxic effect on an embryo or fetus). And yes, you guessed right. Many plants, including the innocent potato and the more sinister eggplant, contain teratogens. Although those who have suffered pregnancy sickness (myself included) would disagree, this is an exquisitely tailored mechanism of adaptation, with the vomiting that is part of the sickness being a sign of health rather than a dysfunction.

It takes much more than a short article for a tour of evolutionary psychological insights into why our brains are not wired for the modern kitchen. We would need to open up about ancestral conflicts, evolved taste preferences, adaptations such as neophobia (children’s aversion to new foods), the emotion of disgust, the marvelous invention of cooking, the human penchant for drinking alcohol, and the controversy surrounding whether it was hunting by men or gathering by women that provided the critical push for evolution.

It often comes down to a question of biology. Like the fact that you cannot fool nature’s design, with its inbuilt controls that allow you to eat according to your hunger and fullness, helping you create that naturally trim body you’ve always dreamed of. Unless you mess with the food; processing it so that its calorific density is abnormally high, triggers our biological survival drive for sweetness, and interferes with the normal functioning of the nutrition and stretch receptors in our gut. This is the message in the video “How to lose weight without losing your mind” by evolutionary psychologist Doug Lisle, author of The Pleasure Trap, in which he explains the scientific principles of satiety and our biological instincts to seek high fat, high sugar foods and to avoid the pain of hunger.

A solution for your hunger

This does not mean that evolutionary psychology holds the magical solutions to all our struggles with diet and the many cases when our delicate relationship with food goes wrong. But it certainly pays to know the truth about our evolutionary history and the knowledge that can guide us to make informed choices about the diet our body needs. Sitting there, among the many diet books, each with their promise for a plan according to blood type, underlying conditions, lifestyle, etc., there should be one that stands out with real benefit, and it is the one about the diet that is right for your human nature.

This article was first published on Times of Malta.

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