The Ancient Greeks and Romans already understood that food and physical exercise influence our health and our weight. The Greek ‘diatia’ (from which the word ‘diet’ is derived) referred to a whole way of living focused on self-control and eating in moderation. With Christian asceticism, this moderation was translated into self-denial, whereby the body was seen as an obstacle to the elevation of the soul, as with the example of Saint Anthony in the late 3rd century CE. The sin of gluttony continues to haunt the Christian world today.
In 1474, the Italian humanist Bartolomeo Sacchi, aka Il Platina, wrote the first bestselling diet book. Advances in printing techniques meant that his De honesta voluptate e valetudine was read throughout Europe, and high society became obsessed with his recommendations regarding the relationship between gastronomic pleasure (voluptate) and health (valetudine). However, it is How to Live One Hundred Years – Discourses on the Sober Life (1558) by Alvise (Luigi) Cornaro that continues to be cited today. After realising the risks he was taking with his self-indulgent lifestyle, this Venetian aristocrat adopted a frugal diet and lived to become a centenarian. His book makes reference to the ancient writers and thus revives the Ancient Greek principles of moderation to show that a healthy lifestyle starts with a healthy diet.
Scientific advances, notably in medicine, led to discoveries (proteins, carbohydrates, lipids, vitamins, etc.) that altered our perception not only of the human body but also of what we eat. The 20th century then saw the emergence of a plethora of diets that focused on these compounds and their energetic properties. In 1918, Lulu Hunt Peters published Diet & Health: With Key to the Calories. She urged her female readers to consider food in terms of calories and not to consume more than 1200 a day (to put this in perspective, the consensus today is for 1600 to 2500 kcal a day, depending on age, physical activity and health). She paved the way for other methods to lose weight, such as the Weight Watchers diet that allocates points to foodstuffs according to their calorie and nutritional content. Some diets advocate the consumption of particular foodstuffs for the nutrients they may or may not contain. As an example, in gluten-free diets, the Atkins diet of the 1970s or the Dukan diet of the 2000s, it is the nutrient that counts and the form it takes is of secondary importance. Other diets involve abstinence from certain foodstuffs on ethical principles: Veganism goes far beyond a simple refusal to eat any products derived from animals and makes a plant-based diet a real lifestyle choice.