In Chapter 14, Attia underscores that we know very little about nutrition and diet:

Nutrition is relatively simple, actually. It boils down to a few basic rules: don’t eat too many calories, or too few; consume sufficient protein and essential fats; obtain the vitamins and minerals you need; and avoid pathogens like E. coli and toxins like mercury or lead. Beyond that, we know relatively little with complete certainty (296).

In fact, he does not believe that nutrition can improve healthspan and lifespan in the same way as exercise (which goes against conventional wisdom). Rather than using the term “diet,” he prefers the term “nutritional biochemistry” or Nutrition 3.0, which places discussions about nutrition “back into the realm of science” (294).

Attia argues that nutrition research is poor quality. There are two types of nutrition research. The first is epidemiology, or when researchers gather data from a large group of people and extrapolate the results to the population level. Attia takes issue with epidemiology for two reasons. The first is that epidemiology cannot distinguish between correlation and causation. Correlation is when there is a statistical association between variables.