Nutrition, Diet & Fasting - Diets
The paleo diet
A diet built on a story about the past that the evidence does not really support - and which, despite that, tends to work reasonably well for reasons that have nothing to do with the story.
The paleo diet excludes grains, legumes, dairy, refined sugar and processed foods, on the premise that human beings are adapted to what was eaten before agriculture. It is one of the more coherent popular diets in practice, and one of the weakest in its stated rationale. Both of those things are worth explaining, because the gap between them is a useful lesson in itself.
The premise, examined
There was no single palaeolithic diet. What hunter-gatherers ate varied enormously by latitude, season and what was available - from heavily plant-based to almost entirely animal-based - so "eating as our ancestors did" does not specify a menu. Studied contemporary hunter-gatherer groups eat very differently from one another and often eat foods the diet excludes, including tubers, wild grains and honey.
The claim that humans have not adapted since agriculture is also not right. Lactase persistence - the ability to digest milk into adulthood - spread through several populations in the last few thousand years and is one of the clearest examples of recent human selection there is. Copy number variation in the gene for the starch-digesting enzyme amylase varies with ancestral starch intake. Adaptation did not stop.
And almost nothing in a modern supermarket resembles its wild ancestor. Domesticated fruit is far sweeter and larger, modern meat is far fattier, and the vegetables involved were selectively bred into existence. A paleo diet is a modern diet with a historical justification, not a reconstruction.
Why it works anyway
Because the rules, whatever their stated reason, remove almost all ultra-processed food and almost all added sugar, and raise protein and vegetable intake. That is a combination with real evidence behind it, as the ultra-processed food lesson sets out. Small and medium-sized randomised trials of paleo-style diets have generally reported improvements in weight, waist circumference, blood pressure and some metabolic markers - typically over weeks to months, often against fairly weak comparison diets, and usually without demonstrating an advantage over other whole-food diets tested properly against them.
This is worth naming clearly, because it is the same pattern that runs through this whole classroom: a diet's results and a diet's explanation for its results are separate things, and can be judged separately. Paleo has decent outcomes and a poor rationale. It would still work if you deleted the story.
Where the evidence stops
Trials are mostly short, small, and compared against a control that was not equally well designed - which inflates the apparent advantage. There is no long-term outcome data. And the exclusions have costs worth counting: legumes and whole grains are among the most consistently health-associated foods in the observational literature, and excluding dairy removes a convenient calcium source that then has to come from somewhere.
Educational content only and not medical advice or a recommendation to follow any diet.
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Educational content only. Not medical advice, diagnosis or treatment. Always consult a qualified healthcare professional before changing your health regimen.
