Michael Pollan opens In Defense of Food with his now-famous, deliberately concise summary of the book's entire core argument: "Eat food. Not too much. Mostly plants." — using this memorable, seven-word distillation to establish his foundational thesis that genuine nutritional wisdom, obscured by considerable modern nutritional confusion and marketing, can actually be expressed quite simply.

How Pollan develops this foundational, concise thesis:

• "Eat food" specifically distinguishes genuine whole foods from the highly processed, industrially-manufactured food-like products Pollan argues have increasingly displaced genuine food within contemporary diets, despite these products' technical edibility and often extensive nutritional marketing claims
• "Not too much" addresses portion and quantity considerations, connecting to broader themes regarding modern eating patterns' departure from more traditional, typically smaller portion patterns
• "Mostly plants" reflects Pollan's synthesis of nutritional research generally supporting predominantly plant-based dietary patterns, while not requiring complete elimination of animal products entirely

This foundational, deliberately memorable thesis sets up the book's overall project: examining why contemporary nutritional understanding has become so confused despite, or Pollan argues partly because of, extensive scientific and marketing attention, while defending this simpler, more traditional food-based wisdom against this confusion.