In your article you report, “Every 4 years, each volunteer completed a questionnaire about his body weight and dietary habits.” Any dieter knows that it is next to impossible to remember what one has eaten 4 days ago. Any more details on how the data was acquired and validated?

Ivan Mann
Hoover, Ala.

Volunteers were asked to state the frequency of their consumption of various foods over the past year. They had nine choices for each answer, from “never” to “at least 6 times per day.” —B. Harder

From the Nature Index

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