For decades, nutrition counseling in diabetes care has focused primarily on one question: What should patients eat? But a growing body of evidence suggests another question may be clinically important as well: When should patients eat?
Human metabolism follows a circadian rhythm that influences insulin sensitivity, glucose tolerance, beta-cell responsiveness, and energy metabolism across the day. In the morning, metabolic efficiency is generally higher. As the day progresses, glucose tolerance declines and postprandial responses often worsen.
Yet, many patients consume their largest meals in the evening or eat across prolonged daily time windows extending from early morning into late night. From a circadian perspective, this pattern may create a mismatch between food intake and underlying metabolic biology.
Accumulating evidence suggests this mismatch matters.
Controlled feeding studies have demonstrated that identical meals consumed earlier in the day often produce lower postprandial glucose excursions compared with evening intake. Late eating has been associated with impaired glycemic control, increased insulin resistance, and higher cardiometabolic risk.
