The first lady, Michelle Obama, on Thursday relegated the government’s well-known food pyramid to the sands of history, unveiling a new, simpler image of a plate divided into basic food groups.

The new design, called MyPlate, was conceived as a crucial part of Mrs. Obama’s campaign against obesity, designed to remind consumers about the basics of a healthful diet.

The plate is split into four sections, for fruit, vegetables, grains and protein. A smaller circle sits beside it for dairy products.