диета

In a sentence

• Я начал новую диету, чтобы улучшить своё здоровье.

  I started a new diet to improve my health.

  Here, 'диета' is used to mean a structured plan of eating aimed at achieving a health-related goal.

• После праздников многие задумываются о диете.

  After the holidays, many people think about dieting.

  Here, 'диете' (prepositional case of 'диета') implies the general concept of regulating one's diet, often for health or weight management.

• Доктор рекомендовал специальную диету для восстановления.

  The doctor recommended a special diet for recovery.

  Here, 'диету' (accusative case of 'диета') refers to a medically prescribed set of dietary rules for health improvement.