The word dessert has come to mean a refreshment served after a meal. For this reason, the meal could be breakfast, lunch, or dinner. If you go to any restaurant and order a meal, the serving staff always ask patrons whether they care for a dessert after the main meal has been eaten. Desserts are often eaten before dinner as a part of other meals.
Then, there is the debate over whether dessert should be eaten right before dinner. Typically, no, diners usually wait until dinner has been eaten to eat dessert.
However countless culinary experts and consumers with a sweet tooth have espoused the virtues of eating dessert before diner. However, you would be hard pressed to find a nutritionist or dietician that will advise you load up on sugar and carbs before eating a healthy meal. While it can definitely ruin an appetite, plenty of people have eaten dessert before their main meal.