Is it true that if you're healthy and you eat a meal, it shouldn't affect your energy (i.e. make you tired or give you energy)?

What kind of meal? Overindulgence in a fatty meal could make you feel sluggish for a short period. For healthy diet: http://www.choosemyplate.gov/., exercise 30 minutes/day, drink enough water daily so your urine is mostly colorless, have safe sex, no tobacco alcohol weed or street drugs. Get HPV, Flu and Covid vaccines. Wish you good health!

The whole idea of eating is to provide the energy for daily and normal function of every cell and organ in the body. Sure, Food affects one's body energy. Some foods like proteins and fats do not convert to energy as quickly as the Sugars and Carbohydrates do. So while some food can make one 'feel' tired while being digested, others can pump up the energy almost immediately.