Food comas?

Wondering if food comas are a thing. Before I started losing weight, I would eat a large meal with plenty of flour and sugar and then feel immediately tired afterward. I was always told “it’s a food coma, because the blood from your brain has to go to your stomach to digest all the food you just ate, that’s why you get tired and need a nap after a big meal.”

Is this a real thing or just something someone made up to justify eating a big unhealthy meal?

Wondering because even though I have lost about 45 pounds already with Brooke’s program, I sometimes still get mini “food comas” where I will eat a relatively large meal, eating until I’m about a 3-5 on my hunger scale (tons of veggies, protein, good fats), and occasionally still feel a little tired afterwards. Wondering if this is normal at this point or maybe if my portion sizes are too big?