It’s really common in the first few weeks, particularly if you’re sensitive to GLP1s. I was wiped out the first couple of months, but it did get better.
I’m 2 years into Mounjaro now and after a recent low end HbA1c blood test, I’ve bought and been wearing a CGM (continuous glucose monitor) this week and eating normally to see what’s happening when I get that wiped out want to go to bed feeling after a meal, and I’ve seen that sometimes after eating I get quite a sharp glucose drop.
I injected Saturday morning and had an Indian curry (the works, high fat) Saturday night, and my CGM very briefly dropped into hypo territory (3.3 mmol/L), which left me absolutely wiped out, blurry/heavy eyed could have done with a nap. for a few hours afterwards.
Other meals such as salmon and green veg (high protein, very low carbs) see glucose dips, lunch such as a cheese and ham toastie (higher carbs) showed a steady rise and fall.
I’m wondering whether something similar could be contributing to that sudden post meal exhaustion for you. GLP1s alter gastric emptying and glucose regulation, high protein or high fat meals can slow gastric emptying even further, meaning the carbs are released more slowly, while insulin is still being released in response to the meal potentially causing the dip in glucose.
Smaller, more balanced meals with protein, fibre and some carbs might be worth trying while your body adjusts.