There are two ways to understand such hadiths:
1- The hadith is metaphorical, not literal. True believers are those who:
-spend a good portion of the night worshipping Allah
-they cry out of their love and fear of Allah
-They don’t overeat
-They are extremely humble
So this is the message of the hadith.
2- Some scholars take it literally, but they say the hadith is contextual. In those times when poverty was so widespread, the true believers would not eat much because there those who were starving around them.
Now: it’s good to be healthy and strong, but one must not be obsessed with his body image and with his physical strength. Imam Ali (a) would barely eat but he was physically strong. Allah grants believers spiritual strength. So one must be moderate and balanced. Some people eat a lot and spend hours in the gym to burn that and be fit. That’s excessive. One should be moderate.