380 calories for one piece of fish sounds reasonable until you remember that patin is a naturally fatty river fish, and then you pile on tempoyak (fermented durian, which is basically concentrated durian fat and sugar) plus coconut milk in the gravy. The 90 calories from coconut milk alone and 68 from the tempoyak paste add up fast. To be honest, the numbers here are a ballpark estimate because solid nutritional data for this dish is basically nonexistent. Patin's fat content varies depending on the fish size and season, and every mak cik recipes the tempoyak ratio differently. Treat 380 calories as a reasonable middle-ground guess, not a lab result.
What actually moves the number is how much gravy ends up on your plate. That thick, lemak gravy is where most of the calories hide. If you ask for less gravy, or go with the tanpa santan version (broth-based, no coconut milk), you can bring it down to around 250 calories. The heavy gulai-style version with a thick coconut curry base goes up to about 460 calories for the same size piece. The fish itself is only around 175 calories for 150g, so the protein is actually decent, bro. If you pair one piece with a smaller portion of rice and load up on vegetables instead, the full meal can stay under 600 calories without feeling like punishment.