Did you drink alcohol the night before the test? That would certainly impact trig levels. You might be surprised but brown rice is not as healthy as people think.
You could try basmati, also long grain is a lot better than short grain.
Normal white rice is terrible on the GI index, basmati is a lot better, and if I remember correctly brown rice does not fair well either.
You can try drinking some apple cider after your carb meals, maybe a tablespoons worth mixed with water.
Studies suggest 20-40% lowering effect of the GI.
I went on a test diet where I eliminated carbs from my daily intake except for oats in the morning. after 3 weeks I had a dramatic decrease in ldl and trigs. This diet had a much better positive effect than a low fat diet to reduce cholesterol.