Does fasting before a blood test for triglycerides make much difference in the results?

Also, what is the recommended diet for high triglycerides (hyperlipidemia)?

Yes. Your blood should be clean for trigs but not for cholesterol.

Triglycerides are a type of fat an ester formed from glycerol and three fatty acid groups. Triglycerides are the main constituents of natural fats and oils, and high concentrations in the blood indicate an elevated risk of stroke. Fasting gives an accurate blood level.The recommended diet is a low fat diet.