It appears, from doing a little reading on the subject, that triglycerides are created when there are extra calories taken in that are not needed at the moment. They are a source of energy for the body, but high levels are an indicator of heart disease as they are a type of fat that flows in the bloodstream, and fat cannot be disolved in the bloodstream. Carbs and fats more easily produce triglycerides because they are more easily digested compared with proteins, and insulin resistance (a common problem with those who are obese) also correlates with higher triglyceride levels.
It looks to me like triglycerides, as the standard pathway by which excess calories are stored and then retrieved for later use, are a normal part of the metabolic process, and the reason doctors pay attention to triglycerides is just because of the correlation between higher levels and heart disease.
Current PRs at 242- 495, 345, 585, 1425