Neutral fat

I got a near-clean bill of health at medical check-up. I said "near" because a value of my "neutral fat(中性脂肪)" in my blood is a bit over the limit. The doctor suggested more exercise.
"I think I am doing enough exercise for may age, because I jog a lot." Said I.
"hmmmm, well then it might come from your constitution." said the doc.
Although I had not run for 3 weeks since I hurt my back and caught a bad cold before the medical checkup, I was still confident that I do exercise more than average.
"Constitutional" is a convenient word. You know, if a doctor cannot explain the cause of your physical problem he says "it might be constitutional". "Constitutional" means something you are given by nature. You can't change it basically but it is also something you can control with the help from medical care or by your own efforts.
The word "stress" is used as well in the same context for a doctor to avoid answering "I have no idea about the cause of your illness." Instead he would say "It might be from your stress." When my wife was diagnosed of Meniere's disease, she asked the doctor the cause. "Perhaps stress." He answered. Although she said
"I do not feel even a nano bit of stress in my daily life",
the doctor insisted
"You must have stress deep down inside even if yourself might not be aware of it."
This conversation itself was stressful, she recalled.
There are still tons of diseases, the cause of which we do not know. If you don't know it, don't pretend to know it by bringing up an authentic-looking words.