I am about to turn 70 Male. Have been experiencing fatigue the past 4 weeks. Since last November, have been running 3-4 miles about 5 times per week. Have modified my died to salads and vegetables, little meat. And I am gaining weight instead of losing it in spite of rigorous exercise. No other health problems. Recent blood panels are normal. My cardiologist says my recent EKG revealed a problem , but nuclear stress test revealed nothing. Why am I gaining weight and feeling fatigued?