1 Add time each week to work your way up to 30 to 45 minutes of continuous exercise. 2  As you get stronger, try interval training once a week to help boost endurance and burn more calories.  Work your way up to 5 to 6 days of cardio and try to vary what you do and how hard you work.
To achieve a sear on the outside and keep it rare inside, place the tuna on the skillet or grill and let it sear for two minutes on the first side. Flip the tuna and let it cook for another two minutes, then remove it from the heat. Watch the tuna as it cooks to make sure you don't overcook it.
1 Preheat grill for high heat. 2  Lightly oil grill grate. 3  Cook the tuna steaks for 5 to 6 minutes, then turn and baste with the marinade. 4  Cook for an additional 5 minutes, or to desired doneness.