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.
Step 3. Add the tuna steaks to the pan once the oil is fully heated and sear for about 2 to 4 minutes per side. Tuna steaks typically are between 1- to 1 1/2-inches thick. Searing the steaks for 2 to 4 minutes leaves the steaks done to rare or medium-rare.For more well-done steaks, add a few more minutes per side, but lower the heat slightly to avoid over-browning the outside.una steaks typically are between 1- to 1 1/2-inches thick. Searing the steaks for 2 to 4 minutes leaves the steaks done to rare or medium-rare. For more well-done steaks, add a few more minutes per side, but lower the heat slightly to avoid over-browning the outside.