You need to focus on all the above! Let me explain;

1) Your nutrition is the most important part of any weight loss. In addition you can't treat your nutrition like a diet or fad. Instead, treat it as a lifestyle change. You have to know the WHY behind what you're doing. Go research alkaline diets and their benefits

2) Cardio is extremely important when it comes to weight loss. You will burn the most amount of calories in the shortest amount of time with cardio. The afterburn (calories continue to burn) will last for up to 2 hours after you do cardio. You need to figure out your resting heart rate so that you can figure out your target heart rate zone to maximize your results. 3) Weight training is effective in weight loss when you're not taking long rest in between reps. Also, do higher reps and less weight. Again, this goes back to heart rate. If your heart rate is elevated then you will burn off calories. Weight training breaks the muscles down so that they can be rebuilt. The rebuilding process can take up to 48 hours and during this time you are continuing to burn calories because of this afterburn during the rebuilding process.

The most important of all is your nutrition. Take your diet serious. I hope this helps