Then, you need to be strength training.
It’s as simple as that. And it really can be that simple.
The key is to do the strength training first so by the time you’re into your cardio your burning fat from your reserves, not just the cereal you ate for breakfast.
Aim for about 20-30 minutes of strength training followed by 20-30 minutes of cardio.
To really amp up your fat burning potential, do strength training circuits and add intervals to your cardio mix.
For instance, for your strength training cardio, hit your biceps, then your triceps, then your legs and possibly even your abs. Aim for 2-3 different circuits in a strength workout.
For your cardio, whether on a bike, the stairclimber or the treadmill, work periods of high intensity in with your otherwise moderate intensity workout. For instance, work at a pace you would be able to maintain for the duration of your workout (could talk a bit, RPE 5-7), then amp up to a pace you can only maintain for a minute (no talking, RPE 7-9).
Your intervals should be 2-4 minutes moderate, 30 seconds – 1 minute intense. Repeat at least 4 times up to 30 minutes total of cardio.