Losing fat is a matter of burning more calories that you take in. You can do that a couple different ways: by increasing the amount of time you work out each week, or by increasing your workout-session density—doing more work in the same amount of time.

Since we're all crushed for time, let's look at how to get denser by adding "filler" exercises between sets. These fillers will help you burn fat faster by making your training less efficient. Say what?

No Rest or Little Rest Between Strength Sets

Who in their right mind would want to make their training less efficient, right? Think of it like this: When you know how to do a movement really well, your muscle memory helps you do it more efficiently, so you burn fewer calories. But when you try a new movement, it takes a while to get used to it, and that can burn up a lot more energy.

"Filler" exercises are movements you add between your normal resistance movements to increase density. They come in three basic varieties:

• Level 1 fillers are mobility exercises
• Level 2 fillers are calisthenics and light plyometric movements
• Level 3 fillers are light strength movements

Each level works best when you pair it with the appropriate strength movements. Here are some examples of dense, inefficient workouts to accelerate fat loss.

Level 1 Fillers + Strength Workout

Level 1 exercises are pretty mellow, so you won't need rest periods. Just move back and forth between the fillers and the strength exercises without stopping.

Level 2 Fillers + Strength Workout

After you've been using Level 1 fillers for a month—and maybe done some cardio on your off days—progress to Level 2 calisthenics and light plyos. Fillers at this level are more challenging, so take a 30-second rest before going back to the strength move.

Level 3 Fillers + Strength Workout

Now that you've gone through Levels 1 and 2, up the ante by adding light, timed strength fillers between your sets of heavy strength exercises. Keep some fuel in the tank after the fillers so you can complete the rest of the workout.

Level 3 Fillers + Strength Workout

Notice that Level 2 and 3 fillers work muscle groups that aren't involved in your strength workout. If it's leg day, your fillers should be upper-body movements. If you're training upper body, the fillers should be for legs. The 30-second rest interval done after each superset should also aid with recovery. Just don't let those 30 seconds become a minute.

Keep challenging yourself at this level, but don't finish every set feeling like the grim reaper just tapped you on the shoulder. Once you've hit the eight-week mark at Level 3, return to Level 1 fillers to give yourself a rest.

Use Fillers to Intensify Leg Day

This last workout combines fillers from all three levels, starting with the most difficult. It's designed for an intermediate-to-advanced lifter with good cardiorespiratory fitness. Know your own fitness level, and make changes as necessary.

Test It on Yourself

Increasing your training-session density is a solid, safe, and effective way to improve your fat-loss efforts. If you're new to this technique, start at Level 1 and take your time progressing onward. Make your sessions dense and your workouts inefficient, but pace yourself so you're ready for your next training day. Be consistent with this plan, and you'll be set up for some serious fat loss.