Which muscles should I train in order to burn more fat?

The larger muscles are the ones that burn the most calories.  So you should always train back and legs.  Most people like to train chest and arms.  If you have growth in those muscles you will continue to burn calories

If you want to burn more calories in a shorter amount of time, select exercises that utilize multiple joints and larger muscles such as the legs and back. A good example of a full body exercise is the squat to overhead raise. With this exercise, you’re using all the large muscles in your body, and even some of the smaller ones.

To perform a medicine ball squat to overhead raise, grab a set medicine ball and find some open space. Place your feet roughly shoulder width apart and hold the ball just under your chest slightly in front of you. Keeping your stomach and glutes tight, slowly lower yourself through your knees as if you’re going to sit in a chair. Don’t allow your knees to wobble by keeping your glutes, thighs, and stomach tight as you’re lowering. Once at the bottom, hold for a second, and then slowly come back up pushing through your feet and extending your knees. As you reach the top of the squat, press the medicine ball  straight up, and over your head. Bring it back down to starting position and repeat. Perform the desired amount of repetitions and sets.

You should focus on training all muscles for total body health, but the larger muscles will burn the most calories to help you lose more body fat. Those muscles include the legs, back, chest and core. I like to include multi-join movements in all my workouts. If I work my arms then I do a squat at the same time. I also recommend participating in other total body movements like lunges with bicep curls or push ups. Building those big muscle groups will also enable you to burn more calories at rest.

Well, the concept of burning fat can be very complex or we can keep it pretty simple. An easy way to think of it is to work as hard as you can for as long as you can. In this case, the bigger the better! Do movements that use the large muscles of the hips, buttocks, legs and trunk. A few other things to keep in mind make it locomotor if you can. In other words, make it move. Walking lunges done even without any weights, will give you better practical results than sitting stationary on a machine doing leg extensions. Also, multi-joint exercises are more effective than single joint exercises. In other words, instead of standing still doing a bi-cep curl, try doing a curl while doing a squat. The more muscles and joints moving together, the better.  Along with using more energy (calories) they require balance and concentration, which also adds value to your workout!

Training your larger muscle groups like legs, your upper body and abs burn more than training smaller muscles like biceps. You can train these muscles using standard body weight exercises like squats, push ups and chin ups. Of course you should weight train your entire body so you look balanced. The more fat free mass or muscle you have over all will cause you to burn more calories as a whole. Every pound of muscle you add will burn an additional 50 calories so put on 5 pounds of muscle and burn an additional 500 calories a day, and look good doing it.