Fat burn HIIT

I use Fitness Blender. The "HIIT" (it's really more interval training but HIIT is the trendy buzzword) is cardio and being bodyweight is good for overall conditioning but no, it will not help you build muscle. Add their strength training videos into your training and you have muscle retention/gain.

Generally, doing cardio burns calories without building muscle. Doing cardio consistently and often will cause your heart to reconfigure itself to be more efficient at meeting your needs during cardio. This is how 'doing cardio' improves all your cardiovascular measures. Blood pressure goes down. Triglycerides go down. Resting heart rate goes down. These are all great and good outcomes, but they are not building up muscle. Muscle, conceptually, is protein you've eaten which your body has allocated to do the things you do. In a calorie deficit, you run the risk of neglecting to eat enough protein. Your body still has the protein you've eaten and still will allocate it to do the things you do. If it needs to take some muscle tissue and convert it to amino acids to use in some other more important metabolic activity, it will. In fact, even if you eat all the protein you should, your weight loss will still be the losing of both fat and muscle.

What to do?

Your body, as I said, allocates the protein you've eaten to do the things you do. If the things you do include picking up heavy things, your body will allocate protein to the muscles which pick up those heavy things. Of course, that raises your protein needs and you start to discover the well-documented physiology science of protein consumption, structured lifting programs, and all that. That's part of your journey of learning about your health.

For now, though, be aware that cardio is good, but it isn't building muscle. There is a way to build muscle, but it isn't cardio.