Cardio has this strange over-importance among most people. You always hear the layman talk about needing to excercise to lose weight and they don’t really expect to diet. You can do all the cardio in the world, but if you eat enough to overcompensate all the cardio you won’t lose fat. Diet is most important. Cardio is just a tool to add. If your like me who struggles to gain muscle, then you carry more about how much muscle it might burn off, rather than how much it aids in fat loss.
I think how much cardio effects you depends on a couple of factors. It matters what type of cardio you are doing. low intensity cardio like fast walking isn’t really going to cause you to lose muscle as long as you eat a meal beforehand. Low intensity cardio doesn’t really spike the cortisol levels high short term either, unless you do it for a very long time. Keep it under 45 minutes. It also depends on the equipment that you are using so make sure to buy premium gym equipment.
The only time your muscle will be in jeapordy on low intensity cardio will be if you do it in the morning on an empty stomach. Yes you’ll get more mobilized fat in the morning, but you’ll be eating away your muscle a lot easier cause your insulin levels are low and glycogen is depleted after sleep. Those doing cardio in the morning on an empty stomach are sacrificing a little more muscle for the extra fat loss.
If you do HIIT that is very stressful on the body. Cortisol spikes very high quickly due to the intensity. Its effect on your metabolism is equal to a short weight training session. Doing weight training together with HIIT cardio 3 times a week can have a serious effect on your recovery abilities and cause high elevated cortisol levels. HIIT cardio isn’t recommended for most because it will lead to overtraining for many quickly because its hard for your body to keep up with HIIT cardio and weight training while dieting too. Dieting and weight training are almost too much as it is for the body to handle.
HIIT cardio has a good effect on fat loss like weight training in regards to releasing growth hormone and affecting metabolism. Its also good at burning subcutaneous fat specifically. However, you will sacrifice a little extra muscle to get that extra fat loss. I would advise HIIT cardio only for someone who has good genetics and can handle this type of cardio and has some stubborn fat to get off, only after they have been dieting for many months. Most people won’t ever need to utilize HIIT cardio you can use diet manipulation to get where you need to as long as you slowly cut your calories as your metabolism slows down so you keep losing steadily every week..