Cardio can definitely be a tool used to help put you into a caloric deficit. It can be one tool for helping shed body fat; however, it shouldn’t be the first and main focus of your program. Consider it more of an ace card to use than the first tool to implement.
Too Much Cardio
We don’t want to rely too much on cardio. It doesn't send a strong muscle-building signal, and it prioritizes burning muscle over fat. If you are lifting 2-3 times a week, and getting your steps and movement in, then cardio is a great tool to bring in to help hit that step count if you are not able to do it on your own. If you are doing a ton of cardio but not lifting, then I would back off cardio and make sure to include at least 2-3 resistance training days.
Remove Calories First
You can only burn so many calories from a cardio session. A steady-state jog, which is your best bet in terms of intensity, so that you burn more fat than muscle, will only burn around 500-600 calories in an hour. That’s not a lot at all for spending an HOUR on the treadmill. You are better off subtracting 500 calories from your diet first, and not doing cardio yet. This will give you time back, and allow you to focus and keep your energy towards your strength training sessions. Having said that, you need to be at a good place calorie-wise to subtract 500. If you are only eating 1,500 calories right now, 1,000 calories isn’t a healthy place to start a diet. You are better off spending your time building up to 2,000 calories and then dieting.
Sustainability
It’s also hard from a sustainability standpoint, to add so much cardio in. You are better off as mentioned earlier, by increasing your step count. Add 2,000 steps to whatever your current average is. Eventually, you want to work up to 10,000 steps. Increase from there as needed. The benefit of focusing on step count throughout the day is that most people find it a lot easier to find time within their busy days to go for a walk versus going to the gym after work and running for an hour. It’s also more sustainable, as it allows you to make it a lifestyle habit you can keep up with.
Adaptation
When you do too much cardio, your body prioritizes burning muscle over fat. Your body will also get more efficient and burn less calories. Your body is built for survival. It doesn’t know you want to lean out. It just knows it needs to keep you alive. Because of this, it will do whatever it takes to hold onto fat, as fat is a great energy source for your body. Muscle is calorically expensive, so it would rather get rid of that when in starvation mode. The only way to keep your hard-earned muscle, on the other hand, is by making sure you are lifting at least 2-3 times a week.
