Exercise 20 minutes, or 40 minutes?

How long should we do cardio to lose more body fat?

I don’t remember exact sources but I heard quite a few times that longer cardio with low intensity is better than short cardio with high intensity because low intensity cardio workout uses mainly body fat as fuel while high intensity cardio workout uses more carbohydrate. It is also said that body fat starts to burn when you are into cardio exercise at least 30 minutes.

I decided to be more creative and make my own theory that we should do a cardio workout at least 40 minutes. I thought that that way we would keep burning fat at least for 10 minute after the 30 minute turn point. Not only I have been trying it myself but also I strongly wanted my husband to follow it.

He didn’t seem to be too enthusiastic about my suggestion. Well, his refusal sounded reasonable in a way. Running for 30 minutes is already difficult and boring enough. And I ask him to do it longer time! He asked me to find an evidence to prove that we have to do 40 minute cardio to lose fat.

I surfed the net, only to find out that everyone says different stories. Their doctors say that we would hurt ourselves if we do more than 40 minutes cardio. Some researches show that high intensity intervals(HII) works better for women while low intensity, long duration cardio(LILDC) works better for men. Some experts say that you can lose as much as body fat with short intensive cardio. There are some people that say ’start with 20 minutes but make it 30, 40 or even more if your goal is losing fat.’

After reading lots of articles or personal stories and knowledge, I made my conclusion.

In losing body fat, the focus is how many calories is expended during and after workout, not how long or how strong we should do cardio workouts. It’s believed that high intensity cardio make us burn more energy after workout and increase our metabolic rate. But it’s also said that longer cardio workout may work better as long as it’s intense enough, not too low, not necessarily high all the way through. Medium or medium-high intense cardio may work better for people who are relatively more overweight because high intensity exercise may cause them knee or other health problems.

So here is what I’ll do. I’m relatively fit with relatively strong endurance. I’ll try high intensity intervals three times and low intensity, long duration cardio twice per week.

My duration:

High intensity intervals(HII): 25 ~ 30 minutes

Low intensity, long duration cardio(LILDC): 35 ~ 40 minutes