Let me explain it to you in a popular way. First, 1000 calories = 1 kcal = 1 kcal. And1000kj = about 300 calories.

The treadmill shows kilocalories. People engaged in light manual labor will consume about 2500 kilocalories a day. Even sleeping for 8 hours will consume about 500 kilocalories.

So to sum up, you only need to control your daily calorie intake below 2000 kilocalories to lose weight.