Especially when you are just getting started, because you lose like 2kgs in a a week and then plateau, and nothing works unless you really try optimizing your diet and activity and start accurately tracking calories and judging how much you eat, which takes practice, probably not an issue if you are extremely overweight but for someone like me who was at the BMI of 26 with very low muscle, you really need to optimize, especially as you start slimming down, it took me 8months to lose 16kgs, now I am pretty sure I could do it in 3 months