It took me 5 years to lose 10 kilos. The first 5 kilos took about a year with up to 8 hours a week at the gym and giving up nearly all fats, dairy etc. and eating what I thought was a healthy (high carb) diet. I could absolutely not shift anymore weight no matter how much exercise I did.
The second 5 kilos took me 5 weeks.....the first 5 weeks on Atkins induction and I was too tired to do any exercise at all!
Now my weight's steady with 30 mins walk every day and the low carb diet.