If you lost 2kg/4.4lb in 1 day, chances are it was water weight coupled with bowel movements for the day.
Keep track of your weight on a daily basis (if you're dieting) and you'll better be able to see how what you eat and what you do affects your weight, that way you won't be confused again.
Ultimately though, you should focus on long term weight loss, not just losing X amount of weight in just 1 day.
Just find a good weightloss plan/system and implement it.
