Weight fluctuations are 100% normal and not always in your control. Depending on your macro intake, workouts, stress, sleep, hormones, etc. water retention can cause some drastic swings in your bodyweight.
Not to mention, if youre gaining muscle and losing fat at the same time, the scale wont budge even if your pants are fitting looser. So instead of living and dying by the scale, measure your progress in other ways.
The best way to tell if your hard work is paying off is by getting a body fat analysis done. This will show you exactly how much fat youve lost and how well your workouts are supporting lean muscle mass helping you look more toned in the end.
Other ways to measure progress include paying attention to how you feel, how your clothes are fitting, how your workouts are going, and daily progress photos.
Original post:
10 Things You Need to Know When Starting a New Diet - Muscle & Fitness