Unless you are <10% BF, it is not so easy to deplete leptin. The starvation mode myth came from an actual starvation study, which involved people eating at 50% of their BMR for months at a time.
Not to mention, weight loss is not fat loss. Think about it this way - just taking 25g creatine for a few days can easily bloat you 3-5lb. Daily fluctuations can easily span that range too.
I'd also mention that people forget that your BMR also decreases as you lose weigh. Someone who is 6 feet and 275lb has a different BMR if they get down to 200lb. It's a common mistake to forget that your caloric deficit was based on your initial weight/BMR, and not your current one.