This is the 1382nd most frequent Portuguese word.
peso
Weight.
Here, 'peso' is used to describe a person's body weight, specifically the amount lost through dietary changes.
Ela perdeu peso após começar a dieta.
She lost weight after starting the diet.
Here 'peso' metaphorically refers to the burden or significance of responsibility.
Eu sinto o peso da responsabilidade.
I feel the weight of responsibility.
In this instance, 'peso' denotes the physical weight of the package, a measurable quantity.