Body positivity doesn’t forbid weight change, but it asks you to focus on behaviors (e.g., more vegetables, better sleep) rather than the number on the scale. Weight may or may not change — and your worth is unchanged either way.
The first step is decoupling exercise from punishment. If you are working out because you ate a piece of cake, you are in a toxic relationship with movement. Instead, ask yourself: What does my body need to feel good today?