Most people feel better energy, sleep, and mood within two to four weeks of consistent CrossFit. Strength and stamina gains show up around six to eight weeks, and visible body-composition changes typically take about three months. Results depend most on consistency, nutrition, and recovery, not talent.
This is a direct answer from the CrossFit BC coaching team. Short version first, then the detail and the local context for training in Vancouver. If you want the same answer applied to your own situation, a coach will walk through it with you in person.