Yes, but the process and consequences depend entirely on when you decide to leave. There are two critical legal points in the MEPS process: enlistment in the Delayed Entry Program (DEP) and shipment to Basic Training.

Key Points of Separation:

Before Swearing into the Delayed Entry Program (DEP): You can walk away at any time without legal penalty. You are a civilian until you take the Oath of Enlistment.
After Swearing into the DEP, But Before Shipping: You are legally in the Inactive Ready Reserve (IRR). Leaving is possible but more complex. You must request a discharge from your recruiter and their command, which is not guaranteed. It may be considered an “Entry Level Separation” and is typically characterized as “Uncharacterized” or “Entry-Level Status” on your discharge paperwork.
After Shipping to Basic Training: Once you arrive at basic training, you have entered active duty. Leaving is extremely difficult and requires an administrative or medical separation process, not simply a request to quit.

Important Considerations:

While leaving the DEP carries minimal legal consequence, it is a serious commitment to break. You should inform your recruiter immediately.
Recruiters may try to convince you to stay, but they cannot legally force you to ship.

For related information on the physical standards you must meet to reach this point, you can read about What are the weight requirements for MEPS?.

For an external, detailed resource on Delayed Entry Program policies, you can review information from the Military.com DEP Guide.