For the very overweight this is very likely; running a substantial daily caloric deficit just by eating healthy and drinking water will cause large early losses

For the very overweight this is very likely; running a substantial daily caloric deficit just by eating healthy and drinking water will cause large early losses. This isn't sustainable, however, and really just kickstarts the process. As someone nears a breakpoint (different for everyone) they'll fall into the one pound per week rule.