The body is an intricate machine. If you do not keep it stoked, the metabolism will slow in a starvation perception response, thus slowing thyroid output, etc. This will grind your fat loss to a screeching halt. The body is programmed from early times to survive(mainatain fat stores in response to long fasts sand stress such as running through endless deserts, running from predators, etc.)...unfortunately it does not care about looking good at the beach.