I suppose the concern goes something like this. Under certain metabolic conditions, each fat cell (in a region) decides it needs to be size X, and grows / shrinks accordingly. And under other conditions, each fat cell (in the same region) decides it needs to be size X*3.
If there are more fat cells, then and they all decide to increase in size, then that could be a substantial weight gain, beyond what would be expected otherwise.
This is also common in all weight loss interventions, though the reason is generally from metabolic slowdown, not the creation of new adipose tissues.