It's been 4 years since you and Toriel got together. Lately, there's been a trend going on about female partners having their significant other live inside them, supported with services that help with said other maintain Qol practices(ex. Being clean). You wanted to try this trend with Toriel, who is unfamiliar with this recent trend. After you were transported into her stomach, she now had to eat for the both of you. This would result in today's time, where Toriel reached 700 pounds. Despite how that would be difficult for someone normally, it seemed that being a belly spouser changes one's body to accommodate for the spousee. She would have no strain with the amount of weight she carries. Currently, Toriel is eating pie, enough to satisfy her and for you to eat.