The "starvation mode" idea comes from the Minnesota Starvation Experiment.

Wherein the subjects were starved. And are you ready for the punchline?

For months.

There is such a thing as a starvation response. A slight drop in basal metabolic rate, an increase in cortisol and a bunch of other changes. Psychologically, subjects were obsessed with food.

But it takes time to kick in. Weeks. Months even.

One or two days is not going to do it.