The involuntary part of your brain gets confused because it received an "I ate" signal from your mouth but not your stomach. It responds by panicking: lowered metabolism and increased appetite.
Both effects have been shown separately. For instance, mice on fixed calorie diets become lethargic and gain weight if artificial sweeteners are added to their water.
Both effects have been shown separately. For instance, mice on fixed calorie diets become lethargic and gain weight if artificial sweeteners are added to their water.