Among humans, increased interest in food intake normally occurs _____.

only after the production of glucose in the liver can no longer meet metabolic needs
when fewer calories are taken in than are expended, but only after the body depletes its reserves of fat in the liver
via chemical signals related to the amount of glucose stored in the liver and muscle cells
via chemical signals related to the amount of protein stores in the liver
via chemical signals released when the stomach is empty

via chemical signals released when the stomach is empty

via chemical signals released when the stomach is empty

Increased interest in food intake among humans normally occurs via chemical signals released when the stomach is empty.

Among humans, increased interest in food intake normally occurs via chemical signals released when the stomach is empty.

To get this answer, we can analyze each option:

1. Only after the production of glucose in the liver can no longer meet metabolic needs: This option is incorrect because the question is asking about increased interest in food intake, not the production of glucose in the liver.

2. When fewer calories are taken in than are expended, but only after the body depletes its reserves of fat in the liver: This option is also incorrect because it mentions the depletion of fat reserves, which is not directly related to the increased interest in food intake.

3. Via chemical signals related to the amount of glucose stored in the liver and muscle cells: This option is incorrect because it focuses on the glucose stored in the liver and muscle cells, but does not address the empty stomach as mentioned in the question.

4. Via chemical signals related to the amount of protein stores in the liver: This option is also incorrect because it mentions protein stores, which are not directly related to the increased interest in food intake.

5. Via chemical signals released when the stomach is empty: This option is correct because it states that increased interest in food intake occurs when the stomach is empty, which aligns with our common understanding of hunger cues.

Therefore, the correct answer is: "Via chemical signals released when the stomach is empty."