The three most important nutrient-sensing pathways in humans are insulin, mTOR, and AMPK. Each nutrient-sensing pathway provides different yet complementary information (see Figure 17.2). Insulin increases primarily in response to dietary carbohydrates and protein, and responds within minutes. mTOR increases primarily in response to dietary protein and plays out over eighteen to thirty hours. AMPK responds to overall cellular energy, which reflects the intake of all macronutrients. Its total effect runs over the longer term, from days to weeks.
