What do animals require in their diet? We can break down the answer into three main categories: essential nutrients, fuel, and raw materials. Animals can’t make essential nutrients on their own, so they must get these from food. A good balance of essential nutrients includes minerals, vitamins, and 8 amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. We also need fuel to keep our body going. We can use carbohydrates, proteins, and lipids (fats) to make ATP, our bodies’ energy currency. Carbohydrates are stored in the liver and muscles as glycogen. Our body can break down the glycogen into glucose when our body requires energy. Raw materials are required for biosynthesis. Since most of the molecules in our bodies are organic, we need enough carbon skeletons for repair, growth, and reproduction.

Now, how does our body regulate how much food we should eat? The answer is with a hormone called leptin. Leptin is produced by the adipose (fat) cells in our bodies. The more fat we have, the more leptin we produce. This hormone travels through the bloodstream and then binds onto receptors in the brain, specifically the hypothalamus. The result is that our appetite decreases and our metabolism increases.