You probably know of tryptophan as an essential amino acid that is infamously found in turkey. According to your uncle, it’s the reason why he falls asleep after Thanksgiving dinner every year (that and the two bottles of wine he drinks). In fact, tryptophan is known to improve sleep and boost mood through its ability to elevate serotonin levels in the brain. A recent study seems to shows that it also helps you build muscle and lose fat. Animal research published in the journal Amino Acids described how rats who were given extra tryptophan enjoyed reduced fat deposition and increased oxidation of fatty acids. The scientists also found evidence of increased protein synthesis in the tryptophan group as well as reduced catabolism of dietary amino acids.