Because it is a precursor to chemicals such as adrenaline, norepinephrine, and dopamine, L-tyrosine may be a suitable supplement choice for individuals attempting to lose weight because it may assist accelerate metabolism. Studies have shown that L-tyrosine supplementation increases the rate at which glucose enters the bloodstream during oral glucose tolerance tests. This effect appears to be independent of changes in insulin secretion or action. L-tyrosine has been used for years as a diet supplement to promote weight loss by allowing people to eat more without feeling full. Clinical studies have shown that it may help reduce food cravings and aid in fat loss when taken with or after a meal. However, not all foods containing tyrosine are created equal. Tyrosine levels vary between protein sources and can also differ based on how the protein is processed. High-quality proteins contain relatively high levels of tyrosine while low-quality proteins contain little to no tyrosine. People who choose to take L-tyrosine as a supplement should do so only under the supervision of a physician. Those seeking to lose weight should discuss with their doctor possible interactions with other medications or supplements they may be taking. Also, keep in mind that although L-tyrosine is safe when taken alone, excessive amounts of it may cause lightheadedness, dizziness, headache, nausea, diarrhea, and fatigue.