Firstly, the longer you cook, the more nutrient loss occurs. Secondly, overcooked food is hard to digest and metabolize. Thirdly, when we cook starchy food at high temperatures for longer periods, the naturally occurring sugar and amino acids react to form harmful carcinogens like acrylamides. Whereas, overcooking of meat causes sugar, amino acids and a substance called creatine to react, producing carcinogens called heterocyclic amines. Lastly, while grilling, fat from the meat can drip onto the burning coal, leading to the production of carcinogens called polycyclic aromatic hydrocarbons.