The more energy that a person uses during the day, the more food they need to eat for fuel. As the body breaks fat down, acids called ketones begin to build up in the blood. The presence of ketones in the blood and urine indicates that a person has entered ketosis. When a person has reached ketosis, their body is burning stored fat instead of glucose. To promote long-lasting and sustainable weight loss, it’s important to stick with any healthy dietary and lifestyle changes — even if you hit a plateau.