Final answer:
Anna's low carbohydrate diet promoted a reduction in body fat by causing her body to enter a state of ketosis, where it switched to using fat as its primary source of energy.
Step-by-step explanation:
The body's metabolism shifts to a state of ketosis when there is a reduced intake of carbohydrates in the diet. Ketosis occurs when the body starts using fat as its primary source of energy instead of glucose. During ketosis, the liver produces ketone bodies, which are byproducts of fat metabolism. These ketone bodies are then used by the body as a source of energy, leading to a reduction in body fat.
In Anna's case, her low carbohydrate diet forced her body to switch to using fat as its energy source. As a result, her body started breaking down stored fat molecules and converting them into ketone bodies. The presence of ketones in her urine confirmed that her body was utilizing fat for energy. By sticking to the diet and promoting ketosis, Anna was able to reduce her body fat and lose weight.