Chocolate contains a saturated fat called stearic acid which is a long chain hydrocardon with 16 carbons, which is unbranched. This fatty acid is believed to lower cholesterol levels possibly by being converted in the liver to oleic acid, a benign monounsaturated fat and hence although chocolate has a high fat content, blood cholesterol levels do not raise.
The structure of cholesterol is shown above and a major part of animal plasma membranes, it is also a metabolic precursor of the steroid hormones.
Chocolate of cause contains a lot of other fats and sugars. Fatty acids have four important roles in the body.
The sugars present in chocolate are mainly in the form of glucose and fructose which are used in glycolysis to produce energy.
Too much sugar and it is converted into glycogen which is stored in the body. While too much fat can cause obesity.