Ketosis is the state into which the body enters when it needs to burn fat. When blood glucose is low and stored reserves of energy have been exhausted, the body will start to burn the stored fat.
ketones are the product of ketosis. They are produced by the liver from fatty acids and the body uses them for the energy it needs. If the levels of ketones are high enough they can be detected in the urine using keto sticks obtainable from pharmacies. In this state the body is producing more ketones than it can use and this is not ideal.
On the Atkins diet this state of ketosis is actively sought and keto sticks are used to ensure that there is a small quantity of ketones in the urine. Ketones are acidic and if they are present in high levels as can happen in diabetics then they cause damage to the liver and kidneys (ketoacidosis). Normally, for the rest of us, this is not a danger as long as we keep the ketosis to a minimum.
Having low glucose levels in the blood either from a low calorie or low carb diet is the state that triggers ketosis. This is liable to make one feel sluggish and tired.It seems, though, that if carbohydrate levels eaten are kept to an optimum (this can be achieved by eating about 60g carbohydrate per day according to Atkins) then we feel more alert but fat burning will still occur. At this level we will only be producing the ketones we need for energy.
As far as I can make out, the body must be in ketosis to burn fat, so on any diet, if weight loss occurs then ketosis is in action. On a low carb diet the body is forced to burn fat even though calorie intake is high. The body is ‘tricked’ into burning fat because it is the carbohydrate in our diet that is converted into glucose and it is low glucose levels that trigger ketosis.
If you eat too much fat on a low carb diet then whatever can’t be processed by the liver enters the blood stream. It will be converted into ketones and used for energy before the stored fat is used. This seems to imply that eating too much fat will slow down weight loss but that ketosis may prevent some or all of the fat in the blood from being deposited in the arteries.
This information was partly found here http://www.holisticonline.com/Remedies/weight/weight_ketones-and-ketosis.htm
I can’t be sure of the original research source of the data above.