Source: Martina. "Measuring Ketones." Web blog post. KetoDietApp.com. Compumaster Ltd., 30 Nov. 2013. Web. 14 Apr. 2016. <http://ketodietapp.com/Blog/post/2013/11/30/Ketosis-Measuring-Ketones>.
Most people believe that in order to lose as much fat as possible, they need to restrict their carbs intake as much as they can. Here is an explanation of the main effects of a low-carb, ketogenic diet.
Currently, it's not clear what the full effect of such carbs restriction is. Some diet authors, including Atkins himself, supported the idea that more ketones equals more weight loss. The reasoning they gave was that ketones are, in fact, calories which are made from the breakdown of fat in the liver. Is that really a valid reason?
Although some fat loss may appear as a result of a potential "metabolic advantage" (more ketones / calories excrete), the most important factor for fat loss is natural appetite control. While urinary ketone excretion means that body fat is being excreted causing fat loss, the effect is minimal: Based on recent studies, the number of calories lost in the urine as ketones is not significant (100 kcal at most).
Anecdotally, higher levels of ketones may actually slow down fat loss. Individuals who maintain lower ketone levels (trace ketones) appear to lose fat more efficiently. Why does that happen? One explanation may be that high levels of ketones in the bloodstream may slightly raise insulin and block the release of free fatty acids from fat cells.
Also, when becoming keto-adapted, some individuals tolerate relatively greater carbohydrate intakes without disrupting ketosis. It's up to you to find your optimal carbs intake. As I've explained above, more ketones won't help you burn significantly more calories - no studies show such effects. As long as you stay in nutritional ketosis (0.5 to 3.0 mM), moderate amounts of carbohydrates can be added to your diet.
If you want to know more about ketone levels and their effect on fat loss, have a look at this post: Do Ketones Matter?