I have many patients that want to get pregnant and lose weight at the same time. This is generally a bad idea (at least how most people do it). It has been my clinical observation that people who were dieting (esp. through caloric restriction) did not get pregnant as easily. This study confirmed my clinical observations. They found that a hormone that produces hunger in the body (Ghrelin), suppresses LH in rats. Suppressing LH can translate into ovulatory problems, and we (the reproductive medicine community) currently believe if you aren’t ovulating, you won’t get pregnant. In this study they found that fasting (i.e., caloric restriction) made it even worse. Having said this, there are ways to lose weight and improve your fertility at the same time, but this has to be done carefully. One way is through metabolic typing.
 
Neurosci Lett. 2009 May 27