Strength training can have a positive role in fat loss. If one goes on a diet with significant caloric restriction the body's response of self preservation is accomplished by lowering it basal metabolic rate. The body does this by catabolizing lean body mass. The weight loss will be both fat and muscle. If one strength trains the body receives the message that lean body tissue is vital to survive the demands placed on it. Rather than losing lean body mass the body preserves it and adds to it.
From Men's Health magazine article 5 Reasons You're Not Losing Weight: