Abstract: We evaluated the changes in estrous cycle of female rats fed either high carbohydrate or high protein diets for 42 days relatively to commercially available rodent pellets. Animals fed high carbohydrate diet showed a lengthened estrus cycle while those fed with a high protein diet could not continue a healthy estrous cycle. Animals received a protein rich diet showed a lengthened estrus cycle with an atypically extended diestrous stage until protein rich food is withdrawn and a balanced diet was introduced. However, animals fed with a carbohydrate rich diet showed a typical estrous cycle but slightly lengthier. Present findings have shown that nutrition depletion affect on estrous cycle in rats.