Menstrual cycle shortest and longest cycle lengths is considered very irregular. The average menstrual cycle lasts 28 days. The variability of menstrual cycle lengths is highest for women under 25 years of age and is lowest, that is, most regular, for ages 25 to 39. Subsequently, the variability increases slightly for women aged 40 to 44. The luteal phase of the menstrual cycle is about the same length in most individuals (mean 14.13 days, standard deviation 1.41 days) whereas the follicular phase tends to show much more variability (log-normally distributed with 95% of individuals having follicular phases between 10.3 and 16.3 days).
Menstrual cycle of food types has been found between PMS sufferers and non-sufferers. The different levels of ovarian hormones at different stages of the cycle have been used to explain eating behaviour changes. Progesterone has been shown to promote fat storage, causing a higher intake of fatty foods during the luteal phase when progesterone levels are higher. Additionally, with a high estrogen level dopamine is ineffective in converting to noradrenaline, a hormone which promotes eating, therefore decreasing appetite. In humans, the level of these ovarian hormones during the menstrual cycle have been found to influence binge eating. It is theorized that the