Menopause is a period of significant physiological changes that may be associated with increased body weight and obesity-related diseases. Many researches were conducted to assess the contribution of factors such as estrogen depletion, REE decline, and aging to weight gain. An increase in orexin-A plasma levels, paralleling lower estrogen levels, was found during menopause. Orexins are hypothalamic neuropeptides recently discovered, involved in the regulation of feeding behaviour, sleep-wakefulness rhythm, and neuroendocrine homeostasis. Orexins might offer the missing link between postmenopausal hypoestrogenism and other manifestations of the menopausal syndrome, including appetite and weight changes and increase in cardiovascular risk. Menopause is a period of significant physiological change that is largely related to estrogen depletion and subsequent cessation of ovarian function. During menopause period, women tend to gain weight and FM (fat mass) [1]. It is not clear whether the increase in adiposity is a consequence of the decline in endogenous estrogen. Several studies faced the question by using postmenopausal hormone-replacement therapy (HRT). If the increase in adiposity is a consequence of the decline in endogenous estrogen that occurs at this time, HRT should prevent or reduce body fat gain. However, existing clinical data addressing this issue are discordant. Anderson et al. [2] showed that short-term (2 months) use of HRT did not alter body mass index (BMI), FM, or fat-free mass (FFM) in postmenopausal women [3]. With long-term use (1 year), Reubinoff et al. [4] found a similar increase in body weight and FM among women taking HRT and those who declined its use. They did, however, observe that there was a significant shift from gynoid to android fat distribution only in women not taking HRT [5]. A decrease in body weight was found by Espeland et al. [6] over a 3-year period in women taking HRT compared to women not taking HRT. Conversely, other data suggested that oral estrogen might cause an increase in body fat, possibly by limiting lipid oxidation [3, 7]. Thus, whether and how hormone therapy affects body composition in postmenopausal women is still unclear. Ovarian hormones may influence body composition through several potential mechanisms. It has been suggested that estradiol inhibits the action of adipose tissue lipoprotein lipase, the enzyme that hydrolyzes circulating triglycerides, allowing for the uptake of fatty acids into adipocytes [5]. Data from rodent models indicate that estrogen acts as an anorectic, decreasing voluntary
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