Other complications and comorbidities associated with obesity are
a) Polycystic Ovarian Syndrome. The worldwide increase in the prevalence of obesity has led to an increase in comorbidities such as polycystic ovary syndrome (PCOS). In a genetic susceptibility setting, PCOS often manifests after weight gain, commonly in adolescence. PCOS is a common endocrinopathy that affects between 6 and 10% of women of childbearing age and presents characteristics such as hyperandrogenism, metabolic and reproductive dysfunction, as well as IR, independent of obesity, although it is amplified when it is present [
81]. Although the mechanism of IR in PCOS is not fully elucidated, the reported defects would be within the insulin receptor signaling pathway and low-grade inflammation that occurs in PCOS [
82,
83].
b) Obstructive Sleep Apnea. Obstructive sleep apnea (OSA) occurs in high prevalence in patients with obesity and coincides with several comorbidities such as hypertension, type 2 diabetes, dyslipidemia, non-alcoholic fatty liver disease, heart failure, and atrial fibrillation [
84]. It has been estimated that 58% of moderate to severe OSA is due to obesity [
85], and OSA is an independent riek factor for stroke (Jehan S, Farag M, Zizi F, Pandi-Perumal SR, Chung A, Truong A, Jean-Louis G, Tello D, McFarlane SI. Obstructive sleep apnea and stroke. Sleep Med Disord. 2018;2(5):120-125. Epub 2018 Nov 30. PMID: 30680373; PMCID: PMC6340906.). However, one should be aware of other risk factors, such as advanced age, male gender, peri- or postmenopausal states in the female gender, and craniofacial abnormalities [
86].
c) Cancer. Obesity is strongly related to increased susceptibility to various diseases, including different types of cancers, such as thyroid, uterine, liver, pancreatic, colorectal, breast, esophageal, and kidney cancers [
10,
26]. It is estimated that one in five cancers is related to obesity [
87]. Several mechanisms linking cancer to obesity have been proposed, such as IR, high levels of IGF-1, chronic low-grade inflammation in obese patients, deregulation of factors/hormones secreted by adipose tissue, and alterations in sex hormones [
88], as well as changes in the population of immune cells [
10]. See
Figure 4.