Obesity-associated morbidity

Abdominal obesity is associated with cardiovascular diseases including angina and myocardial infarction.[13][14] However, overall obesity (as measured by BMI) may lead to false diagnoses of myocardial infarction and may decrease mortality after acute myocardial infarction.[14]

In 2008, European guidelines concluded that 35% of ischemic heart disease among adults in Europe is due to obesity.[15]

Having obesity is associated to about 11% of heart failure cases in males and 14% in females.[16]

More than 85% of those with hypertension have a BMI greater than 25, although diet is probably a more important factor than body weight.[16] Risk estimates indicate that at least two-thirds of people with hypertension can be directly attributed to obesity.[17] The association between obesity and hypertension has been found in animal and clinical studies,[18] which have suggested that there are multiple potential mechanisms for obesity-induced hypertension. These mechanisms include the activation of the sympathetic nervous system as well as the activation of the renin–angiotensin–aldosterone system.[19] As of 2007, it was unclear whether there is an association between hypertension and obesity in children, but there is little direct evidence that blood pressure has increased despite increases in pediatric overweight.[20]

Obesity is associated with increased levels of LDL cholesterol and lower levels of HDL cholesterol in the blood.[16][2]

Obesity increases one's risk of venous thromboembolism by approximately 2.3 fold.[21][22]

The link between obesity and type 2 diabetes is so strong that researchers in the 1970s started calling it "diabesity".[16] Excess weight is behind 64% of cases of diabetes in males and 77% of cases in females.[25]

In some individuals, obesity can be associated with elevated peripheral conversion of androgens into estrogens.[26]

Several studies have shown that the frequency and severity of GERD symptoms increase with BMI, such that people who are underweight have the fewest GERD symptoms,[27] and people who are severely obese have the most GERD symptoms.[27][28] However, most studies find that GERD symptoms are not improved by nonsurgical weight loss.[27][29]

Obesity causes the amount of cholesterol in bile to rise, in turn the formation of stone can occur [16][30]

Due to its association with insulin resistance, the risk of obesity increases with polycystic ovarian syndrome (PCOS). In the US approximately 60% of patients with PCOS have a BMI greater than 30. It remains uncertain whether PCOS contributes to obesity, or the reverse.[31][32]

Obesity can lead to infertility in both males and females. This is primarily due to excess estrogen interfering with normal ovulation in females[16] and altering spermatogenesis in males.[33] It is believed to cause 6% of primary infertility.[16][34] A review in 2013 came to the result that obesity increases the risk of oligospermia and azoospermia in males, with an of odds ratio 1.3.[35] Being morbidly obese increases the odds ratio to 2.0.[35]

Obesity is related to many complications in pregnancy including: haemorrhage, infection, increased hospital stays for the mother, and increased NICU requirements for the infant.[36] Obese females also have increased risk of preterm births and low birth weight infants.[37]

Obese females have more than twice the rate of C-sections compared to females of "normal" weight.[38] Some have suggested that this may be due in part to the social stigma of obesity.[39]

Those who are obese during pregnancy have a greater risk of have a child with a number of congenital malformations including: neural tube defects such as anencephaly and spina bifida, cardiovascular anomalies, including septal anomalies, cleft lip and palate, anorectal malformation, limb reduction anomalies, and hydrocephaly.[40]

Maternal obesity is associated with an increased risk of intrauterine fetal death.[34]

Excess body fat in morbid obesity can, in some cases, completely obscure or "bury" the penis.[41]

Ischemic stroke is increased in both men and women who are obese.[16]

Meralgia paresthetica is a neuropathic pain or numbness of the thighs, sometimes associated with obesity.[42]

Migraine (and headaches in general) is comorbid with obesity.[43] The risk of migraine rises 50% by BMI of 30 kg/m² and 100% by BMI of 35 kg/m².[43] The causal connection remains unclear.[44]

The risk of carpal tunnel syndrome is estimated to rise 7.4% for each 1 kg/m² increase of body mass index.[45]

One review found that those who are obese do not have a significantly higher rate of dementia than those with "normal" weight.[46]

Idiopathic intracranial hypertension, or unexplained high pressure in the cranium, is a rare condition that can cause visual impairment, frequent severe headache, and tinnitus. It is most commonly seen in obese women, and the incidence of idiopathic intracranial hypertension is increasing along with increases in the number of people who are obese.[47][48]

Obese female individuals at 18 years of age have a greater than twofold increased risk of multiple sclerosis compared to females with a BMI between 18.5 and 20.9.[49] Female individuals who are underweight at age 18 have the lowest risk of multiple sclerosis. However, body weight as an adult was not associated with risk of multiple sclerosis.[49]

Obesity has been associated with depression, likely due to social factors rather than physical effects of obesity.[16] However, it is possible that obesity is caused by depression (due to reduced physical activity or, in some people, increases in appetite).[55] Obesity-related disabilities may also lead to depression in some people.[55] Repeated failed attempts at weight loss might also lead to depression.[55]

The association between obesity and depression is strongest in those who are more severely obese, those who are younger, and in women.[55] Suicide rate however decreases with increased BMI.[54] Similarly, weight loss through bariatric surgery is associated with increased risk of suicide.[56]

Obese people draw negative reactions from others, and people are less willing to help obese individuals in any situation due to social stigmatization.[57] People who are obese also experience fewer educational and career opportunities, on average earn a lesser income,[58] and generally receive poorer health care and treatment[5] than individuals who are "normal" weight.

Obesity is a risk factor for obstructive sleep apnea.[16][59]

CPAP machine commonly used in OHS

Obesity hypoventilation syndrome is defined as the combination of obesity, hypoxia during sleep, and hypercapnia during the day, resulting from hypoventilation.[60]

Obesity is associated with a number of chronic lung diseases, including asthma and COPD.[59] It is believed that a systemic pro-inflammatory state induced by some causes of obesity may contribute to airway inflammation, leading to asthma.[61]

Obesity significantly reduces and stiffens the functional lung volume, requiring specific strategies for respiratory management under general anesthesia.[62]

The low grade systemic inflammation of obesity has been show to worsen lung function in asthma and increase the risk of developing an asthma exacerbation.[63]

A study in England found a linear increase in severe COVID-19 resulting in hospitalisation and death for those whose BMI is above 23, and a linear increase in admission to an intensive care unit across the whole BMI spectrum. The difference in COVID-19 risk from having a high BMI was most pronounced in people aged under 40, or who were black.[64] A study from Mexico found that obesity alone was responsible for a 2.7 times increased risk of death from COVID-19, while comorbidities with diabetes, immunosuppression or high blood pressure increased the risk further.[65] A study from the United States found that there was an inverse correlation between age and BMI of COVID patients; the younger the age group, the higher its BMI.[66]

Compared to men with a BMI of 21–22.9, men with a BMI of 30–34.9 have 2.33 times more gout, and men with a BMI ≥ 35 have 2.97 times more gout. Weight loss decreases these risks.[67]

There is a strong association between obesity and musculoskeletal pain and disability.[68]

Increased rates of arthritis are seen in both weight-bearing and non-weight-bearing joints.[16] Weight loss and exercise act to reduce the risk of osteoarthritis.[69]

Obese individuals are twice to four times more likely to have lower back pain than their "normal" weight peers.[70]

Urge, stress, and mixed incontinence all occur at higher rates in obese people.[72] The rates of urinary incontinence are about double that found in the "normal" weight population.[73] Urinary incontinence improves with weight loss.[74]

Obesity increases one's risk of chronic kidney disease by three to four times.[75]

In males, obesity and metabolic syndrome both increase estrogen and adipokine production. This reduces gonadotropin-releasing hormone, in turn reducing both luteinizing hormone and follicle stimulating hormone. The result is reduction of the testis' production of testosterone and a further increase in adipokine levels. This then feeds back to cause further weight gain.[76]

Obese male individuals can experience erectile dysfunction, and weight loss can improve their sexual functioning.[77][78]