肥満関連罹患率

Obesity-associated morbidity/ja
Obesity-associated morbidity/ja
	肥満は、人々の生活の質に悪影響を及ぼす多くの医学的合併症を引き起こす可能性がある。
Specialty	内分泌学（その他の専門分野）

肥満は、多くの慢性的な身体的・精神的疾患の危険因子である。

肥満ではないが過体重であることの健康への影響については議論があり、過体重（BMI25.0～29.9）に分類される人の死亡率は、理想体重（BMI18.5～24.9）の人よりも実際に低い可能性を示す研究もある。過体重の人の健康リスクは、医療の改善の結果、時間の経過とともに減少している可能性がある。肥満に関連した病状の中には、肥満による直接的な影響ではなく、肥満者に対する医療上の差別によるストレスの結果であるものもあり、肥満者が受ける医療が比較的貧弱であるために悪化しているものもある。

医療差別

肥満には社会的スティグマがあるため、肥満の人は正常なBMI 体重の範囲内の人よりも貧しい医療を受ける可能性があり、肥満と悪い健康転帰の関係を助長している可能性がある。実際の体重の状態に関係なく、体重に関連した差別を経験する人は、体重に関連した差別を経験しない人に比べて、同様に健康上の転帰が不良である。また、肥満の人は、たとえ医学的な問題によって体重が増えたとしても、肥満でない人に比べて医療を求める傾向が低い。コロンビア大学健康政策・管理学部のピーター・ミューニッヒ教授は、肥満に関連した病状は「脂肪率だけからではなく、肥満であることに関連した社会的スティグマによって引き起こされる心理的ストレスからも引き起こされる」可能性があると提唱している。

心臓学的リスク

心臓発作（心筋梗塞）

体重は、現在（2014年現在）のリスク評価ツールでは、心血管疾患の独立した予測危険因子とはみなされていない。肥満が増加しているにもかかわらず、心血管疾患による死亡率は減少しており、少なくとも1つの臨床試験は、試験中の減量介入によって心血管疾患が減少しなかったため、早期に中止された。

虚血性心疾患

腹部肥満は狭心症や心筋梗塞などの心血管系疾患と関連している。しかし、全体的な肥満（BMIで測定）は心筋梗塞の誤診につながる可能性があり、急性心筋梗塞後の死亡率を低下させる可能性がある。

2008年、ヨーロッパのガイドラインは、ヨーロッパの成人の虚血性心疾患の35％は肥満が原因であると結論づけた。

鬱血性心不全

肥満があると、男性では心不全の約11％、女性では約14％が発症する。

高血圧

高血圧患者の85％以上はBMIが25以上であるが、おそらく食事は体重よりも重要な因子である。肥満と高血圧の関連は、動物実験および臨床研究において見出されており、肥満誘発性高血圧には複数の潜在的メカニズムがあることが示唆されている。これらのメカニズムには、交感神経系の活性化やレニン-アンジオテンシン系の活性化が含まれる。2007年の時点では、小児の高血圧と肥満の間に関連があるかどうかは不明であったが、小児の過体重が増加しているにもかかわらず血圧が上昇しているという直接的な証拠はほとんどない。

コレステロール値の異常

肥満は血液中のLDLコレステロールレベルの上昇とHDLコレステロールレベルの低下と関連している。

Deep vein thrombosis and pulmonary embolism

Obesity increases one's risk of venous thromboembolism by approximately 2.3 fold.

Dermatological risks

Obesity is associated with the incidence of stretch marks, acanthosis nigricans, lymphedema, cellulitis, hirsutism, and intertrigo.

Endocrine risks

Gynecomastia in an obese male

Diabetes mellitus

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

Gynecomastia

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

Gastrointestinal risks

Gastroesophageal reflux disease

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, and people who are severely obese have the most GERD symptoms. However, most studies find that GERD symptoms are not improved by nonsurgical weight loss.

Cholelithiasis (gallstones)

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

Reproductive system (or genital system)

Polycystic ovarian syndrome (PCOS)

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.

Infertility

Obesity can lead to infertility in both males and females. This is primarily due to excess estrogen interfering with normal ovulation in females and altering spermatogenesis in males. It is believed to cause 6% of primary infertility. 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. Being morbidly obese increases the odds ratio to 2.0.

Complications of pregnancy

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

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

Birth defects

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.

Intrauterine fetal death

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

Buried penis

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

Neurological risks

MCA territory infarct (stroke)

Stroke

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

Meralgia paresthetica

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

Migraines

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

Carpal tunnel syndrome

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

Dementia

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

Idiopathic intracranial hypertension

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.

Multiple sclerosis

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. 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.

Cancer

Hepatocellular carcinoma 1

Many cancers occur at increased frequency in those who are overweight or obese. A study from the United Kingdom found that approximately 5% of cancer is due to excess weight. These cancers include:

A high body mass index (BMI) is associated with a higher risk of developing ten common cancers including 41% of uterine cancers and at least 10% of gallbladder, kidney, liver and colon cancers in the UK. For those undergoing surgery for cancer, obesity is also associated with an increased risk of major postoperative complications compared with those of "normal" weight.

Psychiatric risks

Risk of death from suicide decreases with increased body mass index in the United States.

Depression

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

The association between obesity and depression is strongest in those who are more severely obese, those who are younger, and in women. Suicide rate however decreases with increased BMI.

Social stigmatization

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

Respiratory system

Obstructive sleep apnea

Obesity is a risk factor for obstructive sleep apnea.

Obesity hypoventilation syndrome

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.

Chronic lung disease

Obesity is associated with a number of chronic lung diseases, including asthma and COPD.

Complications during general anaesthesia

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

Obesity and asthma

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

COVID-19

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. 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. 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.

Rheumatological and orthopedic risks

Gout

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.

Poor mobility

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

Osteoarthritis

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

Low back pain

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

Traumatic injury

In females, low BMI is a risk factor for osteoporotic fractures in general. In contrast, obesity is a protective factor for most osteoporotic fractures.

Urological and nephrological risks

Urinary system

Urinary incontinence

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

Chronic kidney disease

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

Hypogonadism

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.

Erectile dysfunction

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