Obesity is an important risk factor for many chronic physical and mental illnesses. The generally accepted view is that being overweight causes similar health problems to obesity, but to a lesser degree.
More than 85% of those with hypertension have a BMI greater than 25. The risk of hypertension is 5 times higher in the obese as compared to those of normal weight. A definitive link between obesity and hypertension has been found using animal and clinical studies, 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. The association between hypertension and obesity has been also well described in children.
One of the strongest links between obesity and disease is that with type 2 diabetes. These two conditions are so strongly linked that researchers in the 1970s started calling it "diabesity". Excess weight is behind 64% of cases of diabetes in men and 77% of cases in women.
Gynecomastia
Obesity, according to a 2009 review, can be associated with elevated peripheral conversion of androgens into estrogens in some individuals.
Due to its association with insulin resistance, the risk of polycystic ovarian syndrome increases with adiposity. 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 leads to infertility in both men and women. This is primarily due to excess estrogen interfering with normal ovulation in women and altering spermatogenesis in men. 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 men, 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 women have more than twice the rate of C-sections compared to women of normal weight. Obese women also have increased risk of preterm births and low birth weight infants.
Those who are obese have a rate of dementia 1.4 times greater than those of normal weight.
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.
Multiple sclerosis
Women that are obese at age 18 have a greater than twofold increased risk of MS.
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 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.
Obesity has been associated with depression. The relationship 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
A 2011 systematic review indicated that obese people draw negative reactions, furthermore people are less willing to help the affected individual in any situation.
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. It is believed that a systemic pro-inflammatory state induced by some causes of obesity may contribute to airway inflammation, leading to asthma.
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 show to worsen lung function in asthma and increase the risk of developing an asthma exacerbation.
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Gout
Compared to men with a BMI of 21–23, men with a BMI of 30–35 have 2.3 times more gout, and men with a BMI of greater than 35 have 3.0 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.
, stress, and mixed incontinence all occur at higher rates in the obese. The rates are about double that found in the normal weight population. Urinary incontinence improves with weight lost.
