Prostate Cancer. A 2001 study reported that obesity was associated with a modest increase in prostate cancer mortality, although not with the risk for prostate cancer itself. Some evidence suggests that it is a high-calorie intake rather than obesity or fat intake increases the risk for prostate cancer.
 | Click the icon to see an image of prostate cancer. |
Breast Cancer. Studies have reported mixed effects on the association between obesity and breast cancer. A number of studies have linked obesity to breast cancer in postmenopausal women, particularly in women who begin to gain weight after age 18. One study, in fact, suggested that being heavier as a child conferred a lower risk for breast cancer after menopause.
 | Click the icon to see an illustrated series detailing a breast cancer surgery (mastectomy). |
Gallbladder Cancer. Obese women are at higher risk for gallbladder cancer.
Gastrointestinal Cancers. A number of cancers in the gastrointestinal tract have been associated with obesity:
- Cancer of the esophagus may be due to a higher incidence of gastroesophageal reflux disorder (heartburn) in people who are overweight.
- Colon cancer has been linked to increased body mass in both men and women.
- Pancreatic cancer and obesity have been weakly linked, with one study reporting a lower risk in overweight people who are physically active.
 | Click the icon to see an illustrated series detailing a colon cancer surgery. |
Muscles and Bones
Obesity places stress on bones and muscles. Studies report that the incidence of osteoarthritis is significantly increased in people who are overweight. People who are obese are also at higher risk for carpal tunnel syndrome and other problems involving nerves in their wrists and hands. It should be noted that some weight may be protective against osteoporosis (loss of bone density).
Eyes and Mouth Disorders
Obesity increases the risk for the following mouth and eye disorders:
- Gum disease
- Cataracts
- Maculopathy, an eye disease related to aging
Reproductive and Hormonal Problems
Infertility. Abnormal amounts of body fat, either 10 -15% too high or too low, can contribute to infertility in women. Obesity is specially related to certain problems related to infertility, such as uterine fibroids or menstrual irregularities. In men, obesity can contribute to reduced testosterone levels.
Effect on Pregnancy. The dangerous effects of obesity on pregnancy are multifold. They include high blood pressure, gestational diabetes (diabetes, usually temporary, that occurs during pregnancy), urinary tract infections, blood clots, prolonged labor, a higher fetal mortality rate in late stages of pregnancy, and cesarean delivery. Infants of women who are obese are also at higher risk for neural tube birth defects, which affect the brain or spine. Folic acid supplements, ordinarily effective in preventing these conditions, may not be as protective in overweight women.
Effects on the Lungs
Obesity is thought to be a risk factor for adult-onset asthma, although there is some evidence that although obesity causes wheezing and shortness of breath, it does not appear to be strongly associated with the disease mechanisms in the lungs that cause true asthma.
Obesity also puts people at risk for hypoxia, in which oxygen is insufficient to meet the body's needs. Obese people need to work harder to breathe and tend to have inefficient respiratory muscles and diminished lung capacity. The Pickwickian syndrome, named for an overweight character in a Dickens novel, occurs in severe obesity when lack of oxygen produces profound and chronic sleepiness and, eventually, heart failure.
Effect on the Liver
Nonalcoholic Fatty Liver Disease. People with obesity, particularly if they also have diabetes type 2, are at higher risk for a condition called nonalcoholic fatty liver disease, also called nonalcoholic steatohepatitis (NASH). It may occur in about half of people with diabetes and 20 - 50% of obese people, depending on how severe the obesity is. It can also occur in overweight children. This condition causes liver damage that is similar to liver injury seen in alcoholism. In some cases, it can be very serious and require liver transplantation.
Gallstones. The incidence of gallstones is significantly higher in obese women and men. The risk for stone formation is also high if a person loses weight too quickly. In people on ultra-low calorie diets, gallstones may be prevented by taking ursodeoxycholic acid (Actigall).
 | Click the icon to see an image of gallstones. |
Sleep Disorders
People who are obese and nap tend to fall asleep faster and sleep longer during the day. At night, however, it takes them longer to fall asleep and they sleep less than people with normal weights. In an apparent vicious circle, studies have suggested that obesity not only interferes with sleep but that sleep problems may actually contribute to obesity.
Sleep Apnea. Obesity, particularly the apple shape, is strongly associated with sleep apnea, which occurs when the upper throat relaxes and collapses at intervals during sleep, thereby temporarily blocking the passage of air. Sleep apnea is increasingly being viewed as a potentially serious health problem, including heart disease and stroke. Some studies suggest that among overweight people, those who have sleep apneas have a greater heart risk than those without them. Obesity may contribute to sleep apnea simply by fatty cells infiltrating the throat tissue, which could narrow the airways. In one study, the more obese a person with sleep apnea was, the higher the pressure on the airway and therefore the greater the obstruction of the airway. (Obstructive sleep apnea may also cause obesity itself, however, as sleepy people tend to be sedentary.) Some studies are even indicating that treating sleep apnea may help people lose abdominal fat.
Narcolepsy. A small European study found a link between narcolepsy (a sleep disorder characterized by excessive daytime sleepiness with frequent daily sleep attacks) and high BMI.
Emotional and Social Problems
Depression. A number of studies have reported an association between depression and obesity, particularly in obese women. There may be a number of factors to explain the link. In some cases of atypical depression, people overeat and may gain weight. Overweight people may also become depressed because of social problems and a poor self-image. In these cases, depression is usually resolved when people lose weight. There is also some evidence, however, that obesity itself may impair levels of tryptophan--a precursor of serotonin, which is a brain chemical associated with mental well-being. In one study, even after people lost weight, tryptophan levels were lower than normal. In any case, there does not appear to be any association between depression and obesity in men.
Social Problems. One long-term study reported that overweight young women completed fewer years of school, were 20% less likely to be married, and had 10% higher rates of household poverty than their thinner peer. Obese young men were also less likely to be married their incomes were lower than their thinner peers. Nevertheless studies consistently show that overweight males (both boys and men) are not as severely emotionally affected as females of any age. Women and girls tend to blame themselves for being heavy while males tend to attribute being overweight to outside factors.
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