 In the ABCs of health consequences of obesity, if A is for arthritis, and B is for back pain and blood pressure, C is for cancer, and D is for diabetes, then E is for encephalopathy. Encephalopathy means brain disease. There's consistent data linking obesity and middle age to higher risk of dementia later in life. Overweight individuals have about a third high risk, and those who are obese in midlife seem to have about 90% greater risk of becoming demented. The risk isn't just limited to future dysfunction, though people with excess body weight don't appear to think as clearly at any age. Obese individuals show broad impairments in what are called executive functions of the brain, such as working memory and decision-making, planning, cognitive flexibility, and verbal fluency. These play a critical role in everyday life. People may think about their obesity and the resulting stigma they experience as much as five times an hour, but the cognitive deficits do not appear to rise just from distraction. There are structural brain differences between normal weight and overweight individuals. A review entitled Does the Brain Shrink as the Waste Expands noted gray matter atrophy across all ages among those carrying excess body fat. This reduced brain volume has then correlated with the lower executive function. A compromised integrity of the rest of the brain, the white matter, suggests accelerated brain aging, even in young adults and children with obesity. Cognitive deficits in young populations suggest it's something about the obesity itself that's affecting brain function rather than a later clinical consequence, such as high blood pressure. Purported mechanisms for this executive dysfunction include obesity-related inflammation and oxidative stress. So does weight loss improve cognitive function? Based on a meta-analysis of 20 studies, mental performance across a variety of domains can be significantly improved with even modest weight loss. Though no studies have yet been done to determine if this then translates into a normalization of Alzheimer's disease risk. F is for fertility, or rather failed fertility. Overweight couples struggling to have children should be educated on the detrimental effects of fatness. One meta-analysis concluded as weight loss is associated with an improvement in pregnancy rates among infertile women. Men also may suffer impaired fertility. The heavier a man is, the greater the risk of having a low sperm count or being completely sterile. This may in part be due to the effects of excess body fat on testosterone levels. Fat isn't just the primary site of estrogen production in post-metapausal women, but in men as well. There's an enzyme in body fat that actually converts testosterone into estrogen. Men even going from obese to just overweight could potentially raise testosterone levels in their blood 13%. A more dramatic cause of infertility in obese men is called hidden penis, also referred to in the medical literature as buried penis, concealed penis, or inconspicuous penis. It occurs when the excess fat in the pubic area subsumes the male member, since the base of the penis is attached internally to the pubic bone. It's also called trapped penis, because the moist and folding skin surfaces can result in a chronic inflammatory dermatitis leading to scarring, requiring a surgical intervention. So F may also stand for free willy.