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It's well-known that carrying too much weight puts stress on the heart, joints and organs, but now we're learning that obesity may even be a detriment to cognitive abilities, as suggested by a number of studies. 

High-fat diet may cause changes in the brain

One study conducted at the University of Washington and published in the Journal of Clinical Investigation revealed that obesity may induce physical changes in the brain that make it difficult to control eating habits. In fact, the researchers theorize that these effects may begin long before obesity sets in, as changes in mice's brains were observed immediately after eating a high-fat meal.

"That was quite a shock," said Michael Schwartz, a professor and director of the Diabetes and Obesity Center of Excellence at the University of Washington, in an interview with National Public Radio. "This might reflect fundamental biological changes in how the brain works that help explain why it's so hard to keep weight off."

The study shows said that a high-fat meal affected the rodents' hypothalamus, a part of the brain that helps regulate hunger, inflicting inflammation in the brain region. While it's true that human brains may react differently than the mice's did, the researchers noted that observations of 34 brain scans in people revealed similar results.

UCLA finds lower brain mass in obese individuals

Earlier, a team of researchers from the University of California, Los Angeles (UCLA) discovered that obese, elderly individuals had 8 percent lower brain mass than did older folks of normal weight. Additionally, people who were simply overweight had 4 percent less brain volume than their slimmer counterparts.

"That's a big loss of tissue, and it depletes your cognitive reserves, putting you at much greater risk of Alzheimer's and other diseases that attack the brain," said UCLA professor of neurology Paul Thompson, PhD, quoted on the university's website.

Even kids may be affected

Parents sometimes view chubby cheeks or belly rolls on their children as being cute, but moms and dads should know that overweight kids are at an increased risk of sleep-disordered breathing and cognitive impairment, according to a study at the University of Chicago.

Authors of the study observed more than 350 children with a mean age of 8, performing neurocognitive tests and during sleep studies. They found that body weight, breathing ability while sleeping and cognition all appeared to influence one another.

"The intricate interdependencies between (body mass index), (sleep-disordered breathing) and cognition shown in our study are of particular importance in children, as their brains are still rapidly developing," said study author Karen Spruyt, PhD.

But there may be hope

People who find themselves with a little extra something around the middle, or even full-on obesity, may be pleased to know that research published in the Journal of the American College of Nutrition indicates that cognitive function may be restored with weight loss.

Authors of this study examined the brain health of 50 obese individuals, measuring their cognition before and after weight loss. On average, the participants lost between 2 percent and 10 percent of their body weight, and those who were successful had better brain function and improved grip strength when compared to control subjects.

Individuals who are concerned that their excess body weight may put them at risk of dementia or Alzheimer's disease may want to speak with their health care providers about safe and effective weight-loss programs. This may not only get the heart and knees back in shape, but the brain as well.