Being Overweight or Obese Linked to Faster Brain Aging, Study Suggests

By Steve Tokar Being overweight or obese was associated with lower levels of biochemical markers of brain health, particularly in brain tissue involved in thinking and perception, according to a study of 50 otherwise healthy middle-aged adults conducted by researchers at the San Francisco VA Medical Center. A number of studies have shown a statistical association between being overweight at midlife and having an increased risk of developing Alzheimer's disease decades later, but this study was the first to show that excess weight is associated with abnormal brain chemistry that is indicative of risk for age-related dementia, according to lead author Stefan Gazdzinski, PhD, a neuroimaging researcher at the Center for the Imaging of Neurodegenerative Diseases at SFVAMC. "These results suggest that brains of people who are overweight or obese age faster than the brains of people of normal weight, and thus these individuals are at an increased risk of developing dementia," says principal investigator Dieter Meyerhoff, Dr.rer.nat., a radiologist at SFVAMC and a professor of radiology at the University of California, San Francisco. The study appears in the online Early View section of Annals of Neurology. Among the study subjects, a body mass index of 25 to 30, which is indicative of being overweight, or over 30, which is indicative of obesity, was associated with several abnormal brain biochemical deficiencies. These included lower than normal concentrations of N-acetyl-aspartate (NAA), a marker of neuronal health, in white matter -- the tissue that carries signals between brain cells -- in the frontal, parietal, and temporal lobes of the brain, as well as in grey matter -- the tissue where thinking and perception takes place -- in the frontal lobe. Reduced NAA is a known risk factor for cognitive decline and dementia in the elderly. The researchers also found lower than normal levels of compounds containing choline, which is essential to cell membrane synthesis, in frontal lobe white matter. The changes were found through magnetic resonance technology, a non-invasive method for obtaining detailed pictures of brain structure and function. "The changes in frontal lobe white matter are especially important because this area is more vulnerable to the effects of aging than is white matter in other lobes," observes Meyerhoff. Gazdzinski says the results are significant because of the worldwide increase in excessive weight and obesity. He notes that more than 150 million Americans -- about half the population of the U.S. -- are now overweight or obese, and that there are about 1 billion overweight and 300 million obese individuals around the world. The authors caution that the study is suggestive rather than definitive because data such as cholesterol, blood glucose, blood insulin, blood pressure, and additional markers of body fat and body fat distribution were not available for analysis. Since these factors might affect brain health, the authors say, they could potentially affect the results, if known. They also note that unrecorded differences in nutrition, exercise, fitness, health, and genetic predisposition among subjects might have affected the results. Nonetheless, they say that if their observations are confirmed in prospective studies that control for such factors, the results could lead to new understanding of some of the neurobiological changes leading to dementia in old age. Coauthors of the study were John Kornak, PhD, of UCSF, and Michael Weiner, MD, of SFVAMC and UCSF. The research was supported by funds from the National Institutes of Health, some of which were administered by the Northern California Institute for Research and Education.