Belly fat may be bad for your brain. A number of recent studies widely publicized in the media, have suggested that excess adipose tissue (body fat), particularly around the belly, during a persons’ midlife years may increase the risk of developing dementia, including Alzheimer disease (AD), during old age. AD is the most common type of dementia among older people.
Just how adipose tissue and its many chemical components may affect the brain is a complex story that researchers are eagerly investigating, with support from the National Institute of Aging (NIA). “We have two very serious public health burdens – Alzheimer disease and obesity- and if they interact so that one accentuates the other, then this is obviously a significant crisis”, says Dr. Suzana Petanceska, a program director in the NIA’s Division of Neuroscience. “This is very important to know because if metabolic abnormalities associated with obesity do indeed harm the brain, and we are able to understand how that happens, there is a great potential for intervention”.
“Several epidemiological studies already show an association between body mass index (BMI) and dementia”, says Dr. Lenore Launer, chief of NIA’s Neuroepidemiology Section of the Laboratory of Epidemiology, Demography, and Biometry. (BMI is a measurement of body fat relative to height and weight). In support of these findings, there are also “a lot of interesting new experimental data on proteins such as leptin that are involved in obesity and may indeed be involved in the physiology of brain changes,” Dr. Launer says.”It’s an exiting area that needs to be explored”.
The epidemiological evidence: At first, researchers did not consider obesity to be an independent risk factor for dementia – separate from the conditions obesity spawns, including diabetes and cardiovascular disease. Numerous studies have linked both diabetes and cardiovascular disease to dementia. In the early 2000s, researchers turned their attention to obesity itself as an independent threat to the brain.
With support from NIA, Dr. Deborah Gustafson, Associate Professor, Neuropsychiatric Epidemiology Unit, University of Gothenburg, Sweden, and her colleagues analyzed data on dementia incidence in 290 Swedish women who were age 70 at the beginning of the study. Women who developed dementia in their 80’s had an average BMI at the age 70 that was two units (kg/m2) higher that that of women in another population study in Gothenburg showed that those with atrophy in their brains’ temporal lobes where likely to have higher BMIs.
Since then, imaging studies have “convincingly demonstrated both generalized and regional brain atrophy and changes in white matter in association with obesity,”writes Dr. William Jagust, a neurologist at the University of California, Berkeley, in the special issue on obesity and dementia of Current Alzheimer Research (April 2007).
Effects of belly fat:
“The more we understand about adipose tissue, the clearer it becomes that belly fat is its own disease-generating organism,” says Dr. Launer.”Your fat is a very active endocrine organ that has a life of its own,” Dr. Petanceska explains. As part of that life, it interacts with many other systems in the body. “How it interacts with the brain may profoundly inform us about brain aging and Alzheimer,”she adds.
We normally associate the changes that belly fat initiates with aging, so some researchers suggest that fat may accelerate the aging, so some researchers suggest that fat may accelerate the aging process. For example, visceral fat increases a person’s risk of developing insulin resistance, to which older people are more prone than are young people. Insulin resistance is a condition in which the body cannot use insulin properly. This condition typically leads to high levels of insulin in the blood, yet low levels of insulin activity in the brain. NIA-funded studies, including work by Dr. Suzanne Craft, Veteran’s Administration (VA) Puget Sound Healthcare System and the University of Washington, Seattle, indicate a correlation between insulin resistance and the risk of age-related memory impairment and Alzheimer disease.
Belly fat churns out a host of hormones, including cortisol and glucocorticoids known as stress hormones, which normally increase with age as well as during stress and are believed to affect cognition. The hippocampus, one of the main areas of the brain affected in AD is rich in receptors for glucocorticoids. An elevated level of cortisol has been linked to hippocampal atrophy in humans” writes Dr. Jagust.
The brains of AD patients show many signs of chronic inflammation. In addition, elevated levels of pro-inflammatory cytokines in the blood have been associated with a greater degree of age-related cognitive decline. Many of the substances produced by adipose tissue, known as adipokine, serve as mediators of inflammation(cytokines). The white adipose tissue that makes belly fat secretes cytokines that fuel and maintain a state of chronic inflammation,which is harmful to the body and may be one of the ways by which belly fat can accelerate brain aging and cause brain dysfunction.