Obesity and Dementia


The relationship between obesity and dementia is controversial. In the elderly there is an association of being underweight and Alzheimer’s disease.[1] However, mid-life obesity has been independently associated with increased risk of developing vascular dementia and Alzheimer’s disease. In the past decade, several studies have shown that midlife obesity as measured by body mass index (BMI) increases the risk of dementia later.[2]


In a retrospective Swedish twin study, it was found that individuals with Alzheimer’s disease had more than 70% higher odds of having been overweight at mid-life.[3] we are not clear about how obesity influences dementia risk. It’s theorized that the total body fat tissue may influence brain structures and functions through complex genetic and lifestyle-related processes.


Several biological processes may explain the association between obesity and dementia. For example, higher BMI is associated with diabetes and vascular diseases, which both increase dementia risk. Mid-life obesity may also reflect a lifetime of exposure to an altered metabolic and inflammatory state. This altered state may be caused by an interaction of genetic factors and early life environment.


Regardless of the underlying cause, the risk of dementia can be reduced by preventing mid-life obesity through nutrition and exercise. The Mediterranean diet has been associated with lower risk of developing Alzheimer’s disease. It is high in vegetables legumes, fruits, unsaturated fatty acids, and low intake of dairy products, meat, and saturated fatty acids with moderate alcohol use. Adherence to the Mediterranean diet is associated with a small reduction in the risk of developing mild cognitive impairment (MCI).  It also seems to reduce the risk for MCI to progress to Alzheimer’s disease.[4]


It’s not clear how the Mediterranean diet improves cognition. The same diet also lowers vascular risk factors such as high cholesterol, hypertension, and coronary heart disease. This would indicate that the protection may be from the prevention of vascular insults to the brain like strokes.[5] In addition, studies have shown that the Mediterranean diet may improve carbohydrate metabolism. It causes significant reductions in plasma glucose, serum insulin and leading to less insulin resistance.[6]


The definition of obesity is a BMI of 30 or greater; a BMI of 25-29 is considered over-weight; and a BMI of 20-24 is normal. A healthy diet of any kind also will reduce hypertension.  Refer to Healthy Diets for more information.



[1] Qlzilbash N, Gregson J, Johnson, ME et.al., BMI and risk of dementia in two million people over two decades: A retrospective cohort study, the Lancet, 2015;3(6):431-436.

[2] Rosengren A, Skoog I, Gustafson D, Wilhelmsen L. Body mass index, other cardiovascular risk factors, and hospitalization for dementia. Arch Intern Med 2005;165:321-326.

[3] Xu WL, Atti AR, Gatz M, et.al., Midlife overweight and obesity increase late-life dementia risk. Neurology 2011; 76:1568-1574.

[4] Scarmeas N, Stern Y, Mayeus R, et.al., Mediterranean diet and mild cognitive impairment, Arch Neurol. 2009;66(2):216-225.

[5] Singh RB, Dubnov G, Niaz MA et.al. Effect of an Indo-Mediterranean diet on progression of coronary artery disease in high risk patients (Indo-Mediterranean Diet Heart Study): A randomized single-blind trial. Lancet 2002;360(9344):1455-1461.

[6] Esposito K, Margella R, Ciotola M, et al. Effect of a Mediterranean-style diet on endothelial dysfunction and markers of vascular inflammation in the metabolic syndrome: A randomized trial. JAMA, 2004;292(12):1440-1446.