Interleukin-6 and tumor-necrosis factor, found in both the periphery (produced by fat cells) and the brain (produced by neurons, astrocytes and microglia), which normally contribute to neurogenesis, neuroinflammation and synaptic plasticity, seem to be linked to cognitive decline, neurodegeneration and brain atrophy in obese people (Wilson et al., 2002; Griffin, 2006), as well as increased risk of dementia and Alzheimer's disease (Gustafson et al., 2004; Whitmer et al., 2005). This evidence concerns the gene TNF and Alzheimer disease.