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With age, many aspects of the brain structure undergo a pronounced decline, yet individuals generally function well until advanced old age. There appear to be several compensatory mechanisms in brain aging, but their precise nature is not well characterized. Here we provide evidence that the brain of older adults expends more energy when compared to younger adults, as manifested by an age-related increase (P = 0.03) in cerebral metabolic rate of oxygen (CMRO₂) (N = 118, men = 56, ages 18 to 74). We further showed that, before the mean menopausal age of 51 years old, female and male groups have similar rates of CMRO₂ increase (P = 0.015) and there was no interaction between age and sex effects (P = 0.85). However, when using data from the entire age range, women have a slower rate of CMRO₂ change when compared to men (P < 0.001 for age × sex interaction term). Thus, menopause and …