Adherence to long term caloric restriction requires pertinacious effort on the part of the practicer. Even though long term adherence can be difficult to maintain, imagine the benefits that are associated with it: increased longevity, better health and cognitive improvement. Now you may question the latter assertion of mine; that reducing caloric consumption can improve cognition. But it's true. Caloric restriction has been empirically shown to increase a neurotrophin called BDNF. BDNF, a secreted protein released in the brain during exercise, can also increase in the hippocampus (but decreased in the Hypothalamus) in response to fasting and caloric restriction. BDNF is a neurotrophin. Neurotrophins are nerve growth factors that aid in the process of neurogenesis (creation of new brain cells) and strengthen synaptic plasticity. Studies published by researchers validate the multiple neurobiological benefits that occur in response to intermittent fasting and caloric restriction. If you don't believe me, Google it.

Other studies show that the number of mitchondria, or the powerhouses of the cell, is increased to compensate for low ATP production. This is called mitochondrial biogenesis. Because caloric restriction provides less energy to cells, cells compensate by producing more mitochondria to maintain sufficient energy. This means the cell produces less oxidative stress because of better energy efficiency, while also mitigating future harm to the mitochondria. This also reduces the risk of several mitochondrial diseases that some scientists believe are caused by deleterious effects to mitochondrial DNA.

This additionally means that as you become adjusted to staying on a caloric restricted diet, your body's level of energy increases. Of course, when you first practice caloric restriction, you feel tired because your body hasn't responded quickly enough by producing more mitochondria. This is normal and the fatigue should stop after a couple weeks of continuing CR.

The other reason why CR reduces cognitive impairment is simply  due to better glucose tolerance. Excessive glucose in the blood causes inflammation by creating AGEs (advanced glycation end products). We all know that AGEs cause McDonald's fries to brown during frying. The reason why McDonald's fries turn brown is because McDonald's uses sugar during the cooking process. This oxidizes the fries. Just imagine the oxidation that occurs in the human body if you eat too much sugar. You're basically "browning" your brain.