Evidence from the scientific community shows intermittent fasting to be beneficial in numerous species, including our own. The materials here discuss what I would call time restricted feeding rather than intermittent fasting. Restricting the hours that one eats during the day, but still otherwise eating ad libitum every day, can arguably be thought of as a mild form of intermittent fasting that doesn't rise to the level of, say, alternate day fasting or a quarterly five day implementation of the fasting mimicking diet. Nonetheless, there are benefits. It remains to be robustly determined in humans as to whether the benefits resulting from these milder forms of intermittent fasting are largely derived from a reduction in overall calories consumed or from undergoing periods of low calorie intake. Both have been shown to produce benefits in mice and rats, independently of one another.
Intermittent fasting diets fall generally into two categories: daily time-restricted feeding, which narrows eating times to 6-8 hours per day, and so-called 5:2 intermittent fasting, in which people limit themselves to one moderate-sized meal two days each week. An array of animal and some human studies have shown that alternating between times of fasting and eating supports cellular health, probably by triggering an age-old adaptation to periods of food scarcity called metabolic switching. Such a switch occurs when cells use up their stores of rapidly accessible, sugar-based fuel, and begin converting fat into energy in a slower metabolic process.
Studies have shown that this switch improves blood sugar regulation, increases resistance to stress, and suppresses inflammation for various periods of time. Because most Americans eat three meals plus snacks each day, they do not experience the switch, or the suggested benefits. Studies in both animals and people found intermittent fasting also decreased blood pressure, blood lipid levels, and resting heart rates. Evidence is also mounting that intermittent fasting can modify risk factors associated with obesity and diabetes. Two studies of 100 overweight women showed that those on the 5:2 intermittent fasting diet lost the same amount of weight as women who restricted calories, but did better on measures of insulin sensitivity and reduced belly fat than those in the calorie-reduction group.
More recently, preliminary studies suggest that intermittent fasting could benefit brain health too. A clinical trial found that 220 healthy, nonobese adults who maintained a calorie restricted diet for two years showed signs of improved memory in a battery of cognitive tests. While far more research needs to be done to prove any effects of intermittent fasting on learning and memory, if that proof is found, the fasting - or a pharmaceutical equivalent that mimics it - may offer interventions that can stave off neurodegeneration and dementia.