This open access paper provides a good high-level overview of what is known of the molecular mechanisms underpinning the beneficial response to calorie restriction and intermittent fasting.
Fasting works positively even when the total number of calories is not reduced. Image credit: Max Pixel, CC0 Public Domain
In short-lived species, quite sizable gains in life span are possible, though this is not the case for longer-lived species such as our own. The metabolic responses to calorie restriction and intermittent fasting are not the same; they appear to function through an overlapping set of mechanisms, such that intermittent fasting without reduction in overall calories can still improve health and extend life.
Citation:
Delayed functional aging in one parameter is not always necessarily linked to the extension of healthspan in different health parameters. In fact, by depending on the types of health parameters and experimental approaches, different healthspan results were observed from the studies that used the same long-lived mutant animals. Unlike healthspan, lifespan is unequivocally recorded by simply following the mortality of individual organisms. Lifespan extension in animal models is strongly correlated with a decrease in morbidity and an increase in health. Therefore, although we believe that results of health-related parameters from animal CR/IF studies are likely to be translatable to human healthspan, we will focus on the mechanisms of lifespan extension.
Link: https://doi.org/10.3390/nu12041194
Source: Fight Aging!