Evidence that overnight fasting could extend healthy lifespan
A recent study by Ulgherait et al. has found that intermittent time-restricted feeding (iTRF) can extend healthy lifespan in fruit flies by promoting night-time autophagy, a process in which material in cells is degraded and recycled.
This finding suggests that timing could be a crucial factor in promoting longevity and health. While caloric restriction has been shown to extend lifespan in many species, it is difficult to implement for long periods of time due to the intense hunger it can induce.
In contrast, timing-based interventions like iTRF might be more sustainable. This article delves into the details of the study and the potential implications for promoting healthy lifespan in humans.
Evidence that overnight fasting could extend healthy lifespan
This post is a summary of the article “Evidence that overnight fasting could extend healthy lifespan” that was published online on 29 September 2021 by Stephen L. Helfand & Rafael de Cabo in the scientific journal “Nature”. To read the original article, click here.
In their study, Ulgherait et al. found that intermittent time-restricted feeding (iTRF) could extend healthy lifespan in fruit flies by promoting night-time autophagy, a process in which material in cells is degraded and recycled.
This finding suggests that timing could be a key factor in promoting longevity and health. While caloric restriction has been shown to extend lifespan in many species, it is difficult to implement for long periods of time because of the intense hunger it can induce. [1]
In contrast, timing-based interventions like iTRF might be more sustainable. Studies of intermittent fasting, which includes various types of TRF schedules that cycle between periods of fasting and eating, have consistently reported improvements in many health indices, even without reductions in calorie intake.
The benefits of intermittent fasting in humans include abdominal fat loss and improvements in glucose metabolism, blood pressure, heart-rate variability, and physical endurance. [2]
Moreover, many of the positive effects of caloric restriction on metabolism, organ function, and disease resistance seen in humans can be recapitulated with intermittent fasting and can be dissociated from those of weight loss and total caloric intake.
TRF and other types of intermittent fasting are lifestyle interventions that can be applicable worldwide and thus benefit people in a truly egalitarian way.
However, it is important to understand how TRF schedules promote health and extend lifespan.
Intermittent fasting induces a change from metabolism of sugar and carbohydrates to metabolism of fatty acids and other nutrients—a process called metabolic shifting.
The health contributions of this process must be distinguished from those of caloric restriction and weight loss to fully understand the responses to each of these dietary manipulations.
Ulgherait and colleagues modified a standard TRF schedule to include prolonged overnight fasting periods and found that this iTRF schedule increased lifespan by 18% in females and 13% in males compared with flies that had unrestricted access to food.
Moreover, iTRF not only improved lifespan but also protected against declines in muscular, neuronal, and intestinal function with age.
The optimal lifespan extension was achieved when iTRF was initiated at day 10 of the flies’ adulthood and terminated at day 40.
Beyond day 40, the authors observed no clear lifespan benefit with iTRF and a possible shortening of the remaining lifespan with TRF.
The authors ruled out the possibility that iTRF was inadvertently inducing a restriction in food intake, and indeed, flies on the iTRF regime ate more food than those with continuous access to food.
Furthermore, the combination of iTRF with caloric or dietary-protein restriction led to a greater lifespan extension than did either intervention alone, indicating that these manipulations extend lifespan through distinct mechanisms.
Altering signaling by the hormone insulin extends lifespan in many organisms, including fruit flies.
Ulgherait et al. found that flies with a lifespan-increasing alteration in insulin signaling lived even longer when the alteration was combined with iTRF, demonstrating that distinct mechanisms underlie the two interventions.
Feeding behavior and metabolism in flies, rodents, and humans are regulated by an internal 24-hour (circadian) clock, in which a set of genes interact to coordinate various cell functions according to the time of day.
In a series of experiments in mutant flies in which different clock genes were disabled, the authors demonstrated that the circadian clock is required for the health and lifespan benefits of iTRF to take effect.
This finding underscores the importance of timing in promoting longevity and health and suggests that the circadian clock might be a key target for interventions aimed at extending healthy lifespan.
Overall, the study by Ulgherait et al. provides valuable insights into the potential benefits and mechanisms of iTRF and highlights the need for further research to translate these findings to humans.
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