16:8 Time-Restricted Feeding Extends Lifespan and Improves Gut Health in Drosophila

Dietary timing is emerging as a powerful modulator of metabolic health, independent of caloric intake. Time-restricted feeding (TRF)—limiting food consumption to a defined daily window—has shown promise in reducing insulin resistance, improving cardiovascular markers, and extending lifespan in several model organisms. However, whether a stricter 16:8 TRF protocol confers greater benefits than milder 12:12 regimens, and whether short early-life TRF exposure produces lasting effects, remained open questions.

This study used mated female Drosophila melanogaster (w1118 strain, aged 3–5 days) as a tractable model. The TRF protocol consisted of 8 hours of food access beginning at Zeitgeber time 0, followed by 16 hours with access only to water-agar (1–2% agar) to prevent desiccation—structured as 6 consecutive TRF days per week with one ad libitum recovery day. Control flies had continuous unrestricted food access. The researchers tested TRF applied lifelong, for 4 weeks, for 2 weeks, and for as little as 1 week in early adulthood, then measured survival, fecundity, starvation resistance, locomotor activity, body composition (triglycerides and protein), gut integrity (the 'smurf' assay using blue dye leakage), intestinal stem cell (ISC) proliferation, and gut microbiota composition via 16S rRNA sequencing.

Lifelong TRF significantly extended median and maximum lifespan compared to ad libitum controls (Mantel-Cox log-rank test, p<0.0001). Notably, even 2-week early-life TRF produced a statistically significant lifespan extension that persisted after returning to ad libitum feeding, demonstrating that transient early interventions can have durable longevity benefits. A 4-week TRF window showed a similar, robust effect. Starvation resistance was modestly enhanced after TRF, suggesting improved energy homeostasis.

Importantly, TRF did not reduce fecundity during the most reproductively active phase of adult life—a critical finding given the classic longevity/reproduction trade-off observed in many dietary restriction paradigms. Body fat (triglycerides) and protein levels were not significantly altered, and locomotor activity monitored over 72-hour periods showed no impairment, ruling out a generalized debilitating effect.

In aged flies, TRF dramatically reduced the frequency of 'smurf' phenotypes—flies whose blue-dyed gut contents leaked into the body cavity, indicating intestinal barrier failure. TRF also suppressed excess ISC proliferation, a well-established marker of gut aging and dysbiosis in Drosophila. Microbiome analysis revealed that TRF shifted community composition toward greater representation of gram-negative bacterial taxa, though the functional significance of this shift requires further investigation.

The authors propose that the mechanism underlying these benefits likely involves circadian-gated autophagy induction and metabolic reprogramming—pathways activated by fasting intervals that are more robustly stimulated by 16-hour versus 12-hour fasts. These findings position 16:8 TRF as a non-invasive, low-cost intervention capable of simultaneously promoting longevity, gut health, and microbiome balance without meaningful trade-offs in reproductive output or physical fitness.