Every other lifestyle ingredient asks you to add something — heat, food, movement, sleep, people. Fasting is the one that works by subtracting. Give the body a real break from eating and it flips out of “store” mode and into “repair” mode. Where the daily formula supports the longevity switches, fasting throws them by hand — the two work on exactly the same machinery.
The metabolic switch
For the first several hours after a meal, you run on the sugar you just ate. Once the liver’s sugar stores run low — roughly 12 or more hours in — the body “flips a metabolic switch,” shifting to burning fat and producing ketones. This isn’t just a fuel change; ketones act as signaling molecules that quiet inflammation and turn on cellular-defense genes. In a landmark New England Journal of Medicine review, de Cabo and Mattson describe this repeated switching as the core of why intermittent fasting benefits health and aging.
Underneath, the fasted state lowers insulin and dials down mTOR (the “grow” signal), while switching on AMPK (the energy-sensor) and, crucially, autophagy — the cellular self-cleaning program that clears damaged proteins and worn-out parts. These are the same three levers caloric restriction pulls, and the same ones the formula is designed to support.
Why it does what a supplement can’t
A supplement can support autophagy and NAD⁺ metabolism; a fast triggers them directly. Recent work shows spermidine — the autophagy inducer in the evening formula — is actually required for fasting to switch autophagy on, which is a neat picture of the formula and the practice working as one.
And the effect reaches the pace of aging itself. In the CALERIE trial, the first randomized study of sustained caloric restriction in healthy humans, two years of modest restriction measurably slowed a DNA-based “speedometer” of biological aging. Fasting is one accessible way to borrow that same signal.
How to do it without making it a project
The best fasting protocol is the one you’ll actually keep. Most people get the majority of the benefit from the gentlest version:
Time-restricted eating
- Eat within a 10- or 12-hour window; work toward 8–10
- The easy move: stop eating after dinner, delay breakfast
- Earlier windows (finish by ~7pm) suit metabolism best
- Coffee, tea, and water are fine during the fast
Occasional longer fasts
- A once-in-a-while 24-hour fast, or a periodic lighter day
- Only once daily TRE feels effortless
- Not necessary for the core benefit
- Skip entirely if it feels stressful or triggering
Fasting and the formula, together
The overnight fast is already built into the rhythm of the system: RENEW closes the day and the fast runs through the night, when repair peaks. In the morning, taking RISE in the fasted window — before you break the fast — lets the NAD⁺ and sirtuin actives fire while insulin is still low and autophagy still active. The formula supports the switches; the empty stomach flips them; the spermidine in the formula helps the fast do its cleaning. One system, working from both sides.
The practice
Fasting is not for everyone
- Do not fast without medical guidance if you take insulin or a sulfonylurea, or other glucose-lowering medication — risk of hypoglycemia. Dose timing often needs adjustment.
- Avoid if you are pregnant or breastfeeding, underweight, or have a history of disordered eating.
- Older adults and anyone at risk of muscle loss should keep protein high on eating days and pair fasting with resistance training.
- If you take medication that must be taken with food, or have any chronic condition, check with your doctor first.
Selected research
- de Cabo R, Mattson MP. Effects of intermittent fasting on health, aging, and disease. N Engl J Med. 2019;381:2541–2551. PubMed 31881139
- Waziry R, et al. Effect of long-term caloric restriction on DNA-methylation measures of biological aging (CALERIE). Nature Aging. 2023. PubMed 37117782
- Spermidine is essential for fasting-mediated autophagy and longevity. Nat Cell Biol. 2024. Nature Cell Biology
- Sutton EF, et al. Early time-restricted feeding improves insulin sensitivity, blood pressure, and oxidative stress. Cell Metab. 2018. PubMed 29754952
Fasting is a lifestyle practice offered to support general wellbeing. It is not a treatment for any disease and is not appropriate for everyone; nothing here replaces the advice of your physician, particularly if you take medication or have a medical condition.