DailyPractice

14 day challenge · Fasting

Fast Together

Two weeks of a 16 hour overnight fast with an 8 hour eating window, done alongside friends. Water, black coffee, and tea are fine. Skip it if you're pregnant, diabetic, or have had an eating disorder, and check with a doctor first.

The calendar

Every day: 16 hour fast, 8 hour eating window

What's changing in you

At 24 hours

since you started your fast, on average

Cells
20m1d3d

Just happened

Cell cleanup may pick up

Cells have a recycling system that breaks down worn out parts. Fasting turns it up in animals, and it may do the same in people.

Between 18 hours and 3 days, for many people

Next up

In 24 hours

Ketones climb and feed your brain

After 2 days without food, ketones are about 20 times higher than a few hours after a meal. Your brain starts using them for part of its fuel.

The first 2 days, hour by hour

Each line is an average shape, compared with the level named under it.

You
Start12h24h36h48h

  • Insulin in your blood

    27%

    Insulin, compared with its level about 4 hours after your last meal. It falls by about three quarters over the first day. This is an average shape from one small study, and people vary.

  • Ketones in your blood

    23%

    Ketones, compared with their level after 2 days without food. They barely move by hour 16, then climb steeply on day 2. This is an average shape from two small studies, and people vary.

  • Blood sugar

    99%

    Blood sugar, compared with its level about 4 hours after your last meal. Your liver holds it almost steady for a day, and it dips only about 15% by day 2. This is an average from one small study, and people vary.

Every change, step by step

By about 4 hours

Reached

Your liver takes over

A few hours after you eat, insulin starts to fall. Your liver now keeps your blood sugar steady by letting out sugar it stored earlier.

Well established

Between 12 and 36 hours

Reached

The switch to burning fat

Your liver's sugar store runs low, so your body starts burning more of its stored fat for energy. Scientists call this the metabolic switch.

Good evidence

Between 16 and 24 hours

Reached

Ketones start to rise

Your liver begins turning fat into ketones, a backup fuel. By hour 16 there are only a few more than usual, and by a full day there are about 5 times as many.

Good evidence

Between 18 hours and 3 days

Reached

Cell cleanup may pick up

Cells have a recycling system that breaks down worn out parts. Fasting turns it up in animals, and it may do the same in people.

Early or approximate

Between 2 and 3 days

In 24 hours

Ketones climb and feed your brain

After 2 days without food, ketones are about 20 times higher than a few hours after a meal. Your brain starts using them for part of its fuel.

Well established

By about 3 days

In 2 days

A growth signal drops

After about 3 days without food, your body lowers IGF-1, a hormone that tells cells to grow. High levels are linked to faster aging and some cancers.

Good evidence

Share your progress

A snapshot for your friends, or just for you.

WHAT'S CHANGING IN ME24 hours intoyour fast.My cells may be doing somecleanup.4changes so farDailyPracticedailypractice.ai

Everyone's body is different. Talk to a doctor before fasting, especially if you have diabetes, are pregnant, have had an eating disorder, or take medicines that affect blood sugar or blood pressure.

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