HOME / FASTING / 5:2

5:2 fasting

Five days of normal eating and two days of heavy restriction. It is a weekly pattern rather than a daily one, which is what makes it different from every other schedule here.

Worth knowing before you start: 5:2 is a calorie protocol, not a fasting window, so it works differently in Burn than a 16:8 does.

The week

Mon

Tue

Wed

Thu

Fri

Sat

Sun

Two restricted days, kept apart rather than back to back. Tuesday and Friday, or any pair that suits your week.

How it differs

A calorie target, not a clock

Every other schedule on this site is defined by hours. 5:2 is defined by what you eat on two days, which changes how you run it and how Burn fits around it.

THE RESTRICTED DAYS

A much smaller intake, spread or in one meal

Some people take it as one evening meal, which turns the day into a long fast with food at the end. Others split it across two small meals.

THE NORMAL DAYS

Normal means normal

Five days of ordinary eating, not five days of compensating for the other two. Treating the normal days as a reward is what makes this pattern fail.

IN BURN

Run it as a timed fast

Burn times fasting windows and names stages. On a 5:2 day, start a fast when you stop eating and let it run to your one meal. The stages then read like any other long fast.

One meal at the end

Taken as an evening meal, a restricted day is a long fast

Finish dinner on Monday, eat once on Tuesday evening, and you have run something close to a 22 hour fast. Burn tracks it the same way it tracks any other, through Fat Mobilisation and into Ketosis Entry.

Keep the two days apart

Back to back restricted days are much harder and give the week no recovery. Tuesday and Friday is the usual pairing.

Do not put them next to hard training

Plan the restricted days around your lighter sessions. Heavy training on very little food is a poor combination.

Salt and water through the day

A restricted day means very little sodium coming in with food, and most of the headaches on these days are electrolytes rather than hunger.

Electrolytes guide → Managing hunger →

Burn's timer at 20 hours 9 minutes, the stage pill reading KETOSIS

Burn's Insights screen showing Body Score, Hours per Week, Completion Rate and Avg Fast Length charts

5:2 suits you if

You would rather have two demanding days than a constraint every day

Your week has predictable quiet days you can choose

Daily windows keep colliding with breakfast meetings or family meals

You are comfortable tracking what you eat on two days a week

A daily window suits you better if

You prefer a routine that is the same every day

Counting calories is something you want to avoid

You train hard on most days of the week

Two very low days would be likely to trigger a large rebound

Start with 16:8 instead →

Where the evidence stands

Intermittent energy restriction has been studied in controlled trials and produces weight loss comparable to continuous restriction at matched intake. Those claims are drawn from peer-reviewed research and traced in our evidence packet. Burn does not publish calorie targets, and it does not set them for you.

Who should get advice first

Speak to a doctor before starting if you are pregnant or breastfeeding, have a history of eating disorders, manage diabetes, take medication timed to meals, or are under 18. Stop and eat if you feel unwell, whatever the plan says.

Time the long days properly

Run each restricted day as a timed fast in Burn, and see the stages, the history and the streak build week by week.

Download free on the App Store

iPhone, iPad, and Apple Watch. Requires iOS 18 or watchOS 11.