Many people give up on a fasting schedule too early because the scale jumped for a day, or keep going with one that isn’t helping because they never defined what “working” means. This page explains how to set a clear goal, which measurements are useful and which are mostly noise, how long changes usually take to show, and the signs that mean you should adjust your approach or stop.
Table of Contents
What Working Actually Means
Define this before you measure anything. “Working” depends on the goal:
- Weight loss: a downward trend in average weight or waist size
- Body composition: waist smaller, strength maintained or improving
- Health markers: blood pressure, blood sugar, or cholesterol results, as monitored with your healthcare provider
- Energy and routine: feeling steadier during the day, fewer unplanned snacks
- Sustainability: being able to keep the schedule for months without it taking over your life
Vague goals lead to vague evaluation. Pick one or two concrete goals. If you have a health condition such as diabetes or fatty liver disease, agree on goals and monitoring with your healthcare provider — fasting is not a substitute for treatment.
Useful Metrics
For weight management
- Weekly average weight (daily readings averaged over 7 days)
- Waist circumference at the navel, weekly, same time
- Photos monthly, same lighting and pose
- How your clothes fit
For body composition
- Strength in your main exercises
- Waist measurement
- A DEXA scan, if available, for a more detailed picture (repeat no more than every few months)
- Skinfold calipers or bioimpedance scales, used only for trends — single readings are not very accurate
For health markers
Which tests to have, and how often, is a decision for you and your healthcare provider. Common ones include:
- HbA1c and fasting glucose (blood sugar)
- Cholesterol and triglycerides
- Liver enzymes
- Blood pressure (a home monitor, averaged over several readings, is useful)
See bloodwork markers for what these tests measure.
For sustainability
- How many days you actually followed your schedule
- How easy it felt (a simple 1-10 rating each week)
- Sleep duration and quality
- Energy level (a 1-10 rating, averaged over the week)
Noisy Metrics to Be Cautious With
- Daily scale weight (day-to-day swings of 1-2 kg are normal)
- Daily energy or mood (high day-to-day variation)
- A single blood test result on its own
- Day-to-day changes in digestion
- A single workout (sleep and stress affect it a lot)
Use these as aggregate trends, not individual data points.
Metrics to Mostly Ignore
- Single-day water weight fluctuations
- Bloating measurements (high within-day variation)
- Subjective “I feel fat today” assessments
- Comparisons to other people’s progress
- Ketone readings (they vary widely and a higher number doesn’t mean more fat loss)
- Step count alone
- Hours fasted on their own (the schedule is a means, not the goal)
How Long to Give It
These are rough guides, not promises — everyone responds differently, and some people see little change.
- How you feel (energy, focus, sleep): give it 2-4 weeks. The first week or two of adjustment is not a fair picture.
- Weight: trends usually become clear over 4-6 weeks; larger changes take months.
- Body composition: usually several months.
- Blood tests: HbA1c reflects roughly the previous 2-3 months, so it is rarely worth rechecking sooner. Follow your healthcare provider’s schedule for any tests.
- Sustainability: only becomes clear over several months.
By Goal: What to Track
Weight loss as primary goal
Weekly weight average, waist measurement, and monthly photos. Note honestly how many days you stuck to the schedule. Review at around 4, 8, and 12 weeks.
If you have diabetes
Only fast with your healthcare provider’s agreement, especially if you take insulin or sulfonylureas, which can cause dangerous low blood sugar. Monitoring (blood sugar checks, HbA1c, medication doses) should follow the plan you agree with your care team. See fasting and diabetes.
If you have fatty liver disease
Blood tests and any scans should follow your healthcare provider’s plan. Gradual weight loss is the main factor linked to improvement, whatever eating pattern you use. See fasting and fatty liver.
General health
Routine check-ups as recommended for your age; blood pressure and weight at home if useful; a monthly note on energy and sleep.
Energy and focus
A simple 1-10 rating each week, plus sleep duration. Give it 4-6 weeks before judging.
Review Cadence
- Weekly: weight average, waist, sleep, energy, adherence
- Monthly: photos, strength progression, subjective comparison to last month
- Every few months: overall progress review and adjustments if needed; blood tests only as advised by your healthcare provider
- Yearly: routine health check-up and a fresh look at whether the approach still suits you
Signs It’s Not Working
- No change in weight or waist after about 8 weeks of consistent practice, if weight loss is your goal
- Blood test results getting worse
- Mood getting worse and staying worse
- Sleep getting worse
- Being unable to keep to the schedule most of the time
- Signs of eating too little (missed periods, hair loss, always feeling cold, dizziness)
- Increasing rigidity, food anxiety, or distress around eating
Some of these mean it is time to change your schedule; others — especially signs of under-eating, worsening mood, or anxiety around food — mean stop and talk to a healthcare provider. Fasting is optional: if it doesn’t suit you, regular balanced meals are a perfectly good way to eat. See fasting safety.
Frequently Asked Questions
I lost 3 kg in week 1. Is this real?
Most of it is likely water and stored carbohydrate (glycogen), not fat. Eating less at the start of any new diet often causes a quick early drop. After that, fat loss is much slower, and the pace depends mainly on your overall calorie intake.
Why has my weight stalled at week 4?
There are several common reasons, including eating more in the window over time, water retention, and normal fluctuations. See our plateau guide.
Can I tell from how I feel whether it’s working?
Partly. Better energy, sleep, and mood are useful signals, but they are also affected by everything else going on in your life. Combine how you feel with measurements.
Should I weigh daily or weekly?
Either works if you understand what you’re looking at. Daily with weekly averages is most informative. Weekly is fine if daily fluctuations stress you out.
How long should I give it before quitting?
If you feel well, around 6-8 weeks gives a fair picture. Stopping in week 2 won’t tell you much about whether the schedule suits you. But if you feel unwell or notice any warning signs, stop straight away — there is no need to push through.
What if I feel great but the scale isn’t moving?
It may be water retention hiding slow fat loss, or, if you are strength training, some change in body composition. Check your waist measurement and photos. It is also possible that you are not eating less overall; if weight loss is your goal, a week or two of tracking food can show this.
The Bottom Line
Decide what “working” means before you start. Use weekly averages rather than daily readings, combine how you feel with simple measurements, and give it a fair trial of several weeks. Leave medical tests and their timing to your healthcare provider. If it isn’t helping or is making you feel worse, adjust or stop — fasting is one option among many.