TRENDLINE FIT
Fat loss by daily maths. No diets, no forbidden foods, no goals to chase — an accounting system for your body. Enter your details and you get your daily calorie targets, a rules card for your phone, and a 28-day preview of your trend. Free, no signup — and nothing you type ever leaves this device.
Your Details
Pre-filled with an example — put in your own details and every number on this page rebuilds around you.
Your pace sets the deficit: your normal day sits exactly that far below maintenance, your quiet day goes a little deeper, and a splurge day is capped at maintenance — never above. A splurge pauses progress; it never reverses it.
⚠ At this pace your normal day drops below 1,200 kcal — lower than most adults should run. Pick a slower pace; the trend doesn't care how fast you go, only that you don't stop.
Your Daily Rules
WEIGH-IN
AM — 7-day average
LOG IT ALL
Every bite, every day
120 G PROTEIN
Daily ideal — floor 80 g
10,000 STEPS
Every single day
Targets, not tests — a day over or under isn't a verdict. The weekly average is what counts.
Your Calorie Scale
Every morning you pick a day type. The wall on the right is your maintenance — the most you ever eat. Everything left of it is progress at your chosen pace; the red zone is the only place damage happens, so the system simply never goes there.
The Volatility Simulator
This is your next 28 days at the pace you picked, starting from your weight. The grey line is what the scale will actually say each morning — noise, water, life. The gold line is your 7-day average. Watch what a salty weekend does — and doesn't do.
Your Rules Card
The card rebuilds itself live from your details — calories, protein, steps, maintenance. Save it to your phone. It's your whole system on one screen.
Articles
The sugar rollercoaster — spike, crash, cravings — is driving your snacking, not your character. Why sugar after dinner works, and the yum-per-calorie tip that makes it fit.
Read the article →Body Fat Calculator
The tape-measure method (the US Navy formula). Measure first thing in the morning, before food: waist at the navel, relaxed, not sucked in; neck just below the Adam's apple. Uses the height and sex you entered above.
An estimate, not a scan — the Navy method typically lands within a few points. What matters is what it does over months, measured the same way each time. Sound familiar? Trust the trend.
How These Numbers Work
No black box. Every number on this page comes from the formulas below — nothing else. Check them, replicate them, argue with them.
The honest limits: these are population averages, and your personal burn can sit 10–15% on either side of them — that's normal, not broken. Food labels are legally allowed to be off by up to 20%, so perfect inputs don't exist; consistent inputs do. And nothing here is a promise or medical advice — it's arithmetic: a starting estimate that your own trend then corrects. One boundary we won't soften: if your normal day lands under ~1,200 kcal, slow the pace — very low targets belong with professional guidance, not willpower.
Sources: Mifflin MD et al., “A new predictive equation for resting energy expenditure in healthy individuals,” American Journal of Clinical Nutrition, 1990. Body-fat method: Hodgdon & Beckett, US Naval Health Research Center, 1984. Step energy cost: mid-range of published walking estimates (~0.5–0.6 kcal per kg per 1,000 steps).
Calibrate — the trend corrects the estimate
Run your numbers for 2–3 weeks, then compare your 7-day average loss with the pace you picked. For every 0.25 lb/week of difference, move your daily target by ~125 kcal — eat a little less if you're losing slower than planned, a little more if faster. The calculator estimates. The trend decides.
Methodology v1.0 · October 2026 — if a formula ever changes, the version changes with it.
Recommended Books
The short shelf behind the system. Read one, and half the articles here will make even more sense.
The spike-and-crash playbook: food order and simple habits for steadier glucose — and fewer cravings driving the bus.
The insulin-and-fasting case from a Canadian kidney doctor. Read it for the fasting lens — then bring the maths back here.
Why ultra-processed food fights your metabolism and your willpower at the same time.
Sugar treated as a trap, not a character flaw — the mindset method for walking away from it.
Systems over goals. The philosophy this entire site runs on, in book form.
The real science of how your body spends energy — and why the apps overestimate it.
Book links may be affiliate links — they may earn Trendline Fit a small commission at no extra cost to you. Recommendations never change because of it.
Remember
🌙 Sugar roller coasters are real — but every morning you start fresh.
Glucose spikes after dinner are more manageable.
📉 Weight is like the stock market — volatile. Record daily. Trust the week-over-week trend.
Water retention is temporary — and alright.
🕐 First meal when you're really hungry — around 1 PM. Food builds momentum. Start early, spend early.