Lean vs Cronometer. The micronutrient reference vs the only one that recomputes your TDEE continuously.
Cronometer sees your vitamins. Lean sees your real expenditure. Two depths, two promises.
Cronometer calculates your TDEE with Mifflin-St Jeor 1990 (with no bodyfat measured in the app) and a static activity factor picked at signup from 5 boxes (sedentary, light, moderate, heavy, extreme). Cronometer's real strength is elsewhere: the NCCDB database and 80+ micronutrients tracked with a rigor no one else offers in the consumer space. Lean takes a different stance: recompute every component of the TDEE (BMRBasal Metabolic Rate. Energy expended at rest. In Lean, calculated on actual lean mass via BodyScan AI. on real bodyfat via a patented proprietary model, NEATNon-Exercise Activity Thermogenesis. Expenditure from steps and daily activities outside of sport. from steps, EATExercise Activity Thermogenesis. Expenditure from your sport sessions, calculated via MET. via MET, TEFThermic Effect of Food. Energy spent on digestion. Depends on the macros you eat. per macros) and modulate the BMR through metabolic adaptation continuously, with no coefficient to pick.
Cronometer sees your vitamins, not your metabolic adaptation
If you're reading this, you've probably already installed Cronometer. You picked this app precisely because you wanted what no one else offers: tracking of 80+ micronutrients, the NCCDB database stricter than the MyFitnessPal community, weekly vitamin A to K graphs. You entered your weight, height, age, sex, and picked your activity factor from a static list (sedentary, light, moderate, heavy, extreme). The app showed you a calorie target, say 2,250 kcal to lose weight.
You cooked, weighing your ingredients to the gram, because that's what Cronometer requires for the micronutrient graphs to be honest. You checked your vitamin D, your magnesium, your iron, your omega-3. The first 6 weeks, it works. You lose. You're happy. Then around week 8, the scale stalls. You tighten the screws. You drop to 2,000 kcal. Again, nothing moves.
Say Cronometer shows you a TDEE of 2,500 kcal. You eat 2,250 (theoretical deficit of 250 kcal). But in reality, your TDEE has dropped to 2,200 kcal because of metabolic adaptation. You're in a 50 kcal surplus without knowing it. No chance of losing more, even tracking your macros to the gram.
The Cronometer promise is clear and delivered: you know how much magnesium you're taking in. That's valuable. What Cronometer does not do, is recompute your expenditure as weeks of deficit go by. And that's exactly where the "calorie tracker" promise stops, even though it's the lever that actually drives weight loss.
The 1990 BMR formula, with no bodyfat measured in the app
Estimated BMR. Lean's patented proprietary model factors in lean body mass. Mifflin-St Jeor (Cronometer default), does not. A 500 kcal gap, the equivalent of an entire lunch.
To calculate your basal metabolic rate (the BMR, the energy you burn at rest), Cronometer uses the Mifflin-St Jeor equation by default. It's the canonical formula of most consumer calorie trackers, and let's be honest: it's better than the Harris-Benedict 1919 that other apps still use.
Mifflin-St Jeor is from 1990. The sample is larger (498 subjects), the indirect calorimetry methodology is more precise, the formula is calibrated on a more modern population. Cronometer applies the official formula: 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161 (women) or +5 (men).
Good news, Cronometer offers in its advanced settings an option Katch-McArdle which does factor in lean body mass. The catch: Katch-McArdle requires you to enter your bodyfat manually. DEXA scan, skinfold caliper, bioimpedance scale, or visual estimation. No measurement built into the app. The vast majority of Cronometer users therefore stay on Mifflin by default, for lack of an accessible reliable bodyfat value.
Mifflin (1990) marginally improves on Harris-Benedict (1919) for average accuracy, but inherits the same conceptual flaw: the formula only accounts for weight. Not bodyfat. Not lean mass.
Yet since the 1980s, we've known that fat mass burns very little energy compared to the rest of the body. The liver, brain, heart, kidneys, and especially muscles are the real energy sinks. Fat mass is inert. Someone at 30% bodyfat does not burn anywhere near as much as someone at 10% bodyfat, even at identical weight.
Frankenfield 2013 (PubMed 23631843) compared Mifflin-St Jeor to reference indirect calorimetry across obese and non-obese cohorts. Result: 87 % accuracy in non-obese subjects, and only 75 % in obese subjects. A more recent study (PMC11820646) shows that for BMIs above 35, Mifflin is off by 250 to 315 kcal per day. That’s a full snack’s worth of error in your deficit calculation.
500 kcal is not nothing. If Cronometer tells you "your BMR is 2,500" and in reality it's 2,000, everything that follows is wrong: your deficit target, your weekly loss projection, your macro split calculated as a percentage of TDEE.
Partial conclusion: if an app computes your BMR using only your weight, height, age and sex, the result cannot be individualized. It’s mathematically impossible.
The activity factor, picked once and for all
This is where it gets serious. And it’s probably the point nobody ever explained to you.
Once Cronometer has calculated your BMR (with no bodyfat measured in the app), it has to estimate your total TDEE. The TDEE is BMR plus everything else : expenditure from steps, daily activities, sport, and digestion. Everything that isn't basal metabolism.
How does Cronometer do this ? It asks you, only once at signup, to pick your activity factor from a static list. These factors are called in sports science PAL levels (Physical Activity Level), it’s just a multiplier applied to your BMR:
- Sedentary (PAL 1.2): desk job, little walking
- Light Activity (PAL 1.375): occasional walking
- Moderate Activity (PAL 1.55): sport 3 to 5 times a week
- Heavy (PAL 1.725): intense sport almost daily
- Extreme (PAL 1.9): very intense sport or physical labor
And depending on your choice, the app multiplies your BMR by the matching coefficient. That's it. That's all there is behind your daily calorie target. A box YOU ticked only once at signup. Often six months ago. Untouched since.
And here’s the silent trap: this approximation is wildly imperfect. The difference between a day stuck on the couch watching Netflix and a day at Disneyland walking 15 km with your kids over 1,000 kcal. None of the 5 boxes captures that.
Cronometer syncs well with Apple Health and Google Fit, and pulls in your steps. The "active mode" can add an exercise expenditure estimate to your daily calorie target. But these steps do not feed a full TDEE recompute: your calorie target stays based on the activity factor picked at onboarding, plus an exercise add-on that blurs NEAT and EAT together, without properly separating them.
Real expenditure measured over 7 days for a Lean user. The grey line is what Cronometer was showing (2,400 kcal flat, PAL Moderate × BMR). The pink annotations show why each day moves.
You can’t reduce your activity level to a static box. You might be active in weeks when you barely work from home, and sedentary in weeks when you never leave the office. You might be active in summer and sedentary in winter. You might be active from Tuesday to Friday and sedentary on weekends.
Which box are you going to tick this week? The truth is, none of the 5 will be correct. And so Cronometer will give you a TDEE that will systematically be disconnected from reality.
The key point of this article: even if Cronometer had a perfect BMR formula (Katch-McArdle properly filled in), the static PAL would be enough to break everything. You can't estimate a NEAT, EAT and TEF with a single multiplier on top of BMR. Conceptually absurd.
You get the idea: a BMR formula with no bodyfat measured in the app, plus a static PAL approximation of the other expenditure components, gives very little chance of hitting your goals over 3 to 6 months.
Metabolic adaptation, never modeled
This is the final boss. The most subtle concept. And probably the most important.
When you’re in a calorie deficit, your body realizes it’s receiving less energy than before. To protect itself, it switches to power-saving mode. Exactly like your iPhone’s low-power mode: everything keeps working, just using less energy. Your BMR drops. Your NEAT drops. Your EAT drops.
This is called metabolic adaptation. The scientific literature is clear and reproducible: Müller 2015 (PubMed 26399868, Minnesota revisit), Doucet 2001 (PubMed 11430776), Nunes 2020 (PMC7484122) over 6 weeks of deficit. Here are the numbers:
- Deficit of −250 kcal per day, over 2 to 8 weeks: adaptation of 5 to 10% (TDEE drops to 90-95 % of the initial level)
- Deficit of −500 kcal per day: 10 to 15% adaptation (TDEE drops to 85-90 %)
- Deficit of −750 kcal per day: 15 to 25% adaptation (TDEE drops to 75-85 %)
Lean convention: 100 % = optimal, 90 % = 10 % adaptation. And since NEAT, EAT and TEF all depend directly on the BMR, almost the entire TDEE is impacted.
real TDEE over 8 weeks of deficit at −500 kcal/day. The pink curve drops. The Cronometer line stays flat. By week 6, you're already at maintenance. Without having changed anything.
Concretely: if you planned a 10 % deficit on a TDEE of 2,500 (eating 2,250 per day), and your body adapts by 10 %, your real TDEE has dropped to 2,250. You’re at maintenance. You stop losing.
The trap is how insidious it is. At first, you lose weight. You’re happy. You keep going. But week after week, the adaptation stacks. And at some point, without changing anything in your tracking, you stop losing.
95% of people go through this without understanding. They blame their willpower. They blame their "broken metabolism". They jump into harsher diets, which makes adaptation worse. Spiral.
Cronometer never calculates metabolic adaptation. It gives you a fixed, static calorie target as long as you don't manually update your weight and activity factor. You can see your magnesium week after week with surgical precision, but when you stall after 6 weeks of cut, the app has no idea why.
How Lean fixes each of the 3 problems
Lean was not built as an improved Cronometer clone. Cronometer has 12 years of head start on micronutrients and there's no reason to catch up on that turf. Lean was built for the complementary angle: seriously tracking the full TDEE theory (BMR + NEAT + EAT + TEF), with metabolic adaptation as a 5th brick that modulates the BMR continuously. Concretely, here is how Lean handles each component.
Proprietary patented model, built on lean mass
Lean uses a proprietary patented model which depends directly on lean mass, not raw bodyweight. To do that, the app needs your bodyfat. And here we hit the historically painful problem: how do you measure your bodyfat without paying for a clinic DEXA scan every week?
Lean’s answer: the BodyScan AI. You take a photo, the app runs it through a model trained on a massive bank of DEXA scans, and you get your estimated bodyfat in seconds. You can redo it every week. The BMR recomputes automatically.
Goodbye skinfold calipers (imprecise), goodbye bioimpedance scales (unreliable), goodbye DEXA scan (perfect but not accessible weekly). One photo, 5 seconds.
NEAT, EAT, TEF calculated separately
NEAT. Lean pulls your real step count via HealthKit (iOS) or Google Fit (Android). No declaration. No “I think I walk enough.” Your steps, measured by your smartphone’s very precise accelerometers. The NEAT is computed by crossing those steps with your BMR, every day, with no coefficient to pick.
EAT. For each training session, you pick the sport from a list (strength training, running, tennis, swimming, etc.), and Lean uses the sport’s MET (Metabolic Equivalent Task) to compute the real expenditure. You enter the actual time effective of sport (not the total time with rest periods: the mistake 100 % of smartwatches make). A strength session at 1,050 kcal according to your Apple Watch? Reality is closer to 200 kcal. Lean refuses that drift.
TEF. Digestion burns energy, and it isn't a flat 10% lump. Protein costs 20 to 30% of their calories in digestion. Carbs 5 to 10 %. Fats 1 to 3 %. Lean computes your real TEF from your macros. At 3,000 kcal/day, that can be a 100 kcal gap depending on your diet composition.
A world first on a consumer app
Lean is, to our knowledge, the first app to compute metabolic adaptation automatically. As your weeks in deficit add up, the app adjusts your TDEE downward based on the scientifically established figures (Müller 2015, Doucet 2001, Nunes 2020). Convention 100 → 0 %: 100 % = optimal, 90 % = 10 % adaptation. You don’t have to do anything. You see your calorie goal readjust gently, with no surprises.
When you hit 10 to 15 % adaptation, the app can recommend a return to maintenance to reset your BMR before going back into deficit. Cycle, plateau, cycle. Just like in serious protocols.
No activity coefficient to pick. No static PAL box. Just every component computed precisely, week after week.
Lean vs Cronometer, criterion by criterion
An honest read of each app's strengths and weaknesses. No criterion touches price.
3 ways to track a meal
Tracking calories is fine. Doing it for 12 months is another story. Principle #1, before science, before macros, before everythingis adherence. If the tracking method annoys you, you quit after 3 weeks. Lean offers 3 ways to log a meal:
- Database search. Curated base, USDA + OpenFoodFacts. No community noise, no "Roast chicken" entered 47 times by 47 different users with 47 different values.
- Barcode scan. Standard. You scan your pasta box, you get the macros.
- AI photo scan of a meal. You photograph your plate, the AI detects the foods, you get the calories and macros per food.
The AI photo scan is the adherence game changer. When you eat out, at a restaurant, at friends’, it’s extremely practical. One photo, you close the app, you enjoy your evening. Yes, it’s less accurate than weighing to the gram with a kitchen scale. But over 12 months, that’s what makes the difference between sticking with it and giving up. And sticking with it is what counts.
Beyond meal-by-meal tracking, Lean shows a live TDEE that updates throughout the day. The more you walk, the more your expenditure rises, the more your daily calorie goal adjusts. You see your calorie balance live. It’s more motivating than a number frozen at 8 a.m.
And above all that sits the Progression Pyramid. It’s an app screen that ranks what matters:
What Cronometer does better
Lean is not perfect, and Cronometer has several real strengths that must be acknowledged. Honest read, criterion by criterion, on the axes where Cronometer stays ahead. None of these axes are secondary: they are real pillars of the Cronometer promise.
Honest read. On micronutrients, Cronometer is the absolute reference: 80+ vitamins, minerals, omega-3/6, essential and non-essential amino acids, with DRI/RDA percentage display and trend graphs. No other consumer app comes close to this depth. Lean shows macros and calories, that's it. On the food database, Cronometer relies on NCCDB (the most rigorous database on the consumer market, hand-curated by their team), plus USDA and IFNDC. Lean relies on USDA and curated OpenFoodFacts, which covers daily uses well but does not go as deep on the quality of exotic entries or processed products. On professional adoption, Cronometer is used by a huge number of registered dietitians (RDs) and sports coaches as a reference tool for the weekly micronutrient review of their clients.
If your main angle is micronutrient optimization (pre-competition, demanding restrictive diet like vegan or keto, iron/B12/D deficiency prevention), or if you need a tool that your RD or coach can audit in a consultation, Cronometer is more relevant than Lean. If your angle is the precision of the TDEE calculation, the bodyfat measured every week via BodyScan AI, and automatic metabolic adaptation, that's exactly what was just demonstrated in the previous 3 sections. Many advanced users run both apps in parallel, and that's entirely defensible.
Who Lean is built for
4 profiles. If you recognise yourself in at least one, Lean is probably built for you.
You used Cronometer seriously and you didn't lose
You weighed your ingredients, checked your micronutrients, ran an honest deficit for weeks, and you're stalling. Cronometer isn't the culprit, the frozen TDEE from Mifflin without bodyfat is. Lean fixes it at the root via a BMR on real bodyfat.
You plateau after several weeks of cutting
Plateau that drags on after 4 to 8 weeks. That’s metabolic adaptation. Lean computes it automatically and readjusts your goal every week.
You want to understand your metabolism
Lean shows each component (BMR, NEAT, EAT, TEF) and explains adaptation separately, instead of hiding everything behind a single number. You see where every kcal of expenditure comes from.
You want tracking that lasts 12 months
AI photo scan + curated database + barcode cover every use case, from raw ingredient to restaurant pizza. That's what makes the difference between sticking with it and giving up.
Cronometer remains more relevant for : deep micronutrient tracking (vitamins, minerals, omegas, amino acids), restrictive diets (vegan, keto, low-FODMAP) where deficiency prevention is critical, or the shared review with your registered dietitian (RD). TDEE precision and metabolic adaptation just aren't part of its main promise.
Switching from Cronometer to Lean (or using both) in 3 minutes
Download Lean
App Store or Play Store. Sign-up in 30 seconds.
BodyScan AI
One photo, 5 seconds. You get your bodyfat.
Weight & height
You enter your weight and height. That’s it.
Lean computes
BMR on real bodyfat, NEAT via HealthKit / Google Fit (real steps), EAT via MET, TEF via macros, plus metabolic adaptation that modulates the BMR. Automatic.
Log a meal
Photo, barcode or database. You get the flow.
Important note. Lean does not import your Cronometer history automatically, nor your custom foods. If you want to keep a weekly micronutrient check in parallel, many advanced users keep logging 1 or 2 days a week in Cronometer for the vitamin check, while using Lean daily for the TDEE and the main tracking. The HealthKit / Google Health Connect sync, on its side, takes over immediately for your steps and your activity history.
What Lean does, that Cronometer does not (on the TDEE)
Six features that exist in no other consumer tracker. They all come from the same principle: compute every TDEE component precisely, not approximate it.
Your real bodyfat, measured from a single photo, redone every week. The data point that flips the entire BMR calculation. No other consumer app offers this.
Track your restaurant meal in 2 seconds. No scale, no manual entry. The adherence game-changer over 12 months.
Your TDEE re-adjusts week after week following the scientifically established numbers. You avoid the plateaus nobody can explain.
BMR + NEAT + EAT + TEF each shown, updated throughout the day. No more frozen 8am number. You see your calorie balance live.
Track weight, bodyfat, lean mass trends over months. Understand your cycles. Spot the phases where you progress and the ones where you stall.
Photo, barcode, curated database. No other app offers all three with this level of precision. You pick the method based on context.
You install the app for free, you try it without commitment, then you decide if the tool fits your goal.
Frequently asked questions
Cronometer is the micronutrient reference, why compare it to Lean on the TDEE ?
Why doesn't Cronometer calculate the BMR on real bodyfat by default ?
Does Lean track micronutrients like Cronometer ?
Cronometer imports steps via HealthKit, is that enough for NEAT ?
Is Lean free or paid?
Can you use Lean and Cronometer in parallel ?
1990 vs 2026
This isn't Cronometer vs Lean in marketing. It's micronutrient depth vs TDEE precision, two different promises.
Cronometer stays the best app to track your 80+ micronutrients, and no one in the consumer space does better. But for your TDEE, Cronometer uses Mifflin-St Jeor 1990 without bodyfat measured in the app (Katch-McArdle exists but requires manual bodyfat entry), plus a frozen activity factor you tick only once at signup (sedentary, light, moderate, heavy, extreme), and ignores metabolic adaptation. The combo of the three makes any precise calorie tracking impossible beyond a few weeks of cut. It's mathematical.
Lean was built to do the exact opposite: BMR based on real bodyfat (measured by BodyScan AI) via a proprietary patented model, NEAT from real steps, EAT per sport via MET, TEF from macros, plus metabolic adaptation that modulates the BMR week after week. Every component computed precisely, with no magic coefficient.
Cronometer stays very solid on micronutrients and the quality of its NCCDB food database. If you tried Cronometer seriously and didn't get the cut results you hoped for, the problem isn't you, nor Cronometer on its micronutrient promise. The problem is the TDEE frozen under the hood. Change the engine, keep the instrumentation if you need it in parallel.
Lean is available as a free download
iOS and Android. The BodyScan AI works from a single photo. No skinfold calliper, no bioimpedance scale, no DEXA.
Internal links
- Free online TDEE calculator · web version, no sign-up, same logic as the app (BMR + NEAT + EAT + TEF).
- Understand TDEE in depth (BMR, NEAT, EAT, TEF, adaptation) · deep-science article.
- How to count your calories properly · practical guide for beginners.
- NEAT: expenditure from steps and non-exercise activity.
- TEF: digestion burns calories.
Bibliography
- Harris J.A., Benedict F.G. (1919). A Biometric Study of Basal Metabolism in Man. Carnegie Institution of Washington.
- Mifflin M.D. et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition.
- Katch V.L., McArdle W.D. (1973). Prediction of body density from simple anthropometric measurements in college-age men and women. Human Biology.
- Frankenfield D.C. et al. (2013). Validation of Mifflin-St Jeor equation in obese and non-obese populations. PubMed 23631843.
- Westerterp K.R. (2004). Diet induced thermogenesis. Nutrition and Metabolism.
- Müller M.J., Bosy-Westphal A. (2013). Adaptive thermogenesis with weight loss in humans. Obesity.
- Schakel S.F., Sievert Y.A., Buzzard I.M. (1988). Sources of data for developing and maintaining a nutrient database (NCCDB). Journal of the American Dietetic Association.
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