# CalZen — Complete Reference

> AI-powered calorie counter that tracks nutrition from food photos — 3M+ users on iOS and Android.

CalZen is a mobile app that uses AI to analyze food photos and calculate calories, protein, carbs, and fat in under 3 seconds.

## Key Facts
- Founded in October 2024 by 42apps
- Platforms: iOS (App Store) and Android (Google Play)
- 3M+ users worldwide
- 190K+ ratings with 4.8 average rating globally
- 5M+ food items scanned
- 16 languages supported
- AI-powered: photo recognition with nutrition breakdown in under 3 seconds

## How It Works

1. **Snap a photo** of any meal — home-cooked, restaurant, or takeout
2. **CalZen's AI identifies ingredients**, estimates portions, calculates calories and macros
3. **Your daily calories and macros update automatically** — tracking takes seconds, not minutes

## Key Features

- AI photo-based calorie and macro tracking (no manual entry needed)
- Weight trend tracking with daily progress
- Macro breakdown: protein, carbs, fat
- Water and activity tracking (steps, burned calories)
- Health score based on nutrition balance
- Integrates with Apple Health and Health Connect
- 16 languages supported (EN, DE, FR, ES, IT, PT, NL, PL, NO, SV, DA, JA, KO, ZH, RU, HE)

## Pricing

- 3-day free trial with all premium features
- Monthly: $19.99/month
- Yearly: $49.99/year
- Family Plan: $59.99/year

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## Free Online Tools

### Calorie Calculator for Weight Loss

**URL:** https://calzen.ai/en/calorie-calculator/

Free calorie deficit calculator that uses the Mifflin-St Jeor equation (1990) to estimate daily calorie needs. Includes BMI calculation, macro breakdown, and personalized weight loss programs.

**How to use:**
1. Enter your gender, age, height, and weight
2. Select your activity level (sedentary to extra active)
3. Choose your goal (lose weight, maintain, or gain weight)

**What you get:**
- TDEE (Total Daily Energy Expenditure) in calories
- Calorie targets for weight loss (mild and aggressive deficit)
- Calorie targets for weight gain
- Macro breakdown (protein, carbs, fat in grams)
- BMI with category and health interpretation
- BMR (Basal Metabolic Rate)

**Formulas used:**
- Mifflin-St Jeor (1990): 10×W + 6.25×H − 5×A ± s — most accurate per ADA
- Harris-Benedict (1984, revised): 13.4×W + 4.8×H − 5.7×A + 88.4 (M) — tends to overestimate
- Katch-McArdle: 370 + 21.6×LBM — best for athletes, requires body fat %

Where W = weight (kg), H = height (cm), A = age (years), s = +5 for males, −161 for females, LBM = lean body mass (kg).

**Safe weight loss guidelines (CDC):**
- Recommended loss rate: 0.5–1 kg (1–2 lbs) per week
- Recommended calorie deficit: 500–1,000 kcal/day
- Minimum safe intake: 1,200 kcal/day for women, 1,500 kcal/day for men (NHLBI)

**USDA estimated daily calorie needs by age and activity level:**
- Women 19–25: 2,000 (sedentary) / 2,200 (moderate) / 2,400 (active)
- Men 19–25: 2,400–2,600 / 2,800 / 3,000
- Women 31–50: 1,800 / 2,000 / 2,200
- Men 31–50: 2,200 / 2,400 / 2,800
- Women 51–60: 1,600 / 1,800 / 2,200
- Men 51–60: 2,200 / 2,400 / 2,600

**Calorie Calculator FAQ:**

Q: How many calories should I eat per day?
A: It depends on your age, sex, height, weight, and activity level. Most adults need between 1,600–3,000 calories per day.

Q: Which formula is the most accurate?
A: The Mifflin-St Jeor equation (1990) is considered the most accurate by the Academy of Nutrition and Dietetics. A 2005 systematic review by Frankenfield et al. found it predicts resting metabolic rate within 10% of measured values in more subjects than any other formula.

Q: What is BMR vs TDEE?
A: BMR (Basal Metabolic Rate) is the calories your body burns at complete rest. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by your activity level. TDEE is the number you should use to plan your diet.

Q: How many calories for weight loss?
A: The CDC recommends a deficit of 500–1,000 calories per day for safe weight loss of 0.5–1 kg (1–2 lbs) per week. Never go below 1,200 kcal/day (women) or 1,500 kcal/day (men) without medical supervision.

Q: Should I count calories or macros?
A: Both matter. Total calories determine whether you gain, lose, or maintain weight. Macros (protein, carbs, fat) determine body composition, energy, and health.

Q: What is the minimum safe calorie intake?
A: According to NHLBI guidelines: 1,200 kcal/day for women and 1,500 kcal/day for men. Very low calorie diets (below 800 kcal/day) should only be followed under medical supervision.

Q: Does calorie tracking actually work?
A: Yes. A Kaiser Permanente study (2008) found that people who kept daily food records lost twice as much weight. A 2024 study in JMIR showed that AI-assisted tracking helps 64% of users maintain dietary changes long-term, vs only 23% with manual methods.

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### TDEE Calculator — Total Daily Energy Expenditure

**URL:** https://calzen.ai/en/tdee-calculator/

Free TDEE calculator based on the Mifflin-St Jeor equation. Calculates Total Daily Energy Expenditure for weight loss, maintenance, or muscle gain. Supports three BMR formulas.

**How to use:**
1. Enter your gender, age, height, and weight. Optionally select a formula and enter body fat %
2. Select your activity level (sedentary to extra active)
3. View your complete TDEE results

**What you get:**
- TDEE (Total Daily Energy Expenditure)
- BMR (Basal Metabolic Rate)
- Calorie targets for weight loss and gain at different rates
- Activity level breakdown table
- Macro recommendations (protein, carbs, fat)
- BMI with category and health interpretation
- Ideal weight range
- Comparison across all three formulas

**What is TDEE?**
TDEE (Total Daily Energy Expenditure) is the total number of calories your body burns per day, including all activity. It is calculated by multiplying BMR by an activity factor:
- Sedentary (little/no exercise): BMR × 1.2
- Lightly active (1–3 days/week): BMR × 1.375
- Moderately active (3–5 days/week): BMR × 1.55
- Very active (6–7 days/week): BMR × 1.725
- Extra active (athlete/physical labor): BMR × 1.9

**TDEE vs BMR:**
BMR is the calories your body burns at complete rest — just to keep you alive. TDEE is your BMR plus all additional energy burned through daily activity and exercise. TDEE is always higher than BMR and is the number you should use for diet planning.

**TDEE components:**
- BMR (~60–70% of TDEE): energy for basic body functions
- Thermic Effect of Food (~10%): energy to digest food
- Physical Activity (~20–30%): exercise and daily movement (NEAT)

**TDEE Calculator FAQ:**

Q: What is TDEE and why does it matter?
A: TDEE is the total number of calories your body burns per day. It determines whether you lose, maintain, or gain weight. Eat below your TDEE to lose weight, above it to gain.

Q: How is TDEE calculated?
A: TDEE is calculated by first estimating BMR using the Mifflin-St Jeor equation, then multiplying it by an activity factor (1.2 for sedentary up to 1.9 for very active).

Q: How accurate is the TDEE calculator?
A: The Mifflin-St Jeor equation predicts BMR within ±10% for most healthy adults. Use the result as a starting point and adjust based on actual weight changes over 2–3 weeks.

Q: Should I eat at my TDEE or below it?
A: To maintain weight, eat at your TDEE. To lose weight, eat 300–500 kcal below. To gain muscle, eat 250–500 kcal above with adequate protein and strength training.

Q: Why is my TDEE different from other calculators?
A: Different calculators use different formulas. CalZen uses Mifflin-St Jeor (1990), the most accurate according to a 2005 meta-analysis. Some calculators use the older Harris-Benedict equation, which tends to overestimate.

Q: How often should I recalculate my TDEE?
A: Recalculate whenever your weight changes by 5+ kg, your activity level changes significantly, or every 2–3 months during weight loss.

Q: Can I increase my TDEE?
A: Yes. Increase physical activity (especially strength training), increase NEAT (walk more, take stairs), and eat adequate protein (higher thermic effect). Building muscle is the best long-term strategy.

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## Food Calories & Nutrition Database

**URL:** https://calzen.ai/en/calories-in/

Browse 110+ foods with complete nutrition facts per 100g. Each food page includes calories, macronutrients (protein, fat, carbs, fiber, sugar, water), micronutrients (vitamins and minerals with % Daily Value), a serving size calculator, related foods, and category-specific FAQ.

**Coverage:** 11 categories — fruits (15), vegetables (15), grains (10), meat & poultry (10), fish & seafood (8), dairy (10), nuts & seeds (8), eggs & legumes (6), oils & fats (4), Russian dishes (12), popular foods (12).

**Data sources:** USDA FoodData Central for whole foods; recipe-based analysis for composite dishes.

**Available in 16 languages:** EN, DE, FR, ES, IT, PT, NL, PL, NO, SV, DA, JA, KO, ZH, RU, HE.

**Example pages:**
- Banana: https://calzen.ai/en/calories-in/banana/
- Chicken Breast: https://calzen.ai/en/calories-in/chicken-breast/
- Salmon: https://calzen.ai/en/calories-in/salmon/
- Borscht: https://calzen.ai/en/calories-in/borscht/

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## Scientific References

1. Mifflin MD, St Jeor ST, et al. "A new predictive equation for resting energy expenditure in healthy individuals." Am J Clin Nutr. 1990;51(2):241-7. https://pubmed.ncbi.nlm.nih.gov/2305711/
2. Roza AM, Shizgal HM. "The Harris Benedict equation reevaluated." Am J Clin Nutr. 1984;40(1):168-182. https://pubmed.ncbi.nlm.nih.gov/6741850/
3. Frankenfield D, et al. "Comparison of predictive equations for resting metabolic rate." J Am Diet Assoc. 2005;105(5):775-789. https://pubmed.ncbi.nlm.nih.gov/15883556/
4. USDA. Dietary Guidelines for Americans 2020-2025. https://www.dietaryguidelines.gov/
5. Harvey J, et al. "Log Often, Lose More." Obesity. 2019;27(3):380-384. https://pmc.ncbi.nlm.nih.gov/articles/PMC6647027/
6. CDC. Losing Weight. https://www.cdc.gov/healthy-weight-growth/losing-weight/
7. NHS. Understanding Calories. https://www.nhs.uk/live-well/healthy-weight/managing-your-weight/understanding-calories/

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## Use Cases

- **Weight loss**: Calculate a safe calorie deficit, track food intake by photo, monitor progress with weight trends
- **Muscle gain**: Calculate surplus calories needed, track protein intake, combine with strength training
- **Maintenance**: Know your TDEE, track to stay within range, maintain healthy habits
- **Health monitoring**: Track water intake, monitor macro balance, sync with Apple Health / Health Connect
- **Meal planning**: Understand calorie and macro content of meals before cooking or ordering

## What Makes CalZen Different

- **Photo-first**: No searching databases or manual entry — just snap a photo
- **Speed**: Full nutrition breakdown in under 3 seconds
- **AI accuracy**: ~90% accurate for most meals; "Fix results" feature improves over time
- **Science-based**: Uses Mifflin-St Jeor equation, CDC/USDA guidelines
- **All-in-one**: Calories + macros + water + steps + weight + health score in one app
- **Global**: Available in 16 languages with localized content

## Research on Calorie Tracking Effectiveness

| Study | Finding | Source |
|-------|---------|--------|
| Kaiser Permanente (2008) | People who kept daily food records lost 2× more weight | Am J Prev Med |
| Harvey et al. (2019) | Only 15 min/day of food logging needed for results | Obesity |
| Berry et al. (2021) | Digital self-monitoring = −2.87 kg significant weight loss | Obesity Reviews |
| Huntriss et al. (2024) | 50% of active users achieved 5%+ weight loss | Obesity Sci & Pract |
| AI-Assisted Tracking (2024) | 64% maintain changes vs 23% manual tracking | JMIR |

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## Docs

- [CalZen — AI Calorie Counter](https://calzen.ai/en/): Main landing page with app overview, features, user stories, and download links.
- [Calorie Calculator](https://calzen.ai/en/calorie-calculator/): Free online calorie deficit calculator using Mifflin-St Jeor equation with BMI, macro breakdown, and weight loss programs.
- [TDEE Calculator](https://calzen.ai/en/tdee-calculator/): Free TDEE calculator for weight loss, maintenance, or muscle gain. Supports three BMR formulas with activity level breakdown.
- [Food Calories & Nutrition Database](https://calzen.ai/en/calories-in/): Browse 110+ foods with calories, protein, fat, carbs, vitamins, and minerals per 100g. Data from USDA FoodData Central. 16 languages.
- [CalZen Premium APK — Free Download or Safe Official App?](https://calzen.ai/en/premium/): SEO landing page targeting users searching for cracked/free APK versions. Explains risks of pirated apps and redirects to official stores.
- [Privacy Policy](https://calzen.ai/privacy.html): GDPR/CCPA-compliant privacy policy covering data categories, retention, and user rights.
- [Terms of Use](https://calzen.ai/terms.html): Terms of service for CalZen app and website.
- [Refund Policy](https://calzen.ai/refunds.html): Refund policy for CalZen subscriptions.

## Contact

- Website: https://calzen.ai
- App Store: https://apps.apple.com/app/id6733236996
- Google Play: https://play.google.com/store/apps/details?id=ai.calzen.caloriecounter
- Support: calzen@42apps.io