Best Weight Loss Apps: What They Do and What the Evidence Shows

Weight loss apps have become one of the most searched tools for people starting a calorie deficit. The market is large and the claims are loud — but what do the apps actually do, and what does the evidence say about whether they help? This guide cuts through the noise and explains what to look for, what matters, and what the science shows.

What Weight Loss Apps Actually Do

Before evaluating which app is best, it helps to understand what category of problem they solve. Most apps marketed as "weight loss apps" fall into one of three types:

Calorie and macro tracking apps are the most evidence-backed category. They provide a food database, logging interface, and daily calorie/macro targets. You log what you eat; the app calculates your intake against your target. Examples: MyFitnessPal, Cronometer, Lose It!, Nutracheck, MyNetDiary. These are tools for measurement accuracy, not weight loss in themselves.

Behaviour change and coaching apps focus on habit formation, accountability, and psychological support rather than food logging. Examples: Noom, Lasta, Second Nature. These typically combine some food tracking with educational content, check-ins, and coaching elements. The weight loss mechanism is still calorie deficit; the app attempts to create the conditions for sustained adherence.

General wellness and fitness apps (MyFitnessPal's fitness tracking, Apple Health, Garmin Connect) track exercise and activity but do not primarily focus on food intake. They're useful as companions to calorie tracking but are not weight loss tools by themselves.

Understanding which category you're evaluating matters because the evidence base is different for each.

What the Evidence Shows

The research on app-assisted weight loss is reasonably consistent: people who use calorie tracking apps lose more weight than people who don't.

A 2019 systematic review and meta-analysis published in the Journal of Medical Internet Research found that smartphone app use for weight management was associated with significantly greater weight loss compared to control groups — an average of approximately 1.04 kg additional loss. More intensive app-based interventions (with coaching, reminders, and logging support) produced larger effects.

A 2021 review in Obesity Reviews found consistent evidence that self-monitoring via apps (food diaries, activity tracking) improved weight loss outcomes, with the strongest effects in studies where participants logged consistently over time.

The important caveat: the evidence is for consistent use, not for downloading an app. The weight loss mechanism is the calorie deficit the app helps you create and maintain — not anything the app does independently. Apps that make consistent logging easier produce better outcomes because people actually use them. Apps with steep learning curves, poor databases, or friction-heavy interfaces tend to be abandoned within weeks, producing no benefit.

For behaviour change apps like Noom, the evidence is thinner. A 2016 study published in Scientific Reports found meaningful weight loss in Noom users over 18 months — but the study was conducted by Noom and lacked a randomised control group. Independent evidence for coaching-style apps producing results beyond good calorie tracking apps is limited.

The Most Important Features to Look For

Not all apps are equally usable. The features that predict whether an app will work for you long-term:

Database size and accuracy. The single most important feature of any calorie tracking app. A food database with millions of entries allows you to find almost any food quickly. MyFitnessPal's database is the largest (300+ million entries) but has significant accuracy problems — user-submitted entries are unverified and frequently wrong. Cronometer uses verified USDA/government nutrient data and is substantially more accurate, particularly for micronutrients. Nutracheck's UK-specific database is well-verified for UK branded foods. If you're tracking macros carefully, database accuracy matters more than size.

Barcode scanning. Scanning a product barcode and having it populate automatically is a significant friction reducer for packaged foods. All major apps offer this, but the quality varies — some apps resolve scans to user-submitted entries that may contain errors, while others prioritise manufacturer-verified data.

Macro breakdown and custom targets. If you're tracking protein as well as calories (strongly advisable for most weight loss approaches), you need an app that displays protein, fat, and carbohydrate clearly and lets you set custom macro targets rather than just using generic percentages. Cronometer and MyFitnessPal both allow this; some simpler apps don't.

Recipe builder and meal planning. The ability to log a homemade meal by entering its ingredients is essential if you cook regularly. Apps with a clunky recipe builder make home cooking logging tedious enough to abandon. Check the recipe flow before committing.

Food scale integration. The most accurate tracking requires weighing food, not estimating. Apps that allow you to log by weight in grams (rather than forcing you into ambiguous serving size descriptions like "1 cup" or "1 medium") are more accurate and produce better outcomes. A food scale paired with an app that accepts gram-weight entries is the highest-accuracy combination available. See our food scale buying guide for recommendations.

Ease of repeat logging. Most people eat similar meals repeatedly. Apps that let you save meals, recall recent foods instantly, or log a saved meal in one tap dramatically reduce the daily time investment. This is one of the strongest predictors of whether someone will keep logging after the first two weeks.

Free vs Paid: What You Actually Get

Most major apps have a free tier that covers the core calorie tracking functionality:

App	Free tier	Paid tier adds	Cost (approx)
MyFitnessPal	Calorie + macro tracking, large database, barcode scan	Macro goal customisation, ad-free, guided plans	~£17/month or £54/year
Cronometer	Calorie + full micronutrient tracking, verified database, barcode scan	Trend graphs, custom biometrics, ad-free	~£3/month
Lose It!	Calorie tracking, basic macro view, barcode scan	Macro breakdown, meal planning, exercise tracking	~£26/year
Nutracheck	Limited (7-day trial only)	Full UK food database, barcode scan, reports	~£4/month
Noom	None — subscription only	Coaching, behaviour change curriculum, food logging	~£45-70/month

For most people, the free tier of MyFitnessPal or Cronometer provides everything needed to track calories and macros accurately. Paid tiers add convenience features — they're worth considering if you find the free tier friction points disruptive, but they're not required for the core tracking function.

Noom's price point is only justified if the coaching and accountability elements are genuinely what you need — and if so, working with a registered dietitian directly may provide more personalised and evidence-based support for a comparable or lower cost.

What Apps Can't Do

This is the critical point most app marketing obscures: an app does not create a calorie deficit. You do.

An app is a measurement tool. It tells you how many calories you've consumed if you log accurately. The deficit comes from eating less than your maintenance level. The app helps you know whether you're doing that — it doesn't cause weight loss independently.

Two things determine whether app-assisted tracking actually works:

Logging consistency. An app used intermittently produces data that looks complete but systematically underestimates intake (because the meals that don't get logged are often the higher-calorie ones). The research on tracking accuracy consistently shows that consistent daily logging is what produces outcomes, not occasional tracking.

Input accuracy. App tracking is only as accurate as what goes into it. Estimating "1 cup of pasta" instead of weighing 80g introduces errors that compound across meals. People who use a food scale for high-error foods (oils, grains, nuts) are 2-3x more accurate than those who estimate. See our portion sizes guide for the specific foods where estimation goes most wrong.

The apps that produce the best real-world outcomes are the ones people actually use consistently and input accurately — not necessarily the ones with the most features.

Which App for Which Goal

For calorie tracking with high accuracy: Cronometer. Verified database, full micronutrient data, gram-weight entry, and a paid tier that's inexpensive. Best choice for people who want precision and are tracking protein closely.

For the largest food database and fastest logging: MyFitnessPal (free tier is sufficient for most). The database size means you can find almost anything instantly, and the repeat-meal logging is among the best available. Be aware of database accuracy issues for specific entries — when in doubt, cross-reference with Cronometer or the nutrition label.

For UK users tracking branded foods: Nutracheck. The UK-verified food database is substantially more accurate than MyFitnessPal's UK entries, which are often user-submitted and unreliable for UK products.

For macro-focused tracking (protein, fat, carb targets): Cronometer or MyFitnessPal premium. Both allow custom macro targets and clear per-meal breakdowns. See our macro tracking guide for how to set macro targets effectively.

How to Set Up an App to Actually Work

Most people who abandon calorie tracking do so because the setup friction compounds over the first two weeks until the habit collapses. A clean setup on day one prevents most of this:

1. Set your calorie target first. Don't trust the app's default calculation — use an accurate TDEE estimate based on your current weight, height, age, and activity level, then subtract 300-500 calories for a sustainable deficit. See our calorie deficit guide for how to calculate this.
2. Set protein target explicitly. Most app defaults set protein too low. A target of 1.6-2.2g per kg of bodyweight is the evidence-based range for weight loss with muscle preservation.
3. Log everything for the first two weeks. Including cooking oils, condiments, drinks, and "tastes." These are where the gap between tracking and reality usually lives.
4. Use weight entries, not volume. Log 15g olive oil, not "1 tablespoon." Log 80g dry oats, not "1 cup." Volume entries have too much variance to be reliable.
5. Save your frequent meals immediately. After logging a meal, save it. Within a week you'll have a library of your actual regular meals that log in seconds.
6. Weigh yourself weekly, log the trend. Daily weight fluctuates by 1-2kg from water and digestion — weekly averages remove the noise and show the real trajectory.

Summary

• Calorie tracking apps are measurement tools — they help you know whether you're in a deficit; they don't create the deficit themselves
• Evidence shows app users lose approximately 1kg more than non-users on average; the effect requires consistent daily logging, not just having the app
• For accuracy: Cronometer (verified database, best for precision); for database size and speed: MyFitnessPal; for UK branded foods: Nutracheck
• Key features: database accuracy, barcode scan, gram-weight entry, easy repeat logging, macro targets
• Free tiers of Cronometer and MyFitnessPal cover everything most people need — paid tiers add convenience, not fundamental capability
• Apps fail when logging is inconsistent or uses estimates instead of weights — a food scale paired with any major tracking app is the highest-accuracy combination available

---

Related Reading

• Why Am I Not Losing Weight on a Calorie Deficit? A Troubleshooting Guide
• Calorie Deficit for Beginners — How to Calculate Yours and Actually Maintain It
• How to Count Macros for Weight Loss — A Beginner's Complete Guide
• Portion Sizes Explained — A Visual Guide to How Much You're Actually Eating
• Best Food Scale for Meal Prep — Top Picks for Accurate Tracking

Download our portion guide

Start tracking your food today

Gut Health and Weight Loss: How Your Microbiome Affects Fat Loss and What to Do

How Stress Causes Weight Gain: The Cortisol Mechanism Explained

How to Lose Weight With Type 2 Diabetes: What the Evidence Shows