Lumen

Lumen is the handheld metabolism tracker that measures whether you are burning carbs or fat and tells you what to eat.

Overview

Lumen measures your metabolism through your breath: a quick exhale into the device analyzes CO2 levels to determine whether your body is primarily burning carbs or fat. Its app then gives nutrition and workout guidance for the day ahead.

The device’s machine-learning models adapt recommendations to sleep, exercise and cycle data, aiming for metabolic flexibility rather than fixed dieting. For users who want physiology-based nutrition guidance without lab testing, Lumen brings metabolic measurement home.

Nutrition advice is usually generic because measuring metabolism requires lab equipment — until a handheld device could read it from your breath. Lumen measures CO2 concentration to determine whether your body is currently burning carbs or fat, then gives daily guidance on eating and training to move toward metabolic flexibility. The models adapt to sleep, exercise and cycle data, so recommendations change with your context rather than following a fixed plan. For users tired of calorie counting without physiological feedback, the device offers something different: measurement-based nutrition at home. The trade-off versus clinical testing is precision, but daily usability is where behavior actually changes.

Daily measurement builds the awareness that generic plans cannot: users learn how their own bodies respond to meals, sleep and training, and guidance improves as the device gathers more context.

The strongest apps in this category translate data into daily decisions — what to do today, how hard to push, when to rest — rather than leaving users to interpret raw metrics on their own.

Key Features

• Breath-based metabolic measurement in seconds
• Daily carb-versus-fat burn status readings
• Personalized nutrition and workout recommendations
• Adaptive guidance using sleep, activity and cycle data
• Metabolic flexibility tracking over time
• Compact handheld device with companion app

Pricing

Lumen is purchased as hardware with the app experience included; some premium plans add coaching features.

Who Is It For

Health-conscious users who want physiology-based nutrition and training guidance at home. Also fits endurance athletes tuning nutrition around training load and metabolic state, and to users who prefer measurement-based guidance over generic diet rules.

FAQ

Is Lumen free to use?

The device is a purchase; core app functionality is included with optional paid coaching.

Does Lumen offer an API?

Lumen integrates with health platforms; a broad public developer API is not the focus.

How does Lumen compare to alternatives?

Compared with food-logging apps, Lumen measures metabolism directly; compared with lab testing, it trades clinical precision for daily convenience.