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What RDs Need to Know About Lumen
By Carrie Dennett, MPH, RDN
Tech companies have been moving steadily into the health, wellness, and nutrition space, with one entrant to the field, Lumen, in particular, billed as “the first device to hack your metabolism.” The claim is that the device will help people burn fat, lose weight, boost energy, and improve overall health. But are those claims backed by evidence, and if they are, is this “metabolism breathalyzer” right for everyone?
Lumen’s overarching claim is that it helps users improve “metabolic flexibility,” optimizing the body’s ability to burn fat and making the body more efficient in shifting between using fat or carbohydrates for energy. Lumen’s website states that metabolic flexibility is achieved by improving mitochondrial function and insulin sensitivity through manipulating carbohydrate intake, exercising in the morning—when carbohydrate levels and glycogen stores are low—and engaging in time-restricted eating.
Users breathe into the Lumen device, which measures carbon dioxide levels in the breath. The device app indicates whether users are currently using carbs or fat for fuel and provides a score for how flexible their metabolism is based on two weeks of data, then offers recommendations for diet, exercise, and sleep.
The website also states that peer-reviewed research has validated that Lumen is the “gold standard of measuring metabolism.” Of the three peer-reviewed studies on Lumen, one is a pilot study,1 one concluded that Lumen performs as well as a metabolic cart,2 and one was a very short, very small device-validation study.3 None support the company’s weight loss or health claims, and all were funded and conducted by Lumen’s parent company, Metaflow.
The device is $299, or $527 with a one-year membership—which includes the personalized recommendations—after which the membership is $159 per year. But costs aside, who needs a “metabolism breathalyzer,” and who specifically should avoid it?
“Metabolism has become a buzzword that’s typically thrown around in the discussion of weight loss,” says Abby Chan, MS, RDN, RYT, co-owner and nutrition director of EVOLVE Flagstaff in Arizona. “But when we look at metabolism, it’s a complex chemical process that’s determined by genetics, organ function, allostatic load (stress), body composition, and other environmental factors.” She adds that Lumen’s “personalized” recommendations look more like general boilerplate nutrition recommendations that fall in line with the current low-carb, intermittent fasting trends touted by Instagram influencers.
“A metabolism breathalyzer is another type of tracker and may provide more in-depth information that could be helpful to some people,” says Seattle-based Ginger Hultin, MS, RDN, CSO, owner of Ginger Hultin Nutrition and author of Anti-Inflammatory Diet Meal Prep. “I wouldn't recommend it as a first stop for any of my patients.”
Benefits and Risks
Lauren Harris-Pincus, MS, RDN, Basking Ridge, New Jersey-based founder of NutritionStarringYOU.com and author of The Everything Easy Pre-Diabetes Cookbook, says people with a tech fascination and time and money to spare may find the device interesting and informative, but there are downsides. “Users need to be comfortable tracking and counting macronutrients and also require flexibility in their daily eating plans,” she says. “If you meal-prep for the week and your morning breathalyzer results tell you to consume a higher or lower-carb diet for the day, it may conflict with your routine.”
Chan, who’s also a long-time strength coach and athlete, says she often encourages her clients to pay more attention to what their bodies are saying rather than take a device’s data as fact. She notes that clients who are neurodivergent and have difficulty paying attention to internal cues may find some of the data provided by Lumen a helpful starting point for making more mindful decisions—but also could gain much of this insight by working with a dietitian who can take their personal health history, food preferences, and culture into consideration. “I’m always excited about new health-related technology,” Chan continues, “but I feel that a device like this has a long way to go to provide actual personalized and culturally sensitive information that doesn't negatively impact someone's relationship with food and their body.”
Hultin says some of her clients thrive by using tools and trackers. “For some personalities, though, these can become obsessive and can drive disordered behavior or a negative relationship with food and body,” she says. “Having to track what you eat so specifically or think about nutrition so intensely every day, all the time, can be exhausting and overwhelming.”
Counseling Lumen-Curious Clients
What questions should dietitians ask if clients express interest in using Lumen? Harris-Pincus says she would ask what they hope to gain from using the device and if they’re prepared to commit to following dietary recommendations that change daily—and if tracking their food will affect their relationship with and enjoyment of food.
Hultin says she’d also ask clients whether they understood what the device was testing and how it works, and whether the intense focus on using the device and tracking food is compatible with their other life demands. “I'd also ask about their goals,” she says. “Is there work we can do together even without the device, such as balancing meals better or adjusting recipes or meal timing, that I know will help them? I'm very open minded to exploring new tools that my clients want to use, but it has to be the right fit and timing.”
— Carrie Dennett, MPH, RDN, is the nutrition columnist for The Seattle Times, owner of Nutrition By Carrie, and author of Healthy for Your Life: A Non-Diet Approach to Optimal Well-being.
References
1. Buch A, Yeshurun S, Cramer T, et al. The effects of metabolism tracker device (Lumen) usage on metabolic control in adults with prediabetes: pilot clinical trial. Obes Facts. 2023;16(1):53-61.
2. Roberts J, Dugdale-Duwell D, Lillis J, et al. The efficacy of a home-use metabolic device (Lumen) in response to a short-term low and high carbohydrate diet in healthy volunteers. J Int Soc Sports Nutr. 2023;20(1):2185537.
3. Lorenz KA, Yeshurun S, Aziz R, et al. A handheld metabolic device (Lumen) to measure fuel utilization in healthy young adults: device validation study. Interact J Med Res. 2021;10(2):e25371.