Cutting-edge smart devices are promising to help you boost fat loss through a simple breath test. Health writer Sarah Sellens checks out the Lumen, which promises to hack your metabolism and help with natural and long-lasting weight loss…

It’s no great secret that metabolic rate – the rate at which you burn nutrients and therefore calories – plays a role in weight loss. Just think of how many times you’ve heard someone blame a few extra pounds on their sluggish metabolism. Or, when you see a slim person eat everything and gain nothing: ‘She’s got a fast metabolism’, we say.

But while you can get a rough estimate of your resting metabolic rate by calculating your basal metabolic rate (BMR), which is the rate at which your body burns calories to stay alive, you can’t accurately measure your metabolism at home – or can you?  

Enter the Lumen, a pocket-sized device that syncs with an app to monitor your metabolic rate. It works as a breathalyser for your metabolism. You breathe into the gadget and it measures the carbon dioxide (CO₂) concentration in your breath.

Why does this matter? Because the results can be used to indicate whether your body is burning carbohydrates or fat for energy. Shifting to a fat-burning state will maximise your weight loss strategies, hence why the ketogenic diet has taken off.

How does the Lumen work?

Sceptical? Interestingly, the premise of the Lumen device isn’t anything new. Indeed, scientists already take breath measurements to calculate the RQ (respiratory quotient) value, or the ratio of carbon dioxide produced by the body to oxygen consumed by the body. This value, presented as a decimal, is used to indicate which macronutrients the body is metabolising. 1.0 indicates that it’s mostly metabolising carbohydrates and 0.7 indicating that it’s mostly metabolising fats.

What’s new is that the Lumen device garners an RQ value in double-quick time. ‘The only way to test metabolism was through a restrictive, hours-long laboratory process,’ explains Michal Mor, co-founder and head of science for Lumen. ‘With Lumen, we are bringing scientifically rigorous insight into personal metabolism for the very first time.’ Basically, it enables you to measure your metabolic rate from the comfort of your home. All within a matter of minutes!

Is the Lumen easy to use?

If you’re feeling a little bit confused by the science, it ultimately doesn’t matter so long as you trust the Lumen device. Smartly, Lumen handles all of the scientific jargon for you and then presents the data on a user-friendly scale. This ranges from one to five, with one indicating that you’re burning more than 84 percent fat, and five indicating that you’re burning more than 80 percent carbs. Teamed with daily dietary plans, the Lumen gadget can help you to optimise your unique metabolic rate swiftly and easily.

So far, so innovative, but how simple is the gadget to use? Actually, it’s pretty straightforward. Initially, you’ll need to allocate some time to setting up your app by adding profile data such as age, height and weight. Next, you’ll have to get to grips with how to breathe into the device. It requires you to inhale, hold your breath, and then exhale gently. This is done through a start-up procedure of five practice breaths. From thereon, it’s more a matter of remembering to use the device at the right times of day: before meals, and also before and after exercise.

While I often remembered my pre-breakfast checks I’ll admit I often struggled to remember to do it again before lunch. However, the number of breaths you take is up to you, but the more breath measurements you do, the more accurate your CO₂ range will be.

Lumen claims a 'single breath' can help you lose weight | Engadget

Does the Lumen tell me what to eat?

While using the device is easy, what is more difficult is following the accompanying diet plan. In the same way that following any nutrition plan can be tricky at times, it takes dedication and can be inconvenient if you’re cooking for others.

The Lumen app provides a daily breakdown of your macronutrient intake, which might be 45g of carbohydrates, 154g of fat and 100g of protein, which an example based on my own data. This macro breakdown is the result of your metabolic profile. This aims to improve what’s called your “metabolic flexibility”, or your body’s ability to switch between burning fats or carbohydrates depending on their availability. The net result of metabolic flexibility is easier weight loss, greater immunity, better sleep, improved health and more. However, you’ll need to be committed, as it involves learning about portion sizes and overhauling your diet somewhat. Fortunately, the app has a handy recipe section, which suggests meals – many of which are rather yummy, having tried them – that roughly fit your diet plan.

Is the Lumen the future of weight loss?

Possibly, but it will cost you a pretty penny to give it a go right now. Pioneering what could be breakthrough technology, the Lumen currently retails at $299 (£228). However, if it really does provide the scientific data of labs and large machines in the way it promises, it’s a worthy investment for those who struggle to lose weight and keep it off, as it reveals in real-time how your body is using energy.

I imagine it will be popular among the keto and general low-carb brigade as it does away with the need to do finger prick glucose blood tests or urine strips to workout ketone levels, as it tells you whether you are burning fat or not. However, the makers say it’s not simply about following a low-carb diet all the time. Instead, it’s a matter of “metabolic flexibility” i.e. being able to transition between fat-burning and carb-burning modes.

The Lumen: is it worth it?

The interesting thing for me, from a sports nutrition and women’s health perspective, was that it reported I needed more carbohydrates when on my period. A woman’s resting metabolic rate increases during this time, which is why you crave carbs and should have a good intake of healthy ones. I followed the app’s guidance and experienced so much more energy than normal during the cycle when I was using Lumen and had fewer energy slumps. While I didn’t lose weight, this was probably because I didn’t use it for long enough (about four weeks). However, I’m certain I would have with more time.

Visit the Lumen website to find out more, to buy your own, or to sign up for a variety of programs based on your health goals.

Click here to discover how the macro diet can help with healthy weight loss!