Low carb, high carb, keto, intermittent fasting, Mediterranean diet, there’s a lot of nutritional noise about the best foods to stick in our cake (or kale) holes to optimize our health and fitness. .
But when we’re all built differently, with different individual goals and needs, are unique diets really our best bet? Or is there a smarter way to get the right balance of carbohydrates, fats and proteins, at the right time?
Maybe there are. Breathe into Lumen’s portable breathalyzer and it will sniff the CO2 levels in your breath, to instantly reveal whether your body is burning fat, carbs or both, then make personalized recommendations. It also reveals how efficiently your body switches between carbohydrates and fats as a fuel source, i.e. your metabolic flexibility.
Armed with this real-time information, you can make smarter choices about what to eat and when to eat it. Like spotting when you have enough energy on board for your next workout or when you need to refuel. The partner app also offers personalized daily macro-nutrition plans to boost your fuel-shifting powers.
A closer look at science
There are potentially big benefits to improving your metabolic health: including weight loss, maintaining healthy body composition, stabilizing blood sugar, and improving insulin sensitivity. It can also provide more energy for work and workouts, not to mention prevent diabetes and other metabolic diseases.
“Metabolic flexibility is important,” says Matt Gardner, body composition and fitness testing consultant at MyVitalMetrics. “Some people who are more metabolically flexible may find that they can maintain a desired weight or lean body mass for longer.”
“Metabolic flexibility can also contribute to better endurance performance. If you can burn a little more fat at moderate to high intensities on the bike, in the pool, or on the trails, you might be able to go longer. with less reliance on carb refueling.
So the theory is sound, but is the technology reliable? Peer-reviewed research indicates that Lumen’s miniaturized version of the medical-grade metabolic map technology you’d typically find in a physiology lab is as accurate as the gold standard for measuring respiratory exchange rate (RER ).
What our founding tester
Taking the Lumen test at least once a day unlocked my daily nutrition plan and built my personal breath signature. Each test lasted about five minutes, and Lumen recommends doing this first thing in the morning before eating or exercising to avoid skewed results.
Each breath test reveals whether you are burning fat, carbs or both with a color coded wheel – 1 means you are burning mostly fat, 5 means you are burning mostly carbs. After two weeks, I unlocked my Flex Score, my metabolic flexibility index.
Creating the morning habit was easy. It was harder to remember to take measurements during the day – after eating, and before and after workouts. (Note: Apple Watch and Garmin users can set pre- and post-workout reminders.)
I consider myself low carb, but initially I woke up mostly burning carbs and not fat. Following the plan helped me burn morning fat more often and improved my Flex score slightly – although I didn’t see any staggering weight loss or notice a sudden surge of extra energy.
The biggest benefit was learning more about how the body’s diet works. Lumen is a great teacher and forces you to adapt to when and what you feed your machine. I blindly quit workouts before refueling, while cutting back on late-night carb snacks helped improve my sleep quality.
How Lumen can help you
01. The Fast Lane
Lumen suggests fasting about 2-3 hours before bedtime to empty your carb stores and switch to fat burning overnight.
02. Cycling Mastery
Rather than no carbs, nutrition plans recommend low and high carb days related to your metabolism, goals, and food preferences.
03. Keep Coming Home
Occasional high carb days, tied to your results and activity, help maintain your body’s ability to use carbs as a fuel source.
the MH Verdict
If you’re hoping for a quick fix for weight loss, this isn’t it. Even though Lumen bases its advice on what’s really going on with your body, underneath smart technology there’s still a “diet” that involves precisely monitoring your macro intake – which requires discipline, diligence, and a level of food tracking that has become a bit taxing.
But if you’ve never tapped into what, when, and why you eat, the process is an education. The app’s simple explanations guide you through the somewhat complicated science of metabolic health with brilliant bombshells of knowledge.
It comes with hefty subscription fees, and unlocking its greatest health benefits is definitely a long-term commitment, not a quick fix. But that is perhaps its greatest strength.
£249 for 6 months, then a monthly subscription of £25.
Kieran Alger is a journalist and endurance runner who researches the smartest tools to improve health, training and performance.
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