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By Matthew Rees

Food and Health Fact #194:

Measuring your metabolism and calculating your body's gas mileage

Find my recent 90-minute interview with PLANTSTRONG founder Rip Esselstyn here I post on Twitter semi-regularly. Find me at @foodhealthfacts The full catalog of my previous posts, articles, and commentaries can be found on the Food and Health Facts website

It’s one thing to count the calories you consume. But that’s only half the equation when trying to determine how much to eat. What about the calories you burn? There’s traditionally been no precise way to measure this.

But a California-based company says it’s now possible. Calorify claims to be the first lab to commercialize a precise method of measuring metabolic rates, adding that while the science has existed for 70 years, testing has only been available to people participating in academic research (fewer than 15,000 people). “We’re excited to democratize what we believe is one of the most important data points about your body,” reads the Calorify website.

I recently interviewed the company’s cofounder and CEO, Hari Mix, who was a professor at Santa Clara University before leaving to focus on Calorify.

What’s the problem Calorify is trying to solve?
One of the most fundamental numbers about your body is your gas mileage, the rate at which you burn fuel (in calories per day). Each of our 37 trillion cells takes energy to run, and for the first time ever, Calorify lets everyday customers learn this vital aspect of themselves.

Knowing your personal “calories out” is particularly useful if you have a weight or body fat goal (e.g. losing fat or building muscle) because it allows you to adjust your caloric intake to set yourself up for success. Another common use case for Calorify customers are athletes who are looking to meet their nutritional needs demanded by their training.

Once people know their “gas mileage,” what do they do with it? And does Calorify make specific recommendations about how much to eat? And what to eat?
Customers do a variety of things with this valuable data once they obtain it. Customers have a particular weight or body composition goal learn exactly how much to eat to reach their goal. Calorify consults with each customer after they test to come up with a custom body weight, body composition or training plan. Calorify is agnostic to any approach you may want to take, so aside from recommending specific calorie targets and other basics like protein intake, Calorify lets you decide how to go about reaching your goal. Want to switch to vegan or keto? Great! But now you can measure how your metabolism responds.

Precisely how does Calorify help people count calories?Calorify measures your metabolic rate using the doubly labeled water method. By taking a sip of Calorify’s water (literally H2O with rare forms of hydrogen and oxygen) and collecting urine samples, Calorify accurately measures how much CO2 you respire, and therefore calories you burn.

Calorify starts by measuring how many calories you burn. If customers weigh in while testing, they also learn how many calories they’re eating more accurately than they can count on their own.

How can this be used in everyday life? Or when trying to lose weight?An example of personalized calorie targets: Say your goal is to lose weight. What you mean is you’d like to lose fat. Hardly anyone wants to lose muscle but not fat. Weight loss requires a calorie deficit, but the specific deficit will determine the amount of fat vs muscle that you lose. For maximum safe fat loss, Calorify recommends a 25% deficit (relative to your metabolism that only Calorify can measure). This is a deep enough deficit that you lose fat efficiently, but not so deep that you lose excess muscle or yoyo in and out of your goal weight because you picked an unsustainably aggressive calorie target.

What’s distinctive about Calorify?
Calorify offers the public, for the first time ever, a lens into their metabolism. How much energy you bring into your body and how you spend that energy paycheck are fundamental aspects of what makes you human. Calorify’s mission is to advance access and understanding of the human energy budget. This means both empowering individuals to understand and improve their bodies as well as to further the scientific understanding of metabolism and drive solutions to metabolic diseases.

Why can’t people just use fitness trackers?
Fitness trackers may be useful in tracking, well, exercise. But they’re not at all useful in tracking overall daily calories. Research has shown activity trackers and smartwatches to be no more than 55% accurate compared to Calorify (~97% accurate). This means your watch can be off by thousands of calories per day.

Is there a profile of a typical Calorify user/customer?
Calorify’s customers come from all walks of life, but at least 20% are elite or professional athletes including NBA players, Olympic champions, professional marathoners, and more. Other customers come to Calorify looking to address a particular problem with their body, be it a muscular disease, thyroid issue, or diabetes. Many are motivated to lose fat, and some are simply interested in learning more about themselves.

Where did the idea for the company come from? And when was it founded?
I first learned of the science behind Calorify as a professor at Santa Clara University. I had the academic expertise to make these measurements but had not yet done them in my lab. I became even more interested in metabolism when training to climb the 8th highest mountain in the world without supplemental oxygen (I summited!).

Before and during the expedition, I worked with Dr. Herman Pontzer (a professor at Duke University) to test his metabolism at extreme altitude. I not only learned more about his caloric needs but also developed a strategy to preserve muscle during this extreme activity. A few months later, I connected with my longtime friend and Stanford track teammate John McGuire. We realized the opportunity was too important to pass up . . . it simply meant too much to the world.

In December 2021, we founded Calorify and soon brought on Dr. Pontzer as Scientific Advisor.

Dr. Pontzer is the author of the critically-acclaimed Burn: New Research Blows the Lid Off How We Really Burn Calories, Lose Weight, and Stay Healthy. Does Calorify build on his work? If so, which elements of his work?
Great question! I think there are a couple areas where we’ve made contributions. One is in the method itself. We’ve learned a lot about the process of analyzing these samples and have made some major improvements in cost and efficiency. We hope these will benefit the research community in the future.

The main area where we’re advancing Dr. Pontzer’s mission is in studying elite athletes working at the extremes of metabolism. We’ve made some interesting observations with the world’s top athletes that have implications for what’s possible to achieve as a human.

One of the most interesting areas where we’re working is on measures of how much you’re training and if you’re overtraining. We can calculate how much metabolic work you’re doing and if that work is sustainable. We can also calculate how much energy availability you have . . . the non-exercise calories you have left to do the essential functions you need to be healthy.

Why hasn’t something like this even been available before?

The Calorify lab makes extremely precise measurements of stable oxygen and hydrogen isotopes. The traditional way of making these measurements used what’s called mass spectrometry. This requires extremely expensive and finnicky instrumentation and skilled users. Calorify uses a newer technology, a form of laser absorption spectroscopy (off-axis integrated cavity output spectroscopy for the nerds) that makes the same measurements faster and in a more simple, stable manner. In addition, Calorify has streamlined the procedure to make it more efficient both in terms of cost and time.

Is it correct that about 60-65 percent of all the calories humans burn everyday stems from just the basics of staying alive, such as our heart pumping?
Yes. This is called basal metabolic rate – the energy required to simply stay alive at complete rest (breathing, heart pumping, maintaining your body temperature, running your brain). A person with average activity level (e.g. exercising moderately several times per week) will have a basal metabolic rate that is about 60-65% of their total calorie burn, referred to as total energy expenditure.

How do humans burn the rest of their calories?
A lot of ways! Stress and anxiety can increase how many calories you burn. Your immune system burns calories. Fidgeting burns calories. Digesting food burns calories. And then there’s all of the activity, both purposeful exercise as well as non-exercise like grocery shopping, walking up the stairs, picking up a child, etc.

Herman Pontzer has written that, “For all the talk about metabolism in the exercise and dieting worlds, you would think the science was settled. In reality, we've been embarrassingly short on hard data about the calories we burn each day and how we evolved to obtain them.” Can you elaborate on this?
This is correct. The main reason is that measuring metabolism has been extremely hard and expensive. Though the technology to do so has existed for decades, only about 1 person per day has been tested globally! Calorify has made great strides by offering this test to the public for the first time and providing results rapidly (2 days or less).

Recognizing that everyone is different, can you make any general statement about the relative importance of diet vs. exercise in losing weight?

For most people, it’s easiest to change your weight in the kitchen vs the weightroom or treadmill. Exercise simply doesn’t burn as many calories as people think. Simultaneously, people underestimate the amount they eat, typically by about 30%.