An Interview with Calorify’s Scientific Advisor, Herman Pontzer
Calorify’s Scientific Advisor, Herman Pontzer, has been studying metabolism for over 20 years. His interests range from how human history shapes our metabolism today to how physical activity is tied to our physical design. He has done extensive field and lab research, traveling to Africa and South American to study the metabolism of hunter-gatherer communities.
Regarded as a leader in the field, Herman is regularly published in top journals, has been written about in Science and the Scientific American, and even published his own book Burn: New Research Blows the Lid Off How We Really Burn Calories, Lose Weight, and Stay Healthy to bring his research to the general public. Now a Professor of Evolutionary Anthropology at Duke University, he has served as an incredible guide for us as we now strive to bring metabolic testing to everyone. In this interview, Herman answers questions about how he got connected to Calorify, the doubly labeled water (DLW) technique, what gets him excited about the work, and more!
Q: Why did you join Calorify?
A: I've been studying energy expenditure in people around the world for my entire career. I'm continually impressed by the insights we gain from these measures, understanding how lifestyle, body weight, age, and other factors can affect the calories you burn each day. But until Calorify, there hasn't been any way for people to experience these insights themselves. I'm excited to be part of the first company to offer these insights to the broader public. Also, the methods Calorify uses are the same as we use in research, so I feel that I have expertise and insights that contribute to Calorify's mission.
Q: Tell us a bit more about your academic journey. How did you wind up here?
A: I'm trained as an Evolutionary Anthropologist. I want to understand how the body works and how it evolved. Energy expenditure always piqued my interest as a great way to understand the entire body and to bridge between anatomy, physiology, and evolution. After all, as I like to say, from a biological point of view, life is just a game of turning energy into offspring.
I spent my early career focused on energy expenditure during exercise, developing and testing new biomechanical models that link the energy cost of walking and running to the anatomy of our legs. I started working with DLW a bit later, as I wanted to broaden the sorts of questions I was asking and understand how the body burns calories throughout the entire day. That work, particularly the exciting results from working with the Hadza, sparked a career focused on bringing doubly labeled water (DLW) to populations and settings where it hasn't traditionally been used. Calorify is a big part of that, in my mind, bringing DLW to the broader public.
Q: Doubly labeled water is the gold standard technique for measuring real world calories. What is this method and what are some of the main things we’ve learned from its use?
A: Doubly labeled water, or DLW, uses two safe forms of water to track the calories your body burns each day. Most people know that water is H2O, made from hydrogen and oxygen atoms. What a lot of people don't know (or forgot from high school chemistry) is that atoms come in multiple forms, called isotopes. Some isotopes are unstable and therefore unsafe, but many are completely stable and safe, and used by our bodies all the time. DLW uses water with a safe form of hydrogen (called deuterium) and a safe form of oxygen (oxygen-18). Those isotopes act like tracers, allowing Calorify to calculate how much carbon dioxide (CO2) your body produces each day. CO2 is the waste product from burning calories - you can't make CO2 without burning calories, and you can't burn calories without making CO2. By measuring CO2, the DLW method that Calorify uses provides a precise, accurate, and reliable measurement of the calories you burn each day.
Q: Doubly labeled water has been widely accepted in research for decades yet has not been available to the public until now. How can Calorify change the world?
A: Knowledge is power. We often talk about our metabolism like an unknowable black box that makes us fat or lets us down. None of that is true. Calorify gives people the information they need about their bodies to manage their nutrition, exercise, weight, and a lot more.
Q: Could you tell us a bit more about your research with doubly labeled water? What are some of your most provocative findings?
Photo courtesy of Herman Pontzer
A: Some of the coolest research I've had the opportunity to do is working with the Hadza hunter-gatherer community in northern Tanzania. Many Hadza families still follow a hunting and gathering way of life - no farming, vehicles, guns, electricity. Men hunt wild game with bow and arrow, or collect wild honey. Women gather berries, tubers, and other plant foods. It's a physically demanding way to live! Hadza men and women get more physical activity in a day than the typical American gets in a week.
We wanted to understand how this active lifestyle affects the calories burned each day. To our surprise, we found that Hadza men and women don't burn any more calories than Americans do each day. Being more active doesn't necessarily lead to burning more calories!
We've since seen this in other studies and other populations as well, including studies where people enroll in new exercise studies. The total calories burned each day is typically less than you'd expect from differences in activity. Sometimes, like the Hadza, there's no difference at all between active and sedentary people. The body is dynamic and complex, and it can rebudget the way it spends its calories in ways that are hard to predict.
That's why online calorie counters and smartwatches are so bad at predicting the calories you burn each day. They are built with the assumption that the body is simple, that your metabolism is like a car engine. Neither is true. Your body is complex and dynamic, and your metabolism is too. That's why DLW is such an important and useful tool. It doesn't rely on simple (and incorrect) assumptions about the body.
Q: At Calorify, we work with a lot of top athletes and teams. What are the ways in which metabolism drives athletic performance? What are some fundamental limits to metabolism and their implications for performance?
A: We are finding two "metabolic ceilings" that seem to limit what the body can sustain. First, there seems to be a hard limit on the number of calories you can burn each day. The limit is higher for shorter events (you can burn more per day in a 1-day ultramarathon than in the 4-week Tour de France, for example). We don't have any credible measurements of athletes pushing beyond that ceiling, and it seems the body likely begins to break down if you try. Second, there seems to be a limit on the number of calories your body can absorb. This sets the long-term limit on how many calories you can burn as well, since you can't stay in negative energy balance (eating less than you burn) forever.
Together, the emerging science in this area suggests that athletes need to manage their training and competition schedules very carefully. A workload that's sustainable for a few days or even a few weeks might lead to problems long term. Measures of daily energy expenditure can help athletes manage their training.
Q: We’ve noticed a lot of confusion about metabolism and weight (loss). If you’re trying to lose weight, what should you know about metabolism?
A: At the end of the day, weight loss really is about "calories in, calories out." But that doesn't mean it's easy! Your body can adjust the way it burns calories, making it virtually impossible to accurately assess the calories you burn each day. It's also really hard to track the calories you eat (and food labels don't always help!). The key to sustainable weight loss is finding a diet and lifestyle that get you eating fewer calories than you burn without feeling miserable. Lots of diets and approaches can work!
Q: Your first book, Burn: New Research Blows the Lid Off How We Really Burn Calories, Lose Weight, and Stay Healthy, is an exceptional piece of science communication that shares the new science of metabolism being driven by doubly labeled water. What’s your next book about and what does it mean for Calorify customers?
A: The book I'm working on now explores how our bodies work, and how each of us is unique. Our bodies have the same parts, organs and hormones that work the same way, even genes that are very similar, and yet no two bodies are identical - not even identical twins. How do we make sense of our differences as well as our similarities? How do we understand our bodies - ourselves - as well as the people around us? The book will cover a lot of fun physiology as well as deeper questions about our daily lives and experiences.
People who use Calorify will find a lot in common with the book, I think. The Calorify motto, "No Body Burns the Same" speaks to our individuality and the importance of understanding the ways your body is unique.
