MCLA Biology Professor Researches Limit of Calorie Burning with Ultra-Endurance Athletes

Is there a limit to how many calories a person can burn? Dr. Andrew Best, MCLA Assistant Professor of Biology, is currently researching this with ultra-endurance athletes.

Dr. Best is working with Dr. Herman Pontzer and Pontzer Lab from Duke University to study the limits of sustained energy expenditure and the physical capacity for endurance limited by energy. Dr. Best is a biological anthropologist who asks evolutionary questions about human physiology, or, the role of sweating in human evolution, metabolism, energetic limits, and more.

This summer, Dr. Best and Dr. Pontzer are studying a small sample size of 12 ultra-endurance athletes of various ages – as young as 20 and as old as 50 – to understand how many total calories one person can burn.



“It’s a natural experiment where they dedicate their life to burning calories,” Best said. “There’s a
lot of training and multiple competitions. We know that these people are burning a huge number
of calories, and if anyone is going to break our prediction, then it’s them.”

To track data from the sample size, Best uses the doubly-labeled water method to measure totalenergy expenditure (TEE) in ultra-endurance athletes during both ultra events and a 10-day baseline period of normal life and training. Together with basal metabolic rate, or BMR (including measurements taken at MCLA via indirect calorimetry), this will allow Best to calculate metabolic scope (TEE/BMR).

Through the doubly-labeled water method, research participants mail a urine sample every other day for 10 days to Duke University to be tested for special isotopes that tell the researchers the total carbon dioxide production that determines the whole metabolic rate.

By using the TEE/BMR formula, Best receives a number to determine a person's metabolic scope. Right now the research shows many variations; age, frequency of training, intensity of training, and how many calories are being burned. Best only has a full year’s worth of data for five out of the 12 participants, and the person with the highest scope (2.6) is not doing a lot of fo training.

“I’m hoping the data we get this summer will show more variations,” he said.

Best started this research two summers ago after meeting an ultrarunner who broke a record for hiking the Long Trail and wanted data for his next journey on the Arizona Trail. That’s when Best teamed up with Pontzer, and it grew from there.

This past year, Best worked with MCLA undergraduate research assistant, Marie Balan, ‘23, to test different models and the accuracy of equipment – both generic and research-grade – with various volunteers.

“What we’re hoping to do is to get a direct measurement of BMR because right now we’re using a formula,” he said.

Best documents his research on his website and social media,, including a past study on the variation in sweat gland density, in which he hopes to build a thermal room in the MCLA Human Performance Lab for continued testing. He was also quoted in Men’s Health Magazine this summer in an article titled “How to Make Sweat Your Superpower.

Above photo taken by Michael Dillon, @pilotfield on Instagram.