Fat Burning During Exercise Varies Between People

Fat Burning Zones on commercial exercise machines may not be aligning with the best heart rate for the individual using the equipment as the best heart rate for burning fat differs between each person. But, clinical exercise testing may be a useful tool to help people achieve the intended fat loss goal. This testing is a diagnostic procedure that measures an individual’s physiological response to exercise and helps determine their optimal fat-burning zone. The term FATmax is sometimes used to represent when exercise intensity and associated heart rate are at their peak to achieve maximum fat burning.

"People with a goal of weight or fat loss may be interested in exercising at the intensity which allows for the maximal rate of fat burning. Most commercial exercise machines offer a 'fat-burning zone' option, depending upon age, sex, and heart rate," says lead author Hannah Kittrell, MS, RD, CDN, a Ph.D. candidate at Icahn Mount Sinai in the Augmented Intelligence in Medicine and Science laboratory, and is also Director of the Mount Sinai Physiolab, a clinical body composition and exercise physiology laboratory at Mount Sinai Morningside. "However, the typically recommended fat-burning zone has not been validated, thus individuals may be exercising at intensities that are not aligned with their personalized weight loss goals."

For this study the researchers compared heart rate at the FATmax, as measured during a clinical exercise test, to predict heart rate at percentages of maximum effort with the typically recommended fat-burning zone. The researchers found that there was poor alignment between measured and predicted heart rates within a sample of 26 individuals, revealing a mean difference of 23 beats per minute between the measures. These findings suggest that the general recommendations which are typically found on commercial exercise machines for fat-burning zones may not be providing accurate guidance. 

Looking forward, the researchers hope to investigate whether those who receive a more personalized exercise prescription will experience more weight/fat loss as well as improvements in metabolic markers that identify health risks such as heart disease and type 2 diabetes. 

"We hope that this work will inspire more individuals and trainers to utilize clinical exercise testing to prescribe personalized exercise routines tailored to fat loss. It also emphasizes the role that data-driven approaches can have toward precision exercise," says senior author Girish Nadkarni, MD, MPH, Irene and Dr. Arthur M. Fishberg Professor of Medicine at Icahn Mount Sinai, Director of The Charles Bronfman Institute of Personalized Medicine, and System Chief, Division of Data-Driven and Digital Medicine, Department of Medicine.