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Exciting discovery about exercise effects on fat burning

[Aug. 11, 2023: Staff Writer, The Brighter Side of News]

Advertised on numerous workout devices, this concept offers an ideal heart rate bracket for eliminating extra weight. (CREDIT: Creative Commons)

In the fitness world, the appeal of the "fat-burning zone" has long been accepted without question. Advertised on numerous workout devices, this concept offers an ideal heart rate bracket for eliminating extra weight. However, innovative studies from the Icahn School of Medicine at Mount Sinai have sparked a debate, hinting that those aiming for fat reduction may need to reconsider these standardized recommendations.

Published in Nutrition, Metabolism and Cardiovascular Disease, this study emphasizes the potential misalignment between commercial “fat-burning zone” indicators and an individual's optimal fat loss heart rate.


Using an advanced machine learning-based modeling approach, the research not only offers a more scientific perspective on exercise intensities for weight loss but could also herald a new era of personalized exercise prescriptions.

“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,” explained lead author Hannah Kittrell, MS, RD, CDN. She's not just a PhD candidate at Icahn Mount Sinai's Augmented Intelligence in Medicine and Science laboratory, but also the Director of the Mount Sinai Physiolab.


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Kittrell continues, “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.”

The term FATmax is a relevant one in this context. It denotes the exercise intensity and the corresponding heart rate when our bodies burn fat at its maximum rate during aerobic exercise. Since fat is a significant energy source at this intensity, understanding and achieving one's personal FATmax could be pivotal for those dedicated to optimized fat loss during their workouts.


The Real Numbers: Measured vs. Predicted Heart Rates

The study took a closer look at this by comparing the heart rate at FATmax, as observed during a clinical exercise test, to the heart rate predicted by the often-recommended “fat-burning zone” guidelines. Their findings were eye-opening.

The study uncovered individual variations in fat burning during exercise. Graphs of two people's fat burning curves highlight differences in fat burning rates at varying exercise intensities and demonstrate that fatMAX falls outside the predicted “fat burning zone.” These variations underscore the need for personalized exercise plans. (CREDIT: Hannah Kittrell, Mount Sinai Physiolab and AIMS Lab at Icahn Mount Sinai)

Analyzing a sample of 26 individuals, there was a glaring discrepancy between the measured and predicted heart rates. The mean difference stood at a staggering 23 beats per minute. This indicates that the one-size-fits-all “fat-burning zone” might be leading many astray in their fitness journeys.


The Future: Personalized, Data-Driven Exercise Prescriptions

With these insights in hand, the researchers are gearing up for the next phase. They intend to investigate whether tailor-made exercise prescriptions can potentially enhance weight and fat loss and better metabolic health markers—key indicators for health risks such as type 2 diabetes, obesity, and heart disease.

Senior author Girish Nadkarni, MD, MPH

Senior author Girish Nadkarni, MD, MPH, emphasized the significance of this shift. “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,” he stated. As the Irene and Dr. Arthur M. Fishberg Professor of Medicine at Icahn Mount Sinai and the Director of The Charles Bronfman Institute of Personalized Medicine, Nadkarni's words carry weight.


“It also emphasizes the role that data-driven approaches can have toward precision exercise,” Nadkarni added, highlighting the transformative potential of integrating modern data analytics into fitness regimes.

The FatMax test lasts about 20-45 min, depending mostly on how trained the athlete is. The test starts at a low intensity (equivalent to walking) and every 3 min the intensity is increased (power on a bike or speed on a treadmill). During the test, expired gases are collected and/or measured from the athlete. This is used to calculate fat burning as well as carbohydrate burning. (CREDIT: Mysportscience)

Titled “Discrepancy between predicted and measured exercise intensity for eliciting the maximal rate of lipid oxidation”, this paper is bound to change our understanding of fat loss and exercise. With a future of personalized fitness on the horizon, it’s time to rethink the traditional “fat-burning zone” and look towards a more data-driven, individualized approach to health and fitness.


Through the Mount Sinai Innovation Partners (MSIP), the Health System facilitates the real-world application and commercialization of medical breakthroughs made at Mount Sinai. Additionally, MSIP develops research partnerships with industry leaders such as Merck & Co., AstraZeneca, Novo Nordisk, and others.

For more science and technology stories check out our New Discoveries section at The Brighter Side of News.


Note: Materials provided above by The Brighter Side of News. Content may be edited for style and length.


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