The best heart rate for burning fat differs hugely between individuals and often does not align with the suggested “fat burning zone” on commercial gym equipment and exercise machines.

That is the headline finding of a study by Icahn School of Medicine (ISM) at Mount Sinai, which researched exercise intensity and associated heart rate at which the body reaches its highest fat-burning rate during aerobic exercise.

It found that the "sweet spot" for optimising fat loss during workouts – often referred to as FATmax – is highly individual.

Instead, the researchers said, clinical exercise testing – a diagnostic procedure to measure a person’s physiological response to exercise – may be a more useful tool to help individuals achieve intended fat loss goals.

The study's lead author, Hannah Kittrell, a PhD candidate at ISM, said: “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.

“However, the typically recommended fat-burning zone has not been validated, thus individuals may be exercising at intensities that are not aligned with their personalised weight loss goals.”

As part of the study, the researchers compared heart rate at FATmax, as measured during a clinical exercise test, to predicted heart rate at percentages of maximal effort within the typically recommended “fat-burning zone".

In a sample of 26 individuals, the researchers found that there was poor agreement between measured and predicted heart rate, with a mean difference of 23 beats per minute between the two measures.

This suggests that general recommendations for a “fat-burning zone” may not provide accurate guidance.

The study's senior author, Girish Nadkarni, said: “We hope that this work will inspire more individuals and trainers to utilise clinical exercise testing to prescribe personalised exercise routines tailored to fat loss. It also emphasizes the role that data-driven approaches can have toward precision exercise."

Next, the researchers plan to study whether individuals who receive a more personalised exercise prescription demonstrate more weight and fat loss, as well as improvement of metabolic health markers that identify health risks like type 2 diabetes, obesity, and heart disease. HCM will report when these findings become available.

• To read the full research paper, titled Discrepancy between predicted and measured exercise intensity for eliciting the maximal rate of lipid oxidation, click here.