Discrepancy between predicted and measured exercise intensity for eliciting the maximal rate of lipid oxidation

Hannah D Kittrell; Fred J DiMenna; Avigdor D Arad; Wonsuk Oh; Ira Hofer; Ryan W Walker; Ruth J F Loos; Jeanine B Albu; Girish N Nadkarni

doi:10.1016/j.numecd.2023.07.014

Discrepancy between predicted and measured exercise intensity for eliciting the maximal rate of lipid oxidation

Nutr Metab Cardiovasc Dis. 2023 Nov;33(11):2189-2198. doi: 10.1016/j.numecd.2023.07.014. Epub 2023 Jul 15.

Authors

Hannah D Kittrell¹, Fred J DiMenna², Avigdor D Arad³, Wonsuk Oh⁴, Ira Hofer⁵, Ryan W Walker⁶, Ruth J F Loos⁷, Jeanine B Albu², Girish N Nadkarni⁸

Affiliations

¹ Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA; The Charles Bronfman Institute of Personalized Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Mount Sinai Clinical Intelligence Center, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Division of Data Driven and Digital Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA. Electronic address: hannah.kittrell@icahn.mssm.edu.
² Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
³ The Integrated Center for Preventive Medicine, Tel Aviv Medical Center, Tel Aviv, Israel.
⁴ Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA; The Charles Bronfman Institute of Personalized Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Mount Sinai Clinical Intelligence Center, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Division of Data Driven and Digital Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
⁵ The Charles Bronfman Institute of Personalized Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Division of Data Driven and Digital Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Department of Anesthesiology, Pain, and Perioperative Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
⁶ Department of Environmental Medicine and Public Health, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
⁷ The Charles Bronfman Institute of Personalized Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA; The Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
⁸ Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA; The Charles Bronfman Institute of Personalized Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Mount Sinai Clinical Intelligence Center, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Division of Data Driven and Digital Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA; Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, NY, USA.

PMID: 37567789
DOI: 10.1016/j.numecd.2023.07.014

Abstract

Background and aims: Ectopic lipid storage is implicated in type 2 diabetes pathogenesis; hence, exercise to deplete stores (i.e., at the intensity that allows for maximal rate of lipid oxidation; MLO) might be optimal for restoring metabolic health. This intensity ("Fat_max") is estimated during incremental exercise ("Fat_max test"). However, in "the field" general recommendations exist regarding a range of percentages of maximal heart rate (HR) to elicit MLO. The degree to which this range is aligned with measured Fat_max has not been investigated. We compared measured HR at Fat_max, with maximal HR percentages within the typically recommended range in a sample of 26 individuals (Female: n = 11, European ancestry: n = 17).

Methods and results: Subjects completed a modified Fat_max test with a 5-min warmup, followed by incremental stages starting at 15 W with work rate increased by 15 W every 5 min until termination criteria were reached. Pulmonary gas exchange was recorded and average values for V˙ o₂ and V˙ co₂ for the final minute of each stage were used to estimate substrate-oxidation rates. We modeled lipid-oxidation kinetics using a sinusoidal model and expressed MLO relative to peak V˙ o₂ and HR. Bland-Altman analysis demonstrated lack of concordance between HR at Fat_max and at 50%, 70%, and 80% of age-predicted maximum with a mean difference of 23 b·min^-1.

Conclusion: Our results indicate that estimated "fat-burning" heart rate zones are inappropriate for prescribing exercise to elicit MLO and we recommend direct individual exercise lipid oxidation measurements to elicit these values.

Keywords: Age-predicted maximum heart rate; Exercise; Insulin resistance; Lipid oxidation; Metabolic health.

Copyright © 2023 The Italian Diabetes Society, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V. All rights reserved.