Resting and total energy expenditures are significantly lower among patients with long chain fatty acid oxidation disorder (LCFAOD), according to a study presented at the 2023 lecture series of the International Network for Fatty Acid Oxidation Research and Management (INFORM) and published in the journal Molecular Genetics and Metabolism

“Our overall conclusion is that subjects with a LCFAOD have lower energy expenditure due to a lower resting metabolic rate,” the researchers wrote. “Additional studies are needed to confirm or refute the lower [resting energy expenditure] and [total energy expenditure] measured in subjects with LCFAODs compared to control data.”

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Energy needs are estimated using formulas derived from normal populations. However, energy expenditures in patients with LCFAOD is not known, the investigators noted.

To find out, a team of researchers led by Melanie B. Gillingham, PhD, RD, an associate professor in Molecular and Medical Genetics at Oregon Health & Science University in Portland, Oregon, measured the resting energy expenditure, total energy expenditure, and body compositions of 31 people with LCFAOD, who were 7 years to 64 years of age. 

They found that the resting energy expenditure that was measured was lower than the resting energy expenditure estimated using various prediction equations. Similarly, the measured total energy expenditure was lower than what was estimated. 

“It is possible that the lower energy expenditure based on prediction formulas from the normal population is due to differences in body composition,” the researchers noted.

Therefore, they compared the body compositions of the patients to that of “normal” data obtained from the 2017–2018 National Health and Nutrition Examination Survey (NHANES). 

They found that fat-free mass and fat mass were similar between people with LCFAOD and the NHANES normal data suggesting no difference in body composition.

The researchers then compared measured resting and total energy expenditures to normal published data from the Dietary Reference Intakes and found that both were significantly lower in patients with LCFAOD compared to normal published energy expenditure data.

“Our results suggest patients with a LCFAOD exhibit a lower [resting energy expenditure] and therefore actually have a slightly lower [total energy expenditure] than estimated,” they concluded. “Current prediction equations may overestimate energy expenditure of patients with a LCFAOD.”

They concluded that the lower resting and total energy expenditures could be the result of lower mitochondrial respiration and energy expenditure or be due to increased anaerobic metabolism.


Gillingham M. Energy expenditure in FAODs. Lecture presented at the International Network for Fatty Acid Oxidation Research and Management (INFORM) 2023 lecture series: June 19, 2023; Virtual. 

DeLany JP, Horgan A, Gregor A, Vockley J, Harding CO, Gillingham MB. Resting and total energy expenditure of patients with long-chain fatty acid oxidation disorders (LC-FAODs). Mol Genet Metab. Published online January 18, 2023. doi:10.1016/j.ymgme.2023.107519