Biological and psychological mediators of the relationships between fat mass, fat-free mass and energy intake

Int J Obes (Lond). 2019 Feb;43(2):233-242. doi: 10.1038/s41366-018-0059-4. Epub 2018 Mar 13.


Background: While recent studies in humans indicate that fat-free mass (FFM) is closely associated with energy intake (EI) when in energy balance, associations between fat mass (FM) and EI are inconsistent.

Objectives: The present study used a cross-sectional design to examine the indirect and direct effects of FFM, FM and resting metabolic rate (RMR) on EI in individuals at or close to energy balance.

Methods: Data for 242 individuals (114 males; 128 females; BMI = 25.7 ± 4.9 kg/m2) were collated from the non-intervention baseline conditions of five studies employing common measures of body composition (air-displacement plethysmography), RMR (indirect calorimetry) and psychometric measures of eating behaviours (Dutch Eating Behaviour Questionnaire). Daily EI (weighed dietary records) and energy expenditure (flex heart rate) were measured for 6-7 days. Sub-analyses were conducted in 71 individuals who had additional measures of body composition (dual-energy X-ray absorptiometry) and fasting glucose, insulin and leptin.

Results: After adjusting for age, sex and study, linear regression and mediation analyses indicated that the effect of FFM on EI was mediated by RMR (P < 0.05). FM also independently predicted EI, with path analysis indicating a positive indirect association (mediated by RMR; P < 0.05), and a stronger direct negative association (P < 0.05). Leptin, insulin and insulin resistance failed to predict EI, but cognitive restraint was a determinant of EI and partially mediated the association between FM and EI (P < 0.05).

Conclusions: While the association between FFM and EI was mediated by RMR, FM influenced EI via two separate and opposing pathways; an indirect 'excitatory' effect (again, mediated by RMR), and a stronger direct 'inhibitory' effect. Psychological factors such as cognitive restraint remain robust predictors of EI when considered alongside physiological determinants of EI, and indeed, have the potential to play a mediating role in the overall expression of EI.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adipose Tissue / physiology*
  • Adult
  • Basal Metabolism / physiology
  • Body Composition / physiology*
  • Cross-Sectional Studies
  • Diet
  • Energy Intake / physiology*
  • Feeding Behavior / physiology
  • Female
  • Humans
  • Male
  • Middle Aged