Influence of fat-free mass and resting metabolic rate on increased food reinforcement after exercise training

Authors: PANKEY, CHRISTOPHER - West Virginia School Of Osteopathic Medicine; FLACK, KYLE - University Of Kentucky; UFHOLZ, KELSEY - Case Western Reserve University (CWRU); JOHNSON, LUANN - University Of North Dakota; Roemmich, James

Submitted to: Sport Sciences for Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2021
Publication Date: 1/1/2022
Citation: Pankey, C., Flack, K., Ufholz, K., Johnson, L., Roemmich, J.N. 2022. Influence of fat-free mass and resting metabolic rate on increased food reinforcement after exercise training. Sport Sciences for Health. 18:923–931. https://doi.org/10.1007/s11332-021-00876-y.
DOI: https://doi.org/10.1007/s11332-021-00876-y

Interpretive Summary: The drive to eat has largely been thought to be a function of the brain receiving signals from the stomach, intestines, and fat cells. However, the lean tissue in our body is the primary user of energy stores so our lean tissue could also play an important role in the motivational drive for food intake (RRVfood). Chronic exercise-induced weight loss can reduce energy stored as fat mass (FM), can increase lean tissue (FFM), and alter the rate of energy expended at rest (i.e., resting metabolic rate, RMR) and provides an opportunity to test whether the change (D) in FM (DFM), DFFM, DUsual EI, or DRMR are associated with DRRVfood. After 12 weeks of aerobic exercise training the amount of FFM the people had correlated with how many calories people ate (rs'='0.41, p'<'0.05), the motivation to eat (RRVfood), and the rate at which they expended calories at rest (RMR). Decreases in RMR were correlated with an increase in the motivation to eat. We concluded that reductions in RMR with weight loss may increase food reinforcement as means of restoring FFM and RMR to pre-weight loss amounts. Limiting reductions in RMR during weight loss may benefit weight maintenance by restricting increases in food reinforcement after weight loss.

Technical Abstract: Models of appetite control have been largely based on negative feedback from gut and adipose signaling to central appetite centers. However, contemporary models posit that fat-free mass (FFM) or the energy demand of FFM [i.e., resting metabolic rate (RMR)] may play a primary role in the motivational drive for food intake (i.e., food reinforcement). The relative reinforcing value of food (RRVfood) is associated with energy intake (EI) and increases with an acute energy deficit. Chronic exercise-induced energy deficits lead to alterations in fat mass (FM), FFM, and RMR and provide an opportunity to test whether change in (D) FM, DFFM, DUsual EI, or DRMR are associated with DRRVfood. Methods Participants (n'='29, BMI'='25–35 kg/m2) engaged in aerobic exercise expending 300 or 600 kcal, 5 days/weeks for 12 weeks. The reinforcing value of food (PMaxfood) was measured via a computer-based operant responding task and RRVfood was calculated as the reinforcing value of food relative to non-eating sedentary behaviors. RMR was determined by indirect calorimetry and body composition by DXA. Results Post-training FFM correlated with usual post-training EI (rs'='0.41, p'<'0.05), PMaxfood (rs=0.52, p'<'0.01), and RMR (rs'='0.85, p'<'0.0001). DRMR negatively correlated with DPMaxfood (rs'='- 0.38, p'<'0.05) and with DRRVfood (rs'='- 0.37, p'<'0.05). DPMaxfood and DRRVfood were not associated with DFFM (p'='0.71, p'='0.57, respectively). Conclusions Reductions in RMR with weight loss may increase food reinforcement as means of restoring FFM and RMR to pre-weight loss amounts. Limiting reductions in RMR during weight loss may benefit weight maintenance by restricting increases in food reinforcement after weight loss.