Dose-Response of Myofibrillar Protein Synthesis To Ingested Whey Protein During Energy Restriction in Overweight Postmenopausal Women: A Randomized, Controlled Trial

Larsen, Mads S.; Witard, Oliver C.; Holm, Lars; Scaife, Paula; Hansen, Rikke; Smith, Kenneth; Tipton, Kevin D.; Mose, Maike; Bengtsen, Mads B.; Lauritsen, Katrine M.; Mikkelsen, Ulla R.; Hansen, Mette

Abstract

Background
Diet-induced weight loss is associated with a decline in lean body mass, as mediated by an impaired response of muscle protein synthesis (MPS). The dose-response of MPS to ingested protein, with or without resistance exercise, is well characterized during energy balance but limited data exist under conditions of energy restriction in clinical populations.

Objective
To determine the dose-response of MPS to ingested whey protein following short-term diet-induced energy restriction in overweight, postmenopausal, women at rest and postexercise.

Design
Forty middle-aged (58.6±0.4 y), overweight (BMI: 28.6±0.4), postmenopausal women were randomly assigned to 1 of 4 groups: Three groups underwent 5 d of energy restriction (∼800 kcal/d). On day 6, participants performed a unilateral leg resistance exercise bout before ingesting either a bolus of 15g (ERW15, n = 10), 35g (ERW35, n = 10) or 60g (ERW60, n = 10) of whey protein. The fourth group (n = 10) ingested a 35g whey protein bolus after 5 d of an energy balanced diet (EBW35, n = 10). Myofibrillar fractional synthetic rate (FSR) was calculated under basal, fed (FED) and postexercise (FED-EX) conditions by combining an L-[ring-13C6] phenylalanine tracer infusion with the collection of bilateral muscle biopsies.

Results
Myofibrillar FSR was greater in ERW35 (0.043±0.003%/h, P = 0.013) and ERW60 (0.042±0.003%/h, P = 0.026) than ERW15 (0.032 ± 0.003%/h), with no differences between ERW35 and ERW60 (P = 1.000). Myofibrillar FSR was greater in FED (0.044 ± 0.003%/h, P < 0.001) and FED-EX (0.048 ± 0.003%/h, P < 0.001) than BASAL (0.027 ± 0.003%/h), but no differences were detected between FED and FED-EX (P = 0.732) conditions. No differences in myofibrillar FSR were observed between EBW35 (0.042 ± 0.003%/h) and ERW35 (0.043 ± 0.003%/h, P = 0.744).

Conclusion
A 35 g dose of whey protein, ingested with or without resistance exercise, is sufficient to stimulate a maximal acute response of MPS following short-term energy restriction in overweight, postmenopausal women, and thus may provide a per serving protein recommendation to mitigate muscle loss during a weight loss program.

Trial registry
clinicaltrials.gov (ID: NCT03326284).

Citation

Larsen, M. S., Witard, O. C., Holm, L., Scaife, P., Hansen, R., Smith, K., …Hansen, M. (2023). Dose-Response of Myofibrillar Protein Synthesis To Ingested Whey Protein During Energy Restriction in Overweight Postmenopausal Women: A Randomized, Controlled Trial. The Journal of Nutrition, 153(11), 3173-3184. https://doi.org/10.1016/j.tjnut.2023.08.011

• Journal Article Type: Article
• Acceptance Date: Aug 10, 2023
• Online Publication Date: Aug 19, 2023
• Publication Date: 2023-11
• Deposit Date: Nov 23, 2023
• Publicly Available Date: Nov 23, 2023
• Journal: The Journal of Nutrition
• Print ISSN: 0022-3166
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 153
• Issue: 11
• Pages: 3173-3184
• DOI: https://doi.org/10.1016/j.tjnut.2023.08.011
• Public URL: https://durham-repository.worktribe.com/output/1932443