Effects of Time-Restricted Eating on Aerobic Capacity, Body Composition and Markers of Metabolic Health in Healthy Men

Abstract

We sought to explore the effects of four weeks of time-restricted eating (TRE) vs. regular diet on aerobic capacity, body composition and metabolic health in trained young males (15 participants, aged 24.4±3.3 years). We defined two primary hypotheses: (1) that the magnitude of FM loss would be greater with TRE than with a regular dietary pattern and (2) that both dietary approaches would result in comparable improvements in FFM, skeletal muscle mass and aerobic capacity. The order of dieting was randomized and counterbalanced, and participants served as their own controls. TRE involved an 8-h eating window and non-TRE involved a regular meal pattern. Participants completed graded exercise tests and body composition scans at baseline and post-intervention. Fasted blood samples were analysed for glucose and lipids. The participants followed a structured training routine during each dietary intervention (3 heavy outdoor runs x 10 km/week + 3 severe running bouts x 1000 m). The participants’ body mass post-TRE was lower than post-regular diet (p=0.046). Neither condition elicited changes in fat mass nor fat-free mass between time points. Significant improvements were obtained with both conditions for the first ventilatory threshold, maximum oxygen uptake (VO2max) and velocity at VO2max (p<0.05). Based on our findings, four-weeks of TRE can be used in combination with endurance running to elicit body mass reductions in trained males. Yet, when compared with regular diet, TRE does not offer any benefit for improving submaximal or peak exercise capacity in well-trained males.

Note:
Funding Information: This work was partly supported by the Fundação para a Ciência e Tecnologia, under Grant UIDB/00447/2020 to CIPER—Centro Interdisciplinar para o Estudo da Performance Humana (unit 447) and by Universidade de Lisboa (grant attributed to J.M.C.-n C00246e).

Conflict of Interests: The authors declare that they have no competing interest.

Ethical Approval: Participants received verbal information about the risks, requirements, and procedures of the study, and provided written informed consent prior to study entry, which was approved by the faculty ethics committee (CEFMH Nº12/2018) and conducted in accordance with the Declaration of Helsinki.

Keywords: intermittent fasting, nutrition, diet, endurance, Training, running