The feasibility and acceptability of morning versus evening exercise for overweight and obese adults: A randomized controlled trial

Abstract

Background: The time of day that people exercise could have an influence on the efficacy of exercise for weight loss, via differences in adherence and/or physiological adaptations. However, there is currently no evidence to support an optimal time of day for exercise to maximise efficacy.

Purpose: To examine the feasibility and acceptability of prescribed morning and evening exercise.

Methods: Twenty inactive, overweight adults aged 18-60 years were recruited for a 12-week intervention and randomized to one of three groups using a 2:2:1 random allocation ratio: i) morning exercise (AM; n = 9); ii) evening exercise (PM; n = 7); or iii) waitlist control (CON; n = 4). Exercise groups were prescribed self-paced walking or running on a treadmill to achieve a weekly total of 250 min. Feasibility and acceptability data were collected, and physiological and behavioural outcomes associated with energy balance were measured at baseline, mid- and post-intervention.

Results: Attrition was low (n = 2 dropped out), with high measurement completion rates (>80%). The intervention groups had high adherence rates to exercise sessions (94% and 87% for the AM and PM groups, respectively). No adverse events resulting from the intervention were reported. Both intervention groups displayed improvements to their cardiometabolic risk profile; cardiorespiratory fitness improved by 5.2 ± 4.7, and 4.6 ± 4.5 mL kg^-1.min^-1 and body fat percentage reduced by 1.2 ± 1.4, and -0.6 ± 1.2% for AM and PM groups, respectively.

Conclusion: This feasibility study provides evidence that morning and evening exercise interventions are feasible, and also provides justification for a large-scale randomized controlled trial.

Trial registration: This trial is registered with the Australian New Zealand Clinical Trials Registry (ACTRN12616000457448p, 7/4/2016).

Keywords: 3-FU, 3-month follow-up; 6-FU, 6-month follow-up; AM, morning exercise; BL, baseline; BMI, body mass index; CON, control; DXA, dual x-ray absorptiometry; Energy balance; Exercise; Feasibility; LFPQ, Leeds food preference questionnaire; MARCA, Multimedia activity recall for children and adults; MEQ, morningness-eveningness questionnaire; MVPA, moderate-vigorous physical activity; PAL, physical activity level; PM, evening exercise; PSQI, Pittsburgh sleep quality index; RMR, resting metabolic rate; RPE, ratings of perceived exertion; Randomized controlled trial; TFEQ, three-factor eating questionnaire; Time of day; VAS, visual analogue scale; VO2peak, peak oxygen uptake.

Fig. 1

Overview of protocol by outcome measure. BL = baseline, MID = mid-intervention, POST = post-intervention.

Fig. 2

CONSORT flow diagram of participant progression through the study. AM = morning exercise group, CON = control group, PM = evening exercise group.