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Morning or Afternoon Exercise: Which Time of Day Provides the Most Benefits?

Mar 16, 2021
 
Editor: David L. Joffe, BSPharm, CDE, FACA

Author: Alexis Dunn, PharmD. Candidate, Florida Agricultural & Mechanical University, College of Pharmacy and Pharmaceutical Sciences

Is there a difference in the effect on glucose control and metabolic health when people exercise in the morning vs. in the afternoon? 

Exercising is essential in managing glucose control because insulin sensitivity and glucose levels improve. Recent studies have shown that the circadian rhythm affects glucose levels, and one study showed that exercising in the afternoon for two weeks with high intensity produced a shorter duration of improved glucose control. However, there is a lack of studies observing the more prolonged improvement of metabolic health with exercise during a specific time of day. 

 

The purpose of this study was to investigate whether exercising during the morning or afternoon can prolong the improvement of metabolic effects in patients with poor metabolic health. The analysis used data from the “Exercise training reduces intrahepatic lipid content in people with and people without nonalcoholic fatty liver” study. A total of 32 males at risk for diabetes were included in the study. The average age was 58 ± 7 years.  

Twelve (37.5%) of the male participants exercised for three months in the morning between 8.00–10.00 a.m., while 20 (62.5%) completed exercise during the three months between 3.00–6.00 p.m. In the morning group, 5 (33%) of the males had type 2 diabetes, 3 (25%) participants had nonalcoholic fatty liver disease, and 5 (33%) were considered obese. The afternoon group was comprised of 8 (40%) participants with type 2 diabetes, 6 (30%) males were obese, and 6 (30%) participants with nonalcoholic fatty liver disease. Participants with stage 2 hypertension, renal failure, and insulin or beta-blocker medication were excluded from this analysis. Unpaired Student T-test was utilized in the study to compare the timing of exercise for the primary and secondary outcome.  

The results showed that peripheral insulin sensitivity was better when males exercised in the afternoon (+5.2 ± 6.4 vs. −0.5 ± 5.4 μmol/min/kg FFM, p = 0.03). A decrease in fasting glucose levels was observed during the afternoon versus the morning (−0.3 ± 1.0 vs. +0.5 ± 0.8 mmol/l, p = 0.02). Exercise in the afternoon lowered fat mass by −1.2  ± 1.3 kg compared to −0.2 ± 1.0 kg by exercising in the morning (p = 0.03). There was a higher fat percentage in the morning group −0.3 ± 0.7% compared to the afternoon group −1.0 ± 0.9% (p  = 0.03). After adjusting for weight, maximal power output was higher in the afternoon with 0.40 ± 0.2 w/kg than in the morning with 0.24 ± 0.1 w/ kg (p  = 0.05). 

In conclusion, the participants that exercised during the afternoon observed more benefits that improved metabolic health. A few limitations were found in the study. One limitation was the study only included males, so the results are not generalizable for females. Further evaluation should explore the effect of metabolic effects during morning or afternoon exercise with females and males.  

Practice Pearls: 

  • Exercises performed during the afternoon provided more metabolic benefits for male participants with poor metabolic health. 
  • Participants exercising in the afternoon had a significantly enhanced peripheral insulin sensitivity compared to exercising in the morning (+5.2 ± 6.4 vs. −0.5 ± 5.4 μmol/min/kg FFM, p = 0.03). 
  • Additional benefits statistically significant in the study were reducing fat and glucose levels and better physical activity functioning. 

 

Mancilla, Rodrigo, et al. Exercise Training Elicits Superior Metabolic Effects When Performed in the Afternoon Compared to Morning in Metabolically Compromised Humans. Physiological Reports, vol. 8, no. 24, 2020, doi:10.14814/phy2.14669.  

Bureau, M. Afternoon Exercise Best for Blood Sugar Control in Those at Diabetes Risk: Study. Medical Dialogues, January 30, 2021.  

 

Alexis Dunn, PharmD. Candidate, Florida Agricultural & Mechanical University, College of Pharmacy and Pharmaceutical Sciences