Does the Time of Day You Exercise Affect Weight Loss?

Exercise benefits everyone’s health, but does the time of day you exercise matter for weight loss?

It’s not a simple question to answer, but if your goal is to lose body fat, making a habit of exercising in the morning may give you an edge.

What the Research Found

A study by researchers at the Karolinska Institute in Sweden and the University of Copenhagen in Denmark found that morning exercise activates metabolism more than exercise later in the day, which may help with fat burning. The research, conducted on mice, found that morning exercise helped burn excess fat around the abdomen and waist compared to exercise in the afternoon or evening.

The researchers noted that physical activity affects the body differently depending on the time of day, largely because of the body’s internal clock. According to the study authors, the results suggest that morning exercise may be more effective than evening exercise for burning fat and improving metabolism, and that timing plays a role in the body’s energy balance. The researchers were clear that further research in humans is needed to confirm these findings, since the study was conducted on mice rather than people. The results were published in the journal PNAS.

A Related Study on Insulin Resistance

Separately, a November 2022 study from Leiden University Medical Center in the Netherlands reported that exercising anytime between noon and midnight was associated with a lower risk of insulin resistance in humans. Insulin resistance occurs when muscle, fat, and liver cells have difficulty responding to insulin, which can cause blood glucose levels to rise; left uncontrolled over time, this can lead to type 2 diabetes. The study found that physical activity between noon and night was associated with reduced liver fat as well as reduced insulin resistance. The results were published in the journal Diabetologia.

This article summarizes findings from scientific studies for general interest and is not medical advice. If you have specific health concerns or are considering a new exercise routine, it’s a good idea to speak with a doctor.