According to science, both morning and evening workouts have their own benefits.
Training in the morning:
Training in the morning is the best to lose weight. In fact, exercise right after waking up helps to control appetite and improve glucose tolerance and insulin sensitivity.
Also, morning workouts can help to sleep longer and go through deeper sleep cycles when compared to exercising at other times of the day. The morning group that participated in the studies spent up to 75 percent more time in the deep sleep stage at night.
Some other studies proved that there is no difference between morning and evening training, but maybe training in the morning is the best time for maintaining a consistent workout schedule since Gyms are usually empty and there is no after-work duties.
Training in the evening:
But if you trust yourself to stay consistent, the evening has plenty of benefits too. Your core body temperature raises throughout the day, and since warmer muscles are more flexible and at less risk of injury, that makes evening a great time for higher-intensity exercise
A 2009 study published in the Journal of Strength and Conditioning Research found there are greater gains in muscle size when trainers work out during the evening hours. A group of young men were trained between 5 p.m. and 7 p.m. for the first 10 weeks of the study. Then, for the next 10 weeks, the men were divided into two groups: a morning group (7 a.m. to 9 a.m.) and an afternoon group (5 p.m. to 7 p.m.). The researchers found all men gained size and strength, but the afternoon group gained an average of 3.5 percent more, compared to 2.7 percent more in the morning group.
Also the studies showed that afternoon is better for high-intensity exercises, such as swimming, running, or biking, rather than walking. In part, this is because core body temperature is higher in the afternoon, which means muscles and joints are readier for exercise — there’s also a lower chance of getting injured at this time.