Working out in the morning — especially on an empty stomach — is the best way to burn stored fat, making it ideal for weight loss. That’s largely because the body’s hormonal composition in the morning is set up to support that goal, says Anthony Hackney, a professor in the department of exercise and sport science at the University of North Carolina Chapel Hill.
“In the early morning hours, you have a hormonal profile that would predispose you to better metabolism of fat,” Hackney says.
People naturally have elevated levels of cortisol and growth hormone in the morning—both of which are involved in metabolism—so you’ll “draw more of your energy from your fat reserves,” Hackney says. That can potentially help with weight loss. Research also suggests that morning exercisers may have less of an appetite throughout the day, which could also help protect them from putting on pounds.