The Best Time to Workout

Written by John Fawkes

Personal trainers will tell you that the busiest time of day in any gym is early in the morning, between 6 and 9 a.m.

Some people work out in the morning because it’s convenient — it’s when they have the most energy, and morning workouts fit their schedule. Many others, though, work out with the sunrise because they believe morning workouts are more productive and burn more fat.

But do they? 

The Rationale of Early Morning Workouts

There are two reasons why early morning is widely considered the best time to work out.

First, your testosterone levels are at their highest early in the morning. Testosterone levels rise throughout the night, typically peaking around 8 a.m. before starting to fall again.

Second, when you work out in the morning, particularly on an empty stomach, you’ll burn more fat during your workout. The reason for this is that your stores of glycogen — the form in which your muscles and liver store sugar — will be partly depleted after not eating for 12 hours, thus forcing your body to start burning fat for energy.  

Both of these reasons for exercising in the morning make perfect sense. They both sound right. It’s just that studies say otherwise.  

Why Science Says Afternoon and Evening Workouts Are Superior

A 2013 study published in the journal Biological Rhythm Research demonstrated that muscle anabolic signaling — the body’s way of telling the muscles to grow —is higher in the evening than in the morning. In line with this, a 2016 study by a team of Finnish researchers found that afternoon and evening workouts produced more muscle growth than morning workouts.  

Finally, a study at the University of Southern Mississippi found that bodybuilders who trained in the evening gained more muscle than those who trained in the morning. The evening trainees also lost fat, while the morning trainees gained fat.

So if morning workouts burn more fat and testosterone is highest in the morning, why is evening training superior?

It is true that training on an empty stomach burns more fat during the workout, but this misses an important point: energy is energy. If you train on a full stomach, your body will simply burn fat later in the day. What matters is your total energy balance for the day.  

That’s why studies on the effects of fasting training vs. eating before exercising have consistently shown that eating before a workout leads to more energy burned during the workout — and also more muscle growth and better appetite control.

As for testosterone, while it’s true that it is highest in the morning, it’s also responsible for recovery from exercise, so it should be high after your workouts as well. So it makes more sense to work out in the evening, when testosterone begins to rise.

Furthermore, the stress hormone cortisol is highest in the morning, impairing recovery from exercise. The testosterone/cortisol ratio — an indicator of your ability to recover from exertion — is highest in the later afternoon and early evening.  

There’s also a third factor that’s rarely discussed: body temperature. Your core body temperature is highest in the evening. That means more blood flow, a faster metabolism and greater mental alertness.

None of this changes the fact that you need to train when you have the time and energy for it — and for many people, that is the morning. But science says that all other things being equal, training in the later afternoon and early evening is better than training in the morning.

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