Some people do aerobic exercise first thing, before they’ve eaten, because they think it will help them burn more fat. There is some evidence that this practice, sometimes called “fasted cardio,” may boost fat burning — but only fleetingly. Over the course of days or weeks (which is what counts), research shows that it doesn’t seem to offer any advantages. For example, in a four-week trial that randomly assigned young women to either fast or drink a 250-calorie shake before their aerobic workouts (while otherwise eating a low-calorie diet), both groups lost the same amount of fat and weight. Similarly, a study involving overweight women who did high-intensity interval workouts for six weeks after either fasting or eating found no differences in fat loss.
All in all, the best time to work out is whenever you can. If you exercise at different times of the day, be sure to note the hour as you’re tracking your progress. That way, you’ll know when your body clock may be to blame for a less-than-optimal workout.
— Robert J. Davis
Adapted from “Fitter Faster: The Smart Way to Get in Shape in Just Minutes a Day.”
Adapted from https://www.washingtonpost.com/national/health-science/what-is-the-best-time-of-day-to-exercise-its-not-when-you-think/2017/06/16/2020c3ba-51cf-11e7-be25-3a519335381c_story.html?utm_term=.65bc4f5ef6f2