Why the same workout works better before breakfast than after work

A study from Appalachian State University found that people who exercise first thing in the morning fall asleep faster and sleep with fewer disruptions than people who work out later in the day. One possible reason, researchers suggest, is that the body releases stress hormones upon waking, and moving your body early may counteract them, whereas exercising later gives those hormones more time to build up. Other research is more mixed. One study found that vigorous exercise before breakfast helps counter the blood-sugar effects of a high-fat diet, while a separate study found people performed better after eating a light breakfast first. Vanderkam's own reading of this research settles on a simpler, less biological reason mornings win: people who exercise early are simply more likely to keep exercising at all, for the same reasons mornings work well for anything requiring self-discipline. As triathlon coach Gordo Byrn told her, there's always a reason to skip a four o'clock workout, and it's going to be a good reason, too. By evening, deadlines, fatigue, and a hundred small emergencies have had all day to accumulate.

Vanderkam tested this on herself. After moving from Manhattan to suburban Pennsylvania, she began running at dawn on days her husband was home, laying her clothes out down to the ponytail holder and setting her alarm for 6:20 so she could be out the door within ten minutes. Running the same trails morning after morning, pregnant at the time and grateful for the shade of thick summer leaves, she started to see real progress, including finally running up a switchback hill without stopping. She watched earthworms cross the pavement, startled deer in the woods, and once caught a rainbow just as she turned for home. The running itself mattered less, she found, than the fact that doing it at dawn made it nearly impossible to skip. A single run changes nothing. Months of runs, protected by the hour they happened in, changed her fitness and, she suspected, her mood.

Choose a morning window for your workout, ideally before the day has any chance to throw an emergency at you, since evening plans are the ones that get cancelled by late meetings and tired excuses. The night before, lay out everything you'll need, clothes, shoes, water bottle, so the only decision left when the alarm rings is whether to get up, not what to wear. Start with something short enough that you'll actually finish it and want to repeat it tomorrow, rather than an ambitious session that leaves you dreading the next one. Then measure your progress in weeks and months rather than in any single workout, because a single run does very little, while the same short run repeated for a season quietly rebuilds your fitness.