Conventional wisdom—and flocks of lean early birds—argue that a morning workout is best. You’re more likely to exercise consistently, burn fat preferentially, and stoke your metabolism for the whole day, so the logic goes. But, the early morning sweat sesh isn’t for everyone, including many of those who slog through it every day. You can click here for reviews into archives of different workouts, products and tips and tricks.

Exercise Motivation

Research suggests that those who work out in the morning are more likely to keep at it over the long haul. However, it stands to reason that the type of person who gets up before work to exercise is more likely to be disciplined in their lives in general. A morning workout doesn’t confer discipline; it’s the byproduct of it.

Burning Fat First?

When you exercise in a semi-fasted state—before breakfast for example—you have reduced muscle glycogen and depleted liver glycogen, which would normally fuel your workout. With limited glycogen stores, your body reaches to stored fat and, to a limited extent, amino acids in your muscles for energy. But, at the end of the day, literally, it’s the total amount of energy burned that matters.

Reduced Performance

Let’s say you wake up bright and early for a morning run and log 30 minutes at a pace of 6 miles per hour, burning 307 calories before hunger drives you home. Compare that to exercising in a fueled state—in the afternoon, for example—when you may log 30 minutes at 8 miles per hour. The latter workout burns over 100 additional calories. Even if you were to sustain an equivalent pace in the morning and afternoon workouts, both would burn the same relative amount of total energy.

Sleep Deprivation

With its regulatory effect on appetite, leptin is a master hormone, according to UCLA professor Aaron Blaisdale PhD. When you skimp on sleep, your body reduces leptin concentrations and churns out ghrelin, a hormone that increases your appetite. Even, dragging yourself out of bed a couple hours before you’re sufficiently rested can negatively impact your hormone levels. Increased cravings are hardly the payback you’d expect from your healthy habit. According to a prospective study published in the journal Sleep Medicine Reviews, sleep durations less than seven hours contributed to increased risk of obesity. 

Best Time of Day to Exercise

According to Kari Hartel, RD, LD, because your body temperature is highest and you’re most alert in the afternoon, you’re less susceptible to injury and more likely to have a good workout. However, the expert consensus is that the best time of day to work out is the time that you’re most likely to actually do it. If you do choose to exercise in the morning, make sure you’re well-rested and warm-up your muscles with active stretches and foam rolling to prevent injury.