The question of the day: What time of day should I work out?

Well I'll break it down for you with three easy points.  There is no "magic" time, but if you consider the following three points in order of importance (#1 being the most important) then you'll be good to go!

1). (MOST IMPORTANT!) Pick a time that you can commit to.
I know, that sounds like a cop out, but it's simple math.  If you workout, you burn calories.  If you don't workout, you don't burn calories.  So, pick a time that you know you will actually workout.  If you read in Men's Health magazine that Hugh Jackman drinks a protein shake at 4:00 am, and then works out at 6:00 a.m., but you are not a morning person and will never actually get up, I advise you to not make your workout time 6:00 a.m.!  If you know once the day hits 3:00 p.m., you start crashing and it isn't in your genetic make up to workout after 5:00 p.m., don't schedule late afternoon workouts because you read it is good for you to workout right before dinner.  Pick a time that works for YOU.  Put it on your calendar and make it an appointment.  

Oddly, for me that time is 11:00 a.m.  I've tried the early morning thing and I tend to just let it go if I wait until the afternoon.  So on days when I schedule my workout for 11:00 a.m., I'm about 100% more likely to actually do it!

2) Pick a time at least 2 hours after your last meal
The notion that you should eat your food and then "burn it off" is a faulty one.  When you are digesting food in your stomach, blood is rushing down there to help with the digestion, and less if available to fuel the muscles during the workout.  LIkewise, having a full stomach can lead to GI distress during the workout.  Plus, your body always stores energy more efficiently after a workout, and less is stored as fat!  It is working on "resetting" everything to pre-workout levels.  Carbs get stored as glycogen in the muscles, protein is used to rebuild muscle tissue.  Some bodybuilders live by the concept of eating almost 50% of the day's calories in the short hours after your weight lifting routine.  That might be a little extreme, but it is the right idea.  

If you need some pre-workout energy, simple carbs are the way to go, throw a little recovery drink in your water bottle, or 1 hour before working out have a piece of toast, or some crackers, (under 100 calories).  Or you can try the new energy and endurance formula from Beachbody:  If you are having a bigger meal, make sure to wait at least two hours before working out, meals heavy in protein and fat, possibly as much as four hours.

3) (Least important, but still a factor) In general, earlier in the day is better
There is a notion that working out first thing in the morning means you will burn more fat.  This is partially true, but not as extreme as we'd like to think it is.  Your bloodstream can only carry about 20 kCal (Calories) of glucose in it to use for energy.  So when people say working out on an empty stomach, you burn more fat because there is low blood glucose, the amount in your bloodstream is pretty negligible.  Perhaps your glycogen stores are a little lower because of "fasting" during the night, but not enough to shoot your body into ketosis (burning fat in the absence of carbohydrate) in even an hour, unless you are on some kind of Atkin's/no-carb diet.  You don't want to be in ketosis during the workout anyway, that can compromise your form and energy level.  So these factors of burning more fat are not necessarily that important when you workout first thing in the morning.

The metabolic effects of working out earlier might be somewhat significant.  You often here working out early "kickstarts your metabolism."  If you are doing a HIIT workout, like TurboFire or Insanity, or a weight training workout with heavy weights, you might experience some of what we call EPOC, excess post-exercise oxygen consumption.  When you start working really hard, there is a slight lag from when you start to when oxygen becomes available for usage in the workout.  This lag at the beginning of the exercise means even when you stop working out, your body is trying "catch up" and will continue to deliver oxygen to the muscles.  This effect, plus the amount of energy your body puts into repairing muscles, reducing core temperature, and generally "resetting" the body to pre-workout levels will actually burn some extra calories throughout the day, particularly if you do it earlier in the day and then are semi-active during the day.

One final consideration is the body's cortisol cycle.  Cortisol is a "stress" hormone that is released when we are under either emotional or physical stress.  In general, the body wakes up and cortisol levels rise in the morning, peak sometime around the early afternon and then begin to go down.  When you workout late in the day, you actually cause cortisol to spike again, workouts create a lot of "stress" on the body.  Cortisol has a reputation for being an evil catabolic muscle eater, when in reality it is a necessary response in the body.  That being said, it does have catabolic effects on muscle and can cause you to retain water, both of which are undesireable if you are trying to lower you body fat % and look toned.  So while the effects are not extremely pronounced, it is a little better to fall within the body's cortisol cycle and have levels raise up from your workout sometime around the peak of the cycle, mid morning or early afternoon.  Hmmm looks like my 11:00 a.m. workout might actually be good for multiple reasons!

So remember, rule number 1 is the most important!!  But if you have the luxury of being able to choose your workout time more closely, consider rules 2 and 3 as well and it will help tweak your results!