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Thursday, January 20, 2011

Should Post Workout Meal Vary on Cardio and Strength Days?

Thanks to all who posted questions for blog topics.  I was most intrigued by the question posed by my friend Michele:  "What should you eat for dinner after a cardio workout?  After a strength training workout?"  My initial reaction and hunch was that your dinner choice shouldn't much change based on whether you did cardio or strength training.  But it got me thinking.  Would the TYPE of activity affect your post workout meal?

Of course, there are MANY variables that we'll have to take into account.  Let's assume this question applies to someone who works out after work before going home.  Let's also assume this person's primary goal is fat loss (as opposed to muscle hypertrophy).

Cardio vs. strength training


As I wrote in earlier posts, strength training has been scientifically proven more effective in promoting fat loss and muscle gains than aerobic activity alone.  But for those of us who work out 5 or 6 days a week, there are going to be non-strength days where the workout may be predominantly "cardio".  The next question we need to answer:  is the "cardio" workout a High Intensity Interval Training workout (this would actually be an anaerobic workout) or a more sustained, endurance cardio session at a more moderate intensity?

For simplicity's sake, let's put the High Intensity Interval workout and strength training workout in the same category (anaerobic) and the longer, more sustained aerobic workout at a more moderate intensity workout in another (aerobic).  It is true that these different type workouts draw from the body's energy stores in different ways.  Anaerobic activity uses energy predominantly from muscle glycogen.  Without getting too scientific, muscle glycogen is your body's readily available energy stores that have been converted from the carbohydrates you've consumed in your previous couple of meals.  Aerobic activity uses about 50% muscle glycogen stores.  (Stick with me here, because this is important and will clear up the myths surrounding "low carb diets" and "cardio burns stored body fat".)  Duration of exercise affects the amount of glycogen used for energy.  As the duration of activity increases, available glycogen diminishes, increasing the reliance on fat stores as a fuel source.

This does not mean that the best way to lose body fat is to perform low-intensity activities for a long duration!!!  Bottom line is, if the workout contributes to a caloric deficit, the body will draw on its fat stores at some point to make up for the deficit.  Remember, that higher intensity workouts (anaerobic) lead to higher EPOC levels (Excess Post Oxygen Consumption - read earlier posts on Intensity Level and HIIT).  In other words, when you work out at higher intensities, your body's metabolism remains revved up for a much longer period of time post-workout.

So, it's an intriguing question  -- should your post-workout meal be different based on they type of workout, since aerobic and anaerobic workouts draw different percentages from glycogen and fat stores?  My short answer is no.

Basically, when exercising aerobically at a more moderate level (as opposed to higher intensity strength and HIIT), you will be able to exercise for a longer period (while you may strength train for 45 minutes, if you subtract rest periods between sets your actual workout time is more like 15-20 minutes, albeit at a much higher intensity).  Because you are working out for a longer duration, your glycogen stores run out and your body taps into its fat stores for energy.  This does not mean the total calories burned is greater.

When you've finished either type of workout your body is glycogen depleted and should be fed carbohydrates and protein within 30 minutes of completion of workout.  It is recommended that consuming 1.5 grams of carbohydrate per kg of body weight within 30 minutes of completing exercise in order to maximize glycogen replenishment.  How much protein post workout?  Between .25 and .50 g/kg body weight, depending on your goals (10-40g).  I say this goes whether it was an aerobic or anaerobic workout.

Carbohydrates have gotten a very bad rap in recent years and much of the hype surrounding the "low-carb" craze is bullshit.  The fact is that maximum fat utilization cannot occur without sufficient carbohydrates.  In other words, you need carbs to burn fat.  So, it all boils down to total calories in versus total calories out.  The most scientifically sound breakdown of macronutrients is 50-70% carbohydrates, 15-30% protein, and 10-30% fat.  The bottom line is that you want all of your meals to include this macronutrient breakdown (except for your immediate post-workout, which I will get to in a minute).   As already stated, carbohydrates is the main energy source the body uses for all physical and mental tasks.  That's why your body craves carbohydrates if you do not get enough.  For the most part, I am talking about complex carbohydrates that are high in fiber (except post-workout).  Protein is important for building and maintaining muscle tissue.  Best sources of protein are from animal sources (sorry vegans) because they contain all of the essential amino acids needed to rebuild lean tissue.  Chicken, fish, meat, eggs are best whole food proteins.  Finally, fat.  Fat is important is important because it stimulates the release of the hormone CCK in the body, which signals satiety (feeling full).

The ultimate goal for the layman (or woman) with each meal is to find the appropriate breakdown of carbs, protein, and fats so that you are able to eat a reasonable amount of food without feeling the need to go overboard.  When the optimal breakdown of the macronutrients is attained, you'll be full without consuming too many calories.  I know this is a very simplistic explanation, but I find that people are all over the place with the information that's out there and most people are just confused.  Ultimately, you have to listen to your body, knowing the physical demands you place on it (amount of exercise), and feed accordingly.  I'm not getting too in-depth with what foods are "good" and "bad" because I'm pretty certain most of you reading this know what's good and bad.

Oh, back to the post workout meal!  Even if you are working out after work and before dinner, you do yourself (and your metabolism) a huge favor by taking a post-workout drink that includes carbohydrates and protein within 30 minutes of finishing your workout.  The sooner the better.  When you are glycogen depleted (as you are post-exercise) your body does whatever it can to refuel.  In the absence of immediate post-workout carbohydrates, the body will use amino acids (found in your muscles) and convert it to energy.  This is bad.  Essentially, this is the body breaking down muscle tissue (for which you've been working hard, by the way) to use for energy because there's no more glycogen (carbohydrates).

I know this can get complicated.  But the bottom line is this:  no matter when you workout, you should immediately replenish your body with a post-workout drink/shake that includes simple carbohydrates and a fast-acting protein (since timing is important here, a powdered protein supplement is recommended because it will be absorbed much more quickly than whole food protein).  I use apple juice to mix vanilla whey protein (whey protein is found to be the most complete, that is, contains most of the essential amino acids needed to build muscle).  You do not need to have the usual breakdown of fat in this post workout drink or shake.  Fat is absorbed and digested quite slowly.  This is good for your other meals, but not so good for your immediately post-workout meal (drink) since you want your body to absorb nutrients very quickly.

To take it a step further, I recommend listening to your body on the different days you work out.  If you are doing a lower intensity day, you'll burn fewer calories with your workout, and therefore require fewer calories hit the "break even point".  If you've had a very intense workout, you'll require more calories.  On days before I know I'll be having an intense workout, I know it's okay to eat a bit more heartily than I would if I know I'll be having a light or no workout.  My body tells me so.  I've learned through the years that I can modulate my caloric intake on a daily basis according to the demands I've placed on my body.

So, my advice is to be sure you get a post-workout drink that includes carbohydrates and protein (ideally, whey) as you leave the gym.  If you are worried about those drinks having too many calories (as many of my women clients are) then simply cut back the 200 or 300 calories from the dinner you'll have an hour or two later.  What's for dinner?  50-70% carbs, 15-30% protein, and 10-30% fat.  An ideal dinner could be a boneless, skinless chicken breast (grilled or baked) with a boiled sweet potato and broccoli (lightly sauteed in olive oil for "good fat") with a side of avocado (also good fat).  As for those ranges (50-70% carbs, for example), again, listen to your body.  If you find yourself sluggish all day leading into your workout, try upping your carbohydrate intake.  If you find yourself hungry within an hour or two of eating, try upping your fat intake (mono- and poly-unsaturated, not saturated).

I know the diet posts can be wonky and boring, but I think it's important that people get a handle on the basics of nutrition amidst the misinformation out there.  Thanks for the spark, Michele!

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