Fueling The Machine (Interview with Sean Newsom)

By Danny Mackey  M.S.

 

Track and Field is a great sport because every little decision we make can have an outcome on our performance (though that aspect of this sport can prove cruel and frustrating at times).   One of the biggest “little” decisions we make daily that can affect our running is what we eat.  In a time where fad diets instantly go viral on the web and diet books dominant the health section of a book store, it is difficult to figure out if the information is actually based on science.  Now consider that athletes of all levels live in a reality where inches and seconds matter.  It makes that decision of PB&J or Ham sandwich for lunch a little more interesting.  If you look back at an article I wrote last year: http://www.flotrack.org/articles/view/733-will-run-for-food I give some foundational nutrition information.  Here we will take nutrition one step further and get more specific, because I was lucky enough to have an expert on hand.

 

            The expert is Sean Newsom.  Sean went to undergrad at Michigan State, earned his MS from Colorado State and is now working on a PhD at the University of Michigan.  He is a great resource not only because he can talk about hepatic VLDL-triacyglycerol secretion like he can the Detroit Red Wings, it is also because he has raced and is a fan of track and field (oh yeah and Sean also knew about Flotrack before this interview).  Sean works in the Substrate Metabolism Laboratory at U of M and recently published the paper “Energy deficit after exercise augments lipid mobilization but does not contribute to the exercise-induced increase in insulin sensitivity” in the Journal of Applied Physiology 108:554-560, 2010.

 

Sean can you give us a short summary of your article?  How about even shorter than the title?

            The main issue we were exploring in this study was how diet could modify the effect of a single bout of exercise.  The long and short of it is that diet, as in both energy intake and macronutrient balance, is often poorly controlled or even neglected entirely in many health-related exercise physiology studies.  The take home message for the people reading this interview is that what you eat after exercise can affect how your body responds to the exercise.

 

So in other words, what we eat after our run will affect us?

            Exactly. And for the most part athletes have some idea of what it means to eat a balanced, healthy diet.  Most athletes know they know they are better off choosing apples over fries, but there is obviously more to it than that.

 

Carbohydrates, Fats and Proteins are the macronutrients we see on the back of food labels.  There is an Atkins diet granola bar, low carb candy and even protein water.  What do you think this means for athletes?

It means there is certainly not a lack of unique food options, foods are not always as they may seem, and finding what is best for yourself can definitely be confusing.  Keeping it simple, I would advise any runner to consider carbohydrate one of the major keys to success.  Our bodies seem to be very well conditioned to perform at high intensities while using carbohydrate as a main source of energy.  If you are using it, make sure you are replacing it!

 

What about for weight loss?  Runners typically have an ideal weight where he or she performs best, does the macronutrient content influence weight?

There seems to be a lot of misinformation surrounding this issue.  In terms of weight loss/maintenance/gain….macronutrient content is really not the issue.  It is the balance of caloric intake and caloric expenditure that matters. A common application of this misconception is the “friend that lost lots of weight on a low carbohydrate diet.”  First, glycogen, the stored form of carbohydrate, has water-retaining properties, so when you are carbohydrate depleted, you lose water weight.  Second, back when the low carbohydrate diet first became popular there was not aisle upon aisle of low carbohydrate diet foods available.  So, basically people who initially followed this type of diet were likely eating fewer calories and that will definitely result in weight loss.  As a runner, this is probably not your best option because if you start cutting out carbohydrates in an effort to lose weight, you may have trouble performing at your best during intense workouts.  Subtle reduction of all macronutrients, with saturated fats taking the lead, is definitely a much better way to go.

 

What about the thought that protein is an “inefficient” calorie?  In other words, we are not effective at using protein so we can eat more, feel full, but not necessarily store the excess calories.

            That is an interesting question, you will hear this sort of argument often when discussing weight loss.  While there is a lot of interesting ideas related to protein consumption, simply put, I would be more inclined to argue that the human body is well adapted to harness energy from food, even when we consume a relatively high protein diet.  The bottom line is that if you eat more calories than you need, protein or otherwise, you are going to put on weight.  The opposite is also true.  There is not likely any miracle advantage associated with protein consumption.

 

Ok, so let’s talk about carbohydrates some more.  Can you give us some background on why they are so important?

            Take a marathoner that runs 16 miles on a Monday.  Let’s say this runner is trying to lose weight, so he/she is restricting caloric intake, and this runner decides to cut down on their carbohydrate intake.  As a result, they now have slightly lower muscle glycogen in reserve for Tuesday.  He/she does a hard workout Tuesday.  Now keep in mind, the more intense the aerobic/anaerobic activity the more we tap into this stored carbohydrate for energy, because this allows us to get ATP for energy very quickly. Continuing this carbohydrate restriction on Tuesday, this runner is likely to be more in hole for muscle glycogen storage…  follow this routine all the way to Saturday…  When this marathoner attempts a long hard session he/she will probably feel sluggish, especially as the workout progresses in duration, and this runner is much more likely to “bonk.”

 

So carbs are really king.  But, if an endurance athlete is trying to maintain muscle mass, while keeping a light weight, will they be in trouble if he or she cuts protein intake too low?

            Protein is obviously very important for a number of reasons, but in general we tend to be a little overly obsessed with consuming protein.  Most Americans, athletes or not, tend to consume enough protein to maintain lean mass without even consciously attempting to do so… With that in mind, for most athletes, a slight reduction in protein intake is going to have little effect on their ability to maintain lean mass.  As a very related point of interest, insulin is also very important for the building or maintaining muscle mass because insulin helps regulate the activity of mTOR, a major regulator of protein synthesis.  This is just one more reason to be sure to consume carbohydrate after any run… in combination with some essential amino acids, it’s like hitting the gas pedal on protein synthesis.

 

Other than eating the proper amount of protein, fat and carbohydrates to perform well, timing of the meal after exercise is also important correct?

            Very important.  After exercise you will have a net breakdown of muscle protein if you do not eat or do not eat the right foods, such as the essential amino acids and carbohydrates.  Also, our body is more or less primed to refuel/recharge after exercise, so we are missing a huge opportunity to recover if we do not eat soon after training.  As our muscle glycogen stores become depleted, our body appears capable of recognizing this, and there seems to be an interaction between glycogen and the cell’s energy sensor AMPK.  While it is still not entirely mechanistically clear if this is what drives post-exercise restoration of muscle glycogen, etc., it is very obvious that after exercise a runner has essentially primed the pump to restore muscle glycogen stores, turn on protein synthesis to repair the muscles, etc.  So I say as soon as you can get your hands on food, get it in.  In fact, it is always a good idea to plan for these post-exercise meals so that you are getting the right foods in ASAP.

 

 

I want to thank Sean for his time giving the interview.  As you all read this there should be a few take home points.

 

Pay attention to your caloric intake and macronutrient breakdown.  You can even do a 3 day assessment as there are multiple nutrition logs online like this: http://www.thedailyplate.com/

Also, make sure you talk to a nutritionist or an exercise physiologist before you start cutting weight.  As you read above, something like the Atkins Diet will probably not be the best thing for improving that 5k PR.  Finally, make sure you get something in after the run.  I personally have trouble with this because I work and train.  As a result, I have this nasty 400 calorie drink with 80 grams of carbs and 20 grams of protein that I drink if I do not have time for a real meal. 

And now you know something may be better than nothing.