What you always wanted to know about macronutrient metabolism when working out!

QUESTION #1

Would you drive your car without gas? 

No… because you won’t get too far right?

Don’t forget to fill your tank

Then why would you exercise on an empty stomach…? Exercising when you are under-fueled is like running on fumes and results in sluggish performance. And additionally does not help you burn fat!

QUESTION #2

If I were to eat better, would I recover faster?

That is a complex question that now requires some deeper thought and explanation about food groups and their function…..

MACRONUTRIENTS
Energy is stored in the chemical bonds of macronutrients, as Carbohydrates, Fat and Protein. Carbohydrates and fat are your primary energy source, while amino acids from protein are used infrequently as a fuel source for physical activity. They are primarily used for structure, function and regulatory purposes.
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Healthy fats

Dietary fats are stored as triglycerides in adipose tissue and skeletal muscle.

Intramuscular triglycerides are an important fuel source especially during prolonged aerobic activity.
By weight, fats provide more than twice the amount of energy than carbohydrates or protein. Therefore this is an efficient way to store energy.
Dietary Carbohydrates are converted to glucose and stored in the liver as glycogen. Liver releases glucose as needed to maintain normal blood sugar. Glucose is then taken up by the brain and skeletal muscles. Glucose can then be used as an immediate energy source or stored in the liver and muscle tissue.
METABOLISM
Carbohydrate is the primary fuel source during physical activity and is transformed into carbohydrate storage areas. Carbs are ultimately stored as muscle & liver glycogen and blood glucose. Because these stores are limited, it is crucial to consume adequate amounts of carbohydrates on a daily basis in order to replenish your muscle and liver glycogen between daily training sessions. If you are exercising for 60 minutes or more
you need to balance water and energy output with enough fluid to match your sweat loss and enough carbs to provide energy and maintain your blood sugar levels.
Consuming carbohydrates prior to exercise helps your http://food.ndtv.com/health/benefits-of-oats-1234330performance by “topping off” the muscle and liver glycogen stores.
It is recommended that you consume 1.0 g/kg carbs 1 hour before moderately hard exercise or 2.0 g/kg 4 hours before.
Consuming a small amount of protein before exercise (such as a glass of milk or a yogurt) can optimize recovery by providing a “ready-and-waiting” supply of amino acids after exercise.
Consuming carbohydrates during exercise can improve performance by maintaining blood sugar levels. During a moderate to hard endurance workout, carbs supply ~50% of the energy. As you deplete carbohydrates from your muscle glycogen stores, your body relies on blood sugar for energy. It is recommended that consuming 100-250 kcal (25-60 g) of carbs per hour during endurance exercise (after the 1st hour) can increase stamina – this can be mixed between carbohydrate rich foods or fluids (such as energy drinks containing carbs).

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 Consuming carbohydrates  after glycogen-depleting exercise restores your muscle and liver glycogen and stimulates the release of insulin (hormone) helping to build muscles.
It is recommended to consume 1.5 g/kg immediately after exercise. If you’re not hungry it is recommended to consumer a high carbohydrate drink. Consuming carbs after your workout helps enhance the rate of muscle glycogen synthesis because the muscle cell is more likely to take up glucose, and because the muscle cells are more sensitive to the effects of insulin during this time, which promotes synthesis. Therefore eating the appropriate foods and fluids can affect your recovery.
ADDING PROTEIN
Adding protein to a post exercise carbohydrate meal may enhance glycogen repletion. It creates better muscle refueling and building response and reduces cortisol, a hormone that breaks down muscle. Having amino acids from protein readily available, enhances the building and repairing of muscles as well as reducing muscle soreness.Peanut butter toast
It is recommended to consume 10-20 g of protein after exercise!
Now this is not a “one size fits all” set of recommendations because everybody’s body shape and size are different. Not all individuals work out at the same rate of intensity, nor for the same amount of duration. These are basic recommendations and can obviously be “tweaked” to fit your individual needs!
Happy eating and exercising!
Randi Drasin, MS, RDN
Resources:
Nancy Clark “The Science of Eating for Sports Success”
Mary Dunford “Sports Nutrition: A Practice Manual for Professionals 4th Edition”