Fueling your body for activity

This week I’m going to head onto a slippery slope of information about how your body uses fuel for energy. I am no expert on this subject, but I have spent a lot of time over the past six years trying to get a good understanding on proper fueling for my active lifestyle.

Over the last few years, I have written about fueling with complex carbohydrates, proteins, fats and the effects of various forms of sugar on your body. I have also discussed what it takes to make your body a fat burner vs. a carb burner. In the mix of all this information, the actual process of converting fuel to energy in our bodies has not been very clear.

Elite athletes and fitness professionals have a very good understanding of what is called bioenergetics or the fueling and energy conversion that occurs within our body during exercise. Please keep in mind the science around fueling the human body is extremely complex; too much detail would make for a very long and dry FIT for Life column.

For the sake of keeping this simple, fueling our body starts with three basic food sources that we know pretty well, being carbohydrates, proteins and fats. The key sources of energy from these food sources which are broken down during digestion are amino acids from protein, monosaccharides, disaccharides, polysaccharides (sugar) from carbohydrates and fatty acids from fats. Perhaps that’s an oversimplification of the process, but one I think is easier to understand.

Once the digestive process breaks down the various components from carbohydrates, proteins and/or fats, they are ultimately converted into adenosine triphosphate or ATP. ATP is how your cells get energy to function, via the transport of chemical energy within cells, which generates metabolism. These high-energy molecules derived from the foods we eat drive your metabolism to maintain proper cell function and physical activity.

The three actual systems responsible for fueling our bioenergetic processes and supporting your metabolic energy during exercise or just going about your day to day activity breaks down like this:

• Adenosine triphosphate–creatine phosphate (ATP-CP) system supports high intensity physical exertion for a very short duration anaerobic activity such as interval, sprinting, circuit style training requiring quick bursts of energy lasting 10 seconds or less.

• Glycolysis system supports moderate to high intensity physical activity that requires shorter bursts of energy. Glycolysis allows for a greater amount of energy release than ATP-CP, but it is also limited to roughly 30 to 50 seconds in duration. An average gym workout requirement tends to place a greater stress on Glycolysis fuel delivery since most gym exercises fall in the 30- to 50-second range.

• Oxidative system supports longer, lower-intensity activities such as endurance running, vigorous walking and cycling, for example. It is the oxidative system that relies heavily on carbs and more importantly, burning fat when the activity exceeds 20 minutes on average. The oxidative generates energy slower than the other two systems and relies on great amounts of oxygen intake during the activity over time.

Now the real question around fueling your body for exercise and an active lifestyle is how do bioenergetics apply to each of us? Since these various systems, chemical interactions and complexities leading to ATP fueling at a cellular level are extremely detailed, let’s just look at how it relates to being active.

What’s important to understand is all three types of macronutrients — carbs, protein and fats — play key roles in fueling your body. Too much of any one of these macronutrients can throw off your body’s ability to fuel properly. When macronutrients are out of balance, weight gain can occur and health problems can come into play.

For example, carb loading is an idea that you can fill your liver and muscles with glycogen (sugar) prior to long duration exercise or competition. Not everyone will agree with me, but carb loading has not consistently proven to be an effective way for all active people to prepare and fuel their oxidative system for extended physical activity. It is just one way for experienced athletes to prepare fueling for endurance types of activity. In fact, as we know, fat is far more effectively stored in the body and our oxidative system will use fat as it does carbs. This is where turning your body into a fat-burning machine can come into play by reducing your carbohydrate consumption as another form of fueling.

The other important aspect to the three bioenergetics systems ATP-CP, Glycolysis and Oxidative is they work as a team. Each has a role to play in the distribution of on-demand energy flow to the body. As humans evolve, our internal systems have become very good at tapping quick on demand energy to handle a fight or flight scenario by using ATP-CP. The other example at the opposite end of the fueling spectrum is our Oxidative system which developed to support long distances traveled as migratory hunters and gatherers.

The three systems work around anaerobic and aerobic activities depending on effort and length of time. When it comes to glycolysis, which is an anaerobic based fueling system, it is most often used in short gym type workouts. Our bodies use glucose metabolized into a substance called pyruvate. Think about weight lifting and your breathing is restrained, your muscles run low on oxygen; pyruvate gets broken down as fuel for quick short-term energy feeding musculature demands.

The anaerobic process around pyruvate comes with a downside to fueling high intensity burst of physical activity. When the body demands and converts the pyruvate, it in turn becomes a substance called lactate. When too much lactate develops, the acidity levels inside the muscle cells occur and impact many of the metabolic pathways that help your body convert glucose to energy. As most of you know, high lactate levels in your muscles cause the familiar burning sensation during intense physical activity. This burning sensation is your body’s way of preventing injury or damage by slowing the mechanics of muscle contractions.

As you can see, fueling the body is a complex set of factors. Many of the factors involved I have not touched on for the sake of simple understanding and limited word count for my column. The last bit of information comes in the form of three unknowns for you to find answers to which are specific to the individual and what they are doing.

Here’s the question and it’s pretty straightforward: How much do I need to eat to fuel my activity?

The first unknown is, how many calories is your body going to require? This will depend on your height, weight and physical conditioning. You should also factor in your general metabolism and current nutritional behavior.

The second unknown that you will need to calculate is based on the type of physical activity. Weight training will require different needs over training for a triathlon. Understand and fuel for the type of activity. Is it more anaerobic or aerobic in nature, for example?

The third and final aspect to consider is intensity of the activity. Intensity needs to be considered around how long and how much effort will be required for the activity. This will correlate to calories burned at what level of effort over time.

Here is a fair and accurate example: If you have ever been on a treadmill, you see a digital readout of calories burned. This is based on a calculation that for every mile you walk or run, you’ll burn about 100 calories. If you’re on a bike, the average person burns around 400 calories an hour. There are a number of good reference charts that can help you figure out other forms of exercise and activities to find a benchmark. Once you have this benchmark, you can calculate how far or how long and come up with a good calorie count for fueling your efforts.

The study of bioenergetics in the human body has become a very exact science. These complex processes of chemical energy (food) being converted to releasing energy that is utilized to do everything from heal the body to movement and muscle contractions are essential to all of us. When you have balanced nutrition and make an effort to fuel to your specific activity, you will be surprised how it can enhance your effort and really help with your lifestyle and fitness goals.

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Judd Jones is a director at the Hagadone Corporation in Coeur d’Alene.