How The Body Burns Carbs

But first, how does it get in there…

Now, how to burn it! Compared to fats and proteins, carbohydrates offer a muscle pure sugar that it can use to produce energy, or ATP. Muscles (and the rest of your body) can still use fats and proteins to produce energy, usually by converting them into useable forms of sugars, fats or amino acids, but this process takes a longer time to complete and isn’t your bodies preferred form of making energy for high-intensity exercise.

What Happens Without Carbohydrates

So what happens if you’re completely carbohydrate depleted, and your body has no sugar to burn? First, you find it more difficult to produce an intense contraction, like a maximum bench press or an all-out sprint. Second, your motivation to exercise begins to drop, since carbohydrates boost tryptophan levels. Tryptophan assists with serotonin synthesis, and serotonin synthesis improves you mood and motivation. As a matter of fact, researchers from Arizona State University found that a very low carbohydrate diet significantly enhanced fatigue and reduced the desire to exercise in overweight adults.

But there are three problems with most studies that show carbohydrates to be important for quality of exercise or motivation to exercise:

  1. they don’t allow the subjects in the studies ample time to adapt to a low carbohydrate diet, which can take several weeks or even months
  2. they do not take into account ensuring that the mineral and nutrient intake of a low carbohydrate group is as high as that of a high carbohydrate group
  3. they feed the low carbohydrate subjects a higher protein diet, which can increase production of acidic compounds that could actually harm exercise performance.

One researcher named Steven Phinney has studied small groups of bicycle racers performing at a brisk bicycling pace (22-24 mph) for several hours. Unlike most bike racers in low carbohydrate studies, these bicyclists were allowed ample time to adapt to a diet of about 15% protein and over 80% fat, with the only carbs coming from the small amount of carbohydrates naturally found in meat. These cyclists’ performance was not affected negatively by the presence of nearly zero carbohydrates in their diet – although their muscle carbohydrate stores were significantly reduced. This was primarily because their bodies had become accustomed to burning fats as a fuel during exercise.

When You Need Carbohydrates

So when do you need carbohydrates for exercise and how should you get them? Here are 4 tips:

1. Don’t Eat Carbohydrates Before Moderate Cardio Workouts

During long cardio workouts, your body is actually very efficient at using fats as a fuel, especially when your intensity is not high. To put things in perspective, a champion marathoner running the Boston marathon is running at an intensity that would necessitate frequent carbohydrate feedings during that long workout. But an easy 90-minute morning jog does not require carbohydrates. You can simply roll out of bed and start running (I personally do this quite frequently). The first couple of weeks will be somewhat unpleasant as you grow accustomed to relying on fats as a fuel, and for that reason you can wean yourself off of long workout carbohydrates by having something like a sports gel about halfway through, but ultimately you won’t really need the carb load.

2. Eat Carbohydrates Before Hard Cardio Workouts

During hard cardio workouts, your body’s sugar needs are elevated and the muscles rely more on fast-burning carbohydrates as a fuel. But it is important to understand that you really do need to be exercising at a high intensity. When I ran an exercise physiology lab in which we measured carbohydrate utilization during exercise, people were usually running up a very steep treadmill incline at about 85-90% intensity before their bodies were burning primarily carbohydrates as a fuel. If you’re simply getting a little muscle burn or exercising under an 8 on a 1-10 scale during exercise, you don’t need dietary carbohydrates during a cardio workout. If you are actually at that high intensity, then you’re probably working out too hard to eat, in which case you can simply consume an easily digesting carbohydrate before you begin your workout. Fruit, potatoes, sports drinks or energy bars would all do the trick, and are generally best consumed 30 minutes to 2 hours prior to your hard workout (the bigger meal, the longer the time you’ll want to allow for digestion).

3. Eat Carbohydrates Before or During Hard Weight Training Workouts

An easy or short weight training circuit at the gym doesn’t really need to be fueled by dietary carbohydrates, especially when you bear in mind that your body naturally carries about 1,500-2,000 calories of storage carbohydrates that it can burn through, and it usually takes 1-2 hours of weight training to deplete this.

4. Eat Carbohydrates Before or During High Calorie-Burning Activities That Require Extreme Focus

Due to the tryptophan-serotonin connection, and also due to the fact that low blood sugars can potentially decrease focus and intensity, you shouldn’t venture fasted or only fed on fats and proteins if you’re about to embark on something like a high intensity 2-hour tennis match. While 18 rounds of golf or even a game of baseball can be fueled on fats and proteins, if you’re both trying to focus and simultaneously burn a high number of carbohydrates, you should eat 2 hours before the event, and then consume 100-300 calories of carbohydrates during the event (and during a long, grueling focused event like Ironman, I personally eat 350-450 calories of pure sugar from sports gels for up to 10 hours!).

Ultimately, carbohydrates have their time and their place, but if you find yourself constantly relying on carbs to get you through every workout, you’re probably not doing your body any favours when it comes to becoming more efficient at fat-burning.

Screen Shot 2016-01-17 at 3.07.25 PM



Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s