What’s in your Bottle: Part 2: Sugar Burner or Fat Burner?

Your body prefers either fat or sugar as a primary endurance fuel

No matter if you’re a sugar burner or a fat burner for endurance, we all need sugars as “rocket fuel” for performance racing. Only a specific lab test will tell for certain which fuel your body prefers, but it is modifiable to a point. The point of view of the author, both anecdotally and after much research, as that fat burners have the edge.

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  • You should be training like you intend to race; that counts for nutrition, too
  • Are you a “sugar burner” or a “fat burner?”
  • The length of the event, the intensity of the event, your fitness, and your weight are the factors that determine your race nutrition
  • You can’t process what you can’t tolerate
  • Without carbs, you bonk. Without water, well, it’s more dire than that.
  • During-event nutrition isn’t the only thing to think about: pre-event and post-event are critical considerations, too
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Your regular, day-to-day diet


is a strong indicator for you being either a “sugar burner” or a “fat burner.” Both will fuel according to identical guidelines immediately before and after races and workouts, but the endurance ramifications of each diet are significant. Also, your type factors strongly in terms of weight management.

In short…for intense races and workouts, both types need high glycemic carbohydrates before, during, and after in order to perform at their best. But for long, moderate events (such as long weekend base mile rides) the sugar burner will need to be much more conscious of their sugar intake than the fat burner. The reason for this is that sugar burners can’t afford to run low, unlike fat burners, whose metabolisms are set to convert fat to fuel.

Sugar burners can find it difficult to eat enough carbs during long efforts. Their bodies are burning it faster than their gut can process it from any source: sports drinks, gels, bars, etc. As they continue to gulp and chew, they fill up, and eventually, are forced to quit.

Most Americans eat a diet that is rampant in simple sugars, as opposed to healthy, low-glycemic, carbohydrate-dense energy sources such as:

  • sweet potatoes
  • parsnips
  • onions
  • beets
  • carrots
  • butternut squash
  • pumpkin

These sources are the gold-standard go-to’s for fat burners.

[callout icon=”hb-moon-bike”]The myths of “calories in, calories out,” “eat a calorie, burn a calorie,” and “since I’m exercising so hard, I can eat whatever I want” are alive and well in even the most serious racers of virtually any level.[/callout]

I can hear you now: “Where are the whole grains? Those are healthy sources of carbs, right? Shouldn’t they be a primary source of carbohydrate?”

In a word, no. They are not nutrient dense. Since they are nutrient weak, you eat significant amounts if you’re relying on them as a primary energy source. Since they are carbs, and since you would require a significant amount, your blood sugar will rise enough for your pancreas to need to kick in to overdrive as a result. I don’t believe grains should be a significant part of a cyclist’s diet, especially if they already eat a significant amount of nutrient-weak carbohydrates and sugars.

Unfortunately the simple-sugar crowd includes most American cyclists! The myths of “calories in, calories out,” “eat a calorie, burn a calorie,” and “since I’m exercising so hard, I can eat whatever I want” are alive and well in even the most serious racers of virtually any level. These “sugar burners” are eating diets remarkably high in simple sugars and simple carbohydrates and as such, have not trained their bodies to be able to tap into fat stores for energy when their glycogen stores are running low. On the contrary, they are actually generating so much insulin, that the glucose they’re eating has no choice but to be stored away as fat. They also run the very significant risk of insulin resistance. This is the result of cell inflammation caused by exposure to so much insulin necessitated by the flood of glucose in their bodies.

Insulin resistance is the precursor to type 2 diabetes, by the way.

“But I’m slender, am a cyclist, and enjoy soda, donuts, cereals, and other simple sugars.”

I was the same way, until I visited a nutritionist and realized I was just like one of the many patients Dr. James Bell studied. I was one of the “thin outside, fat inside” types. My body fat percentage, despite hard training, was 19%. That’s way high for a competitive cyclist, despite my 6-foot, 155 pound frame. After changing my diet, virtually eliminating grains, simple sugars, and dairy, my body fat normally fluctuates between 7 – 9%. Oh, and I’ve lost 10 pounds.

Needless to say, this fat burner climbs faster than when he was a sugar burner!

“Fat burners,” on the other hand, eat primarily meats, vegetables, healthy fats, and whole fruits. They avoid or eliminate most simple sugars, and therefore have metabolisms that don’t need to endure the ravages of insulin spikes, which include feeling hungry a lot of the time, coupled with drowsiness after meals. They convert the simple sugars used during workouts and events more easily, and their bodies will more easily convert stored fat as fuel. The glycogen stores in their livers and muscles are well-topped. In short, they’ll go longer before they have to be conscious of staving off the dreaded “bonk.” In fact, a fat burner can easily do hard workouts of up to 75 minutes on water alone.

If you’re regularly consuming simple sugars day-to-day, then you’ll need more vigilance to insure that your glycogen stores remain full prior to your hard events, and throughout the event. In other words, you need to stay topped off as you burn through the glycogen stores in your muscles and liver. A carb-rich sport drink plus some carb solids in your jersey pocket will be required more frequently than what a fat burner will require, because you’ll not be able to convert stored fat to energy quickly enough to be of benefit on a hard ride.

If you’re a sugar burner, it’s worth exploring a dietary change that can help your body rely less on a constant flow of high glycemic carbs when you’re not in a high intensity race situation.

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Question: Are you a “sugar burner” or a “fat burner?” How do you see this affecting your event nutrition needs?

Sam Lowe

I've been a road cyclist with a penchant for speed ever since my first-ever paycheck holiday. I blew the whole wad on a turquoise Schwinn Tempo with then-new Shimano 105 indexed shifting way back in 1985. I've been a voracious consumer of racing-oriented information ever since. Training, nutrition, bike fit, racing techniques, and all manner of "kit." Between nearly 30 years of riding, racing, and reading about racing, I'm ready to help you get ready to race.

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