Carbs and Fats on Rides




Spring is beautiful in Colorado! The hills are green from the early spring snowfalls and the lakes are full from runoff from the mountain snowpack. Last week I rode up to Carter Lake and back, a 3:30 jaunt that included exploring a dirt road variation. I seek out dirt roads because they are safer with much less traffic and more scenic, although the riding is harder and slower.

At the lake I kicked back at the marina, drank a Coke (not diet), ate a half-dozen fig bars and soaked in the sun and the beauty. On the way I’d eaten a banana, apple slices, a granola bar and drank a bottle of tea sweetened with white sugar, and a bottle of water. Pedaling home — it always seems farther than riding out — I drank a bottle of sports drink, another bottle of water and ate a couple more granola bars. Over the course of the 3:30 ride I ate almost all carbs.

Avoiding the Sugar Rush and Crash

Conventional wisdom is that if you eat sugary food you’ll get a sugar rush and then your blood sugar will crash and your energy will wane. I consumed a lot of sugar: the Coke and sports drink were loaded with sugar, and the cookies were 50% sugar. The granola bars were less: 25% sugar. Why didn’t I have that sugar rush and crash? Three reasons:

1. I kept eating and drinking sweets. My blood sugar didn’t crash because I kept feeding it a steady supply of sugar.
2. I consumed a mix of sugary stuff combined with starches and fat.
3. What I consumed had a moderate glycemic index.

What is the Glycemic Index (GI)?

GI measures how fast a food causes your blood glucose to rise. White bread with a GI of 100 is at the top of the scale against which the GI of other foods is measured. Glucose also has a GI of 100.

  • High GI 70-100

  • Moderate GI 40-70

  • Low GI <40 li="">

Table sugar, which is glucose and fructose, has a GI of only 65, so my sweetened tea had a moderate GI, as did the Coke with a GI of 63. The sports drink had a high GI of 83, and the newtons and breakfast bars had GIs in the 70s. The apple and banana had GIs in the 40s.

In general, you should eat low- to moderate-GI foods before a ride, and moderate- to high-GI foods during a ride. During a race the pros eat primarily carbohydrates with a high glycemic index for instant energy. You can eat tactically: moderate GI foods during much of the ride and then a high GI food for quick energy on a climb.

There is an explanation of GI with a comprehensive database of the GIs of different foods here.

Why Eating Carbs Is Important

When you exercise your muscles are burning a combination of fat and glucose, and the harder you exercise the higher the proportion that comes from glucose. Your body stores the glucose as glycogen, and your body can store only enough glycogen for 60 – 90 minutes of hard exercise, or two to three hours of moderate riding. Your brain can only burn sugar (glucose) for fuel, and when you run out of glucose, you bonk. Your body metabolizes all carbs into glucose, a sugar. This is another reason why eating sugar isn’t bad – your body’s going to turn carbs into sugar anyhow.

For more, see last week’s column on the Six Success Factors for Endurance Riders.

What are Carbs?

When we think of carbs we often think of bread, pasta, rice, potatoes and starches like that. Carbs also include fruits and vegetables, which are almost 100% carbs. Low-fat milk is 50% carbs and low-fat yogurt is 66% carbs. Legumes (kidney beans, chili beans, etc.) are 50 to 75% carbs. Breakfast cereals without added sugar (Corn Flakes, Grape Nuts) are 100% carbs.

Fruits, vegetables, dairy products and legumes all provide essential vitamins and minerals. Whole grain bread and pasta, brown rice and potatoes with their skins also have important vitamins. You can eat a healthy high-carb diet.

Is a Low-Carb, High-Fat Diet Bad?

Last week Dr. Gabe Mirkin wrote an excellent column on Low-Carbohydrate Diets Harm Athletic Performance. Several readers e-mailed me asking my thoughts — it depends on what you mean by “performance.” Dr. Mirkin explains correctly that a low-carb diet inhibits high-intensity training and performance. The 2016 Position Paper on Nutrition and Athletic Performance by the American College of Sports Medicine makes the same point: low-carbohydrate availability limits the ability to train hard and race hard. If “athletic performance” for you means hard club rides, intensity training or racing, then a low-carb diet is bad.

One e-mail was from a reader who does 200 to 1200K brevets and wondered if a low-carb diet was bad for him. When he’s riding, most of his energy is coming from fat, with a smaller proportion still coming from carbs. By training on a low-carb diet he can train his body to metabolize a higher proportion of fat during an endurance ride, thus sparing precious glycogen. Some ultra runners have switched to high-fat, low-carb diets. Because they burn primarily fat, they can run 100-mile races without having to eat frequently, thus reducing GI problems.

In March I wrote about the pros and cons of a High-Carb or High-Fat Diet.

Experiment of One

I've used this phrase numerous times, but it's worth repeating that we’re each an experiment of one. When I was riding a lot of brevets in the past, one of my friends ate a lot of burritos that he bought at mini-marts. Another friend ate and drank sports nutrition products. I ate fruit, cookies, breakfast bars, pretzels, etc,. that I could buy at mini-marts. We all finished multiple brevets, including Paris-Brest-Paris several times.

Experiment with different foods and drinks to find out what works for you. What provides a steady stream of energy, tastes good and doesn’t cause GI problems? Some riders like the simplicity of pre-packaged cycling food. Others prefer to eat "real" food like the cookies, pretzels and such I prefer. Same with hydration. Go with what works for YOU.

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