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Why Carbs are Bad — and Good

By Katie Davis 

Low-carbohydrate diets are all the craze. On a weekly basis, athletes are telling me they limit their carbohydrate intake because "carbs are bad". I should really create company shirts that say "I [heart] Carbs" (similar to those I [heart] NY shirts). It is a shame that carbohydrates get such a bad rap. However, it is an even bigger shame that often athletes don't really know what these nutrients are for, in what foods they are found or why cutting them is a good or bad idea. 

carbWhat they do
Carbohydrate (or sugar) is a source of quick energy for your body. When not slowed down by fiber, fat or protein, pure carbohydrate can be absorbed into your system and utilized for energy very quickly (15-20 minutes). This is why the calories in sports drinks, gels, chews, etc., are 100 percent from carbohydrate. The point of these products is for them to get out of your stomach quickly and to your muscles where you can actually utilize them. The interesting thing about an exercising muscle is that the higher the intensity of the workout, the more it relies on carbohydrate for energy. 

When there is not enough oxygen available (called an anaerobic state), the body can only run metabolic processes that utilize carbohydrate as the fuel. You can imagine that this can mean huge detriments to someone who cuts carbs and then performs an intense workout. No carb = no fuel = poor performance = muscle breakdown as the body struggles to use muscle protein for energy. And you want to know a secret? The body really doesn't recognize the difference when it comes to the source of that sugar. Whether it is from whole food, pure sugar, honey, high fructose corn syrup, agave nectar… the body doesn't know and really doesn't care. Sugar is sugar and that's what it needs during exercise. 

Where you find them
Food sources like grains include carbs, such as breads, cereal, pasta, rice, oatmeal, popcorn, pancakes, waffles and crackers. Carbohydrate is also found in fruits (fresh, juice, dried), vegetables and dairy products. There are higher amounts in starchy items such as baked beans, corn, potatoes, legumes and peas. Carbohydrate is not found in meat, fish, or nuts/oils. Of course many diets also include added sugars: honey, white sugar, brown sugar, agave nectar, corn syrup or high fructose corn syrup.

What makes a carbohydrate source more or less "healthy" is what it contains in addition to the sugar: vitamins, minerals, water, fiber, whole grains, protein, poly- and mono-unsaturated fats. Pure sources of sugar (added sugars) raise blood sugar very quickly, while foods with added fiber, whole grain, protein or fat create a gradual increase in blood sugar, which is better for overall long-term health. It is not really the source of sugar that matters, it is what comes (or doesn't come) along with that sugar that makes the difference.
Here is a list of foods that each contain ~15gm of carbohydrate:
1 slice of bread
1/3 cup pasta/rice
3 cups popcorn
1/2 cup fruit juice
1 tennis-ball sized piece of fresh fruit
1/2 cup starchy vegetables
1 cup non-starchy vegetables
1 cup milk 
4 teaspoons white or packed brown sugar
3 teaspoons high-fructose corn syrup, honey or agave nectar

Why limiting may be helpful
Limiting carbohydrates might be helpful when trying to lose weight — especially fat weight. During the "low-fat, no-fat" craze, people replaced fat with mainly carbohydrates, which has wreaked havoc on our health in the form of weight gain, high triglycerides, and Type-2 diabetes, to name a few. So, sometimes a limit is necessary, especially on added sugars whose calories add up fast. Personally I would rather have 3 cups of popcorn than only 3 teaspoons of honey.

When I say limit, this is a very relative term. Someone trying to lose weight should still be eating a minimum of 3gm carbohydrate per kilogram of body weight. That means an athlete who weighs 175 pounds should maintain an intake of ~240g of carbohydrate daily. Of course, an athlete trying to lose weight needs to be very careful to not limit carbohydrate intake when in peak/hard training time. This brings us to the next point:

Why limiting may not be helpful
Often athletes limit intake so much that performance is hindered. Remember that the exercising body loves and needs carbs. So, a carbohydrate intake too low for training needs will force the body to break down muscle for energy as well as potentially induce early fatigue, muscle cramping and increased risk of illness and injury.

Where is that line between too little and too much? This is where seeing a sports dietitian is important. A sports dietitian can evaluate your current training regimen, daily food intake and training/competition goals to assure you get just enough — but not too much — carbohydrate. In my experience, most athletes lean toward not enough carbohydrate; when this is corrected many feel much better both during and after training.

kateKatie Davis MS, RD, CSSD, LDN has a mission to help ordinary athletes become extraordinary competitors by using whole-food based nutrition to improve athletic performance. She is the owner of RDKate Sports Nutrition Consulting, based out of Naperville, where she offers expertise in sports nutrition, eating disorders/disordered eating, intuitive eating and weight management for sport. Katie holds a Masters Degree in Nutrition with an emphasis in Exercise Physiology. She is both a registered dietitian (RD) and 1 of only 550 RDs in the United States to be board -certified as a specialist in sports dietetics. As a runner, triathlete, snowboarder, and rock climber, Katie understands the physical and mental challenges of being a top athlete. Katie has previously consulted with NCAA Division I & Division III, NFL and NBA athletes; she truly brings both her knowledge and experience to the table as sports dietitian. Katie is available for individual consulting, team talks and group seminars. Visit her website at; from there you can navigate to her weekly blog, Eat to Compete, and connect with her on Twitter or Facebook. Contact her directly at