Posted: June 18, 2004
Multisport: How ‘Net Carbs’ Can Hurt Athletes
Written by: Ashley Kipp, CTS Expert Coach, USAC Cycling Expert Coach
Over the past several decades, American weight loss trends have shifted from low-fat, low-calorie, to the strict regimens of the “Grapefruit Diet” or the “Cabbage Diet,” to the current miracles of the “low-carb” diet. Recently, it seems like everything revolves around controlling carbohydrates, and athletes are getting caught up in the frenzy. What athletes often fail to realize is that low-carb diets were designed for significantly overweight, sedentary people; they were not designed to supply the nutrition active people need to support exercise and training. While small ‘net carb’ numbers are welcomed by low-carb fanatics, athletes should regard these same numbers as energy that’s been stolen from them.
Grocery store aisles are lined with low-carb snack bars, low-carb breads, and even low-carb catsup. Honestly, if someone is eating enough catsup to be worried about its overall contribution to their carbohydrate intake, there are probably some other eating habits that need to be addressed. Fast food chains have also embraced the fixation with bashing carbohydrates. Low-carb burgers without buns and low-carb sausage, egg, and cheese breakfast bowls fill television and billboard advertisements day after day. For most people, in an examination of the connection between extra body weight and frequent consumption of fast food hamburgers, it’s not the bun that’s the problem.
The claims that backers of the low-carb diet trend are taking are that sugar and refined carbohydrates (like bread, pasta, rice, and cereal) increase the body’s production of insulin and thus promote body fat storage. Further statements argue that the insulin “spike” caused by carbohydrates eventually causes “insulin disorders” which greatly increases the risk of obesity, coronary heart disease, and diabetes. Low-carb diets are based on the goal of eliminating the blood sugar “spikes” that supposedly lead to and cause insulin mediated storage of carbohydrates as body fat.
What Is a ‘Net Carb’ Anyway?
In an effort to reduce the amount of carbs that are reported on product package labels, manufacturers have come up with the term: ‘Net Carbs.’ What this refers to is the number of total carbohydrates in a serving size of a product, minus the fiber content of the food exceeding 5 grams per serving, and also minus the sugar alcohols that are said to have little or no effect on blood sugar. Because fiber is generally indigestible and sugar alcohols (hydrogenated chemicals designed to compensate for the bulk missing from the lack of carbohydrates in the product) are not absorbed very well, manufacturers do not report these numbers as “impact” or ‘net carbs.’ It would seem that the solution to weight loss is easy… consume food that is not digestible.
Where Do the Carbs Go?
The truth, though, about low-carb assertions, is much more complicated and entirely realistic. The term ‘net carbs’ is really just creative marketing terminology used to sell popular and pleasantly textured and flavored foods as “low-carb.” The FDA requires no testing or regulation of foods marketed with these terms and does not approve the expression. In fact, there are also dangers associated with some low-carb foods, due to the way manufacturers produce them. The artificial sweeteners and sugar alcohols that are used to replace the original carbohydrate content in the foods are not absorbed… so where do they go? If you consume more than 25-50 grams of sugar alcohols in a day, you’ll find out it goes right through you. Such products can have a significant laxative effect when eaten in excess, and need to have a laxative warning on the label. Sugar alcohols aren’t digested or absorbed in the small intestine, and are fermented in the large intestine, which can cause gastrointestinal distress and/or diarrhea. The carbohydrate goes right through you! The only truly “Low Carb” foods that have little to no sugar content are meats, nuts and seeds, some cheeses, and creams.
Furthermore, the initial and rapid weight loss (4-6 lbs.) that followers of low-carb diets experience is almost entirely from glycogen depletion and loss of water weight. Each gram of glycogen (or carbohydrate energy) in the body is stored with 3 grams of water. So, each gram of carbohydrate energy, then, accounts for 4 grams of body weight. By eliminating carbohydrates from the diet, the body is forced to burn through its stored glycogen. For a sedentary person, this may take up to two days; for an athlete, all it takes is a few hours. It is important to know, though, that the water weight lost during this time does not directly lead to dehydration. The water lost is from muscle tissues, not from other body tissues, organs, and blood volume.
What Does this Have to Do With Me?
Artificial sweeteners and sugar alcohols certainly have their place. They have allowed millions of diabetic Americans to enjoy an increased variety of foods. They have also allowed clinically obese people to drastically cut back on overall calorie consumption while still enjoying the satisfaction of good and sweet tasting food on a regular basis. However, for athletes, low-carb diets can be bad news.
Once glycogen stores are depleted, the body seeks out fat and protein sources for energy. First it turns to protein, converting amino acids from muscle tissue into glucose in the liver. This process is relatively slow and can really only produce enough carbohydrate to fuel your brain and nervous system. When no relief comes from ingested carbohydrate, you start producing ketone bodies (byproducts of fat metabolism) and releasing them into the bloodstream. As ketone levels increase, you enter a state of ketosis, which suppresses the appetite, but can also be accompanied by undesirable side effects, such as nausea, headaches, fatigue, and breath that smells like ammonia. Athletes on low-carb diets have difficulty sustaining even moderate intensity workouts of 50-65% of max heart rates when ketone levels are elevated.
Although low-carb diets and ‘net carb’ counting may have their place for some people in society, it is clear that these dietary practices are not appropriate for athletes. The routine and guidelines for maintaining the diet call for avoiding exactly what athletes need: digestible, usable, and absorbable carbohydrate that powers our muscles with energy. Carbohydrate is the most versatile type of energy. It feeds your brain and powers your muscles during both anaerobic and aerobic metabolism. Carbohydrate is the fuel that can be burned quickly, providing the power for acceleration and high performance.
Ashley Kipp is an elite coach and NASN Sports Nutritionist at Carmichael Training Systems and a certified Expert level cycling coach with USA Cycling. She possesses a strong background in athletic performance and has extensive experience in cycling, distance and endurance training. She can be reached at firstname.lastname@example.org.
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