My Carbohydrate Rebuttal

This is my response to a comment from a reader about my carbohydrate blog entry...

Thank you for reading and commenting on my blog, I truly appreciate it!

I agree with you that a high carbohydrate diet is not for everyone. Perhaps, I came off that way, but in my personal opinion a BALANCE of ALL macronutrients; carbohydrate, protein and fat, as well as total calorie intake are extremely important for athletes. Fat and protein should not be omitted from an athletes diet! Nor should carbohydrate!

YES, there has been some recent research studies examining high-fat diets and ENDURANCE athletes. The results of many of these studies have been intriguing and interesting.

Any information that I post on my blog, I want it to be scientific and evidence-based. I often turn to the American Dietetic Association (ADA) for scientific, evidence-based information. And so...

The 2009 Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance states the following:

"Approximately 50% to 60% of energy during 1 to 4 hours of continuous exercise at 70% of maximal oxygen capacity is derived from carbohydrates and the rest from free fatty acid oxidation (3). A greater proportion of energy comes from oxidation of free fatty acids, primarily those from muscle triglycerides as intensity of the exercise decreases (3). Training does not alter the total amount of energy expended but rather the proportion of energy derived from carbohydrates and fat (3). As a result of aerobic training, the energy derived from fat increases and from carbohydrate decreases. A trained individual uses a greater percentage of fat than an untrained person does at the same workload (2). Long-chain fatty acids derived from stored muscle triglycerides are the preferred fuel for aerobic exercise for individuals involved in mild- to moderate-intensity exercise (4)."

So, yes, a "trained" endurance athlete can use energy derived from fat sources, sparing energy from glycogen stores. Again, it is amazing how our bodies can adapt. I did know that endurance athletes use carbohydrate and fat as a fuel source, I don't know if I mentioned it in this entry, but I may have in the protein entry, because a small amount of protein is also used for energy for endurance athletes.

Yet, the ADA, Dietitians of Canada, and the ACSM go on in this position paper to recommend the following:

"The Acceptable Macronutirent Distribution Range for fat is 20% to 35% of energy intake (17). The 2005 Dietary Guidelines (16) and Eating Well with Canada's Food Guide (28) make recommendations that the proportion of energy from fatty acids be 19% saturated, 10% polyunsaturated, and 10% monounsaturated and include sources of essential fatty acids. ATHLETES should follow these general recommendations."

"Consuming < or equal to 20% of energy from fat does NOT benefit performance. Fat, which is a source of energy, fat- soluble vitamins, and essential fatty acids, is important in the diets of athletes. High-fat diets are not recommended for athletes."

"Carbohydrate recommendation for athletes range from 6 to 10g/kg body weight per day. Carbohydrates maintain blood glucose levels during exercise and replace muscle glycogen. The amount required depends upon the athlete's total daily energy expenditure, type of sport, sex, and environmental conditions."

The protein recommendations are similar to the ones I mention in my protein blog entry.

In my personal opinion and based on the position of the ADA, Dietitians of Canada, and the ACSM, I feel that more research needs to be conducted before recommending a high-fat diet. I think that fat is essential and important for an athletes' diet, as well as carbohydrate and protein. I don't think that any athlete should follow a non-fat or low-fat diet.

If you want to extract information out of running books, Runner's World, "The Runner's Body" (2009) by Ross Tucker, PhD, and Jonathan Dugas, PhD, also discuss fuel sources, both carbohydrate and fat. These authors also discuss how the well trained long-distance runner can adapt to use more fat as a source of fuel, sparing glycogen stores. They state, "the scientific research on high-fat diets and fat-loading is still equivocal." They go on to explain how some research has "found that fat-loading actually improved performance during endurance exercise (p. 144)." They also explain how there is evidence of individual variation, meaning a high-fat diet may help some athletes, but may impair other athletes' performances. They conclude, "given our lack of understanding of the interindividual responses to high levels of fat intake, the prudent approach, for now is to focus on a high carbohydrate diet and make sure that you are not compromising performance by depleting your glycogen stores before exercise... for the average runner engaging in marathons and shorter races, adapting to a high-fat diet is unlikely to yield significant benefits (p.144-145)."

Finally, as to the reasons I explained in my carbohydrate blog entry, carbohydrates are important to athletes as a source of energy, as are fats and protein! No athlete should follow a fat-free or low-fat diet!