“Nothing in the world is more dangerous than sincere ignorance and consciencious stupidity.”
Martin Luther King Jr.
Recently, two ‘exercise physiologists’, Wendy Repovich and Janet Peterson, presenting at the American College of Sports Medicine (ACSM) 11th-annual Health & Fitness Summit & Exposition supposedly debunked “Top 10 Nutrition Myths.” Some of their statements were utter nonsense, so I decided to debunk their debunking. Fasten your seatbelts… here we go.
“Endurance athletes need to take in carbohydrates immediately after a workout to replace glycogen stores, and a small amount of protein with the drink enhances the effect. Drinking low-fat chocolate milk or a carbohydrate drink, like Gatorade, is better for the body, as they replace glycogen stores lost during exercise. Protein is not going to help build muscle, so strength athletes do not need to eat immediately following their workout.”
How moronic is that last statement anyway? Its well-established that one will remain in protein catabolic state when only carbohydrates are ingested after resistance exercise, so traditional sports drinks like Gatorade® are absolutely useless in terms of post-exercise muscle anabolism. In sharp contrast, amino acid ingestion alone significantly increases muscle protein anabolism after resistance exercise. However, consumption of both amino acids and carbohydrate results in much greater effects on muscle protein anabolism, suggesting an interactive effect between insulin, amino acid availability and resistance exercise (1).
It appears that these ‘exercise physiologists’ don’t even read ACSM´s own scientific journal Medicine & Science in Sports & Exercise. You see, a paper published in that ACSM journal few months ago also clearly demonstrated the importance of post-resistance exercise protein intake (2). Simply put, providing nutrition after exercise takes advantage of the anabolic signaling pathways that physical activity has initiated by providing amino acids and energy for protein anabolism (3).
Carbs and Fat Loss
“Cutting carbs from your diet may have short-term weight loss benefits due to water loss from a decrease in carbohydrate stores, but eating carbs in moderation does not directly lead to weight gain. The body uses carbs for energy, and going too long without them can cause lethargy.”
It is true that the rapid initial weight loss during a low-carb diet is largely due to the greater water loss. However, a number of studies have showed that carbohydrate restriction promotes fat loss too. In fact, a recent paper, published in the American Journal of Clinical Nutrition, demonstrated that low-carbohydrate diets favorably affect body mass and composition independent of energy intake (4). The suggestion that going “too long” without carbohydrates can cause lethargy is clearly fallacious. In reality, it is other way around; the human body will gradually adapt to a low-carb intake (i.e., keto-adaptation) (5). There are no studies that examine the optimum length of this adaptation period, but it is certainly longer than one week and likely more than 4 weeks. Thus, the short-term studies examining the effects of carbohydrate intake on exercise performance are biologically nonsensical.
Glycemic Index and Type II Diabetes
“High levels of glucose are not what “cause” diabetes [type II]; the disease is caused by the body’s resistance to insulin. Foods high on the glycemic index can cause glucose levels to spike, but this is just an indicator of the presence of diabetes, not the root cause.”
Oh my… and these ladies are physiologists? Do those individuals who have insulin resistance just wake up one morning and discover they somehow developed it in their sleep? Well, it is now clear that chronically high insulin levels down regulate the synthesis of insulin receptors, and fewer insulin receptors means insulin resistance. And what causes chronically high insulin levels? A diet rich in high glycemic carbohydrates. In addition, high-glycemic meals promote overeating6 and in turn body weight per se is a critical component for achieving healthy blood sugar levels.
Shortly after a high glycemic meal, blood insulin level rises higher than after a low glycemic meal with similar nutrients. Conversely, a high glycemic meal inhibits glucagon secretion (Glucagon has the opposite effect of insulin, i.e., it increases blood sugar). The strikingly increased insulin:glucagon ratio promotes uptake of various nutrients at liver, muscle, and fat tissue, and suppresses liver glucose output. Within some 60 minutes after a high glycemic meal, blood glucose begins to fall, often reaching levels below fasting, and release of storage fat from fat tissue is suppressed (6). It is the combination of rapidly declining blood glucose and low concentrations of fatty acids that stimulates overeating.
Traditional nutritionists have pretty much dismissed the whole glycemic index concept. They maintain that the glycemic index doesn’t apply in mixed meals and thus has no practical value. This isn’t the case, however. A recent literature review by Dr. Thomas Wolever discussed common misconceptions about the glycemic index (7). As pointed out by Wolver, the notion that the glycemic index doesn’t apply in mixed meals is based on flawed methodology. Recent studies show that nearly 90 percent of the variation in glycemic response of realistic mixed meals can be explained by differences in carb content and glycemic index. In other words, the glycemic index is for real. You should stick with the lower glycemic index foods but don’t become too obsessed. For example, you shouldn’t avoid cooked carrots because of their high glycemic index, so use common sense too!
“There are two kinds of fiber: soluble and insoluble. Insoluble fiber can cause problems in IBS [irritable bowel syndrome] sufferers; soluble fiber, however, is more easily absorbed by the body and helps prevent constipation for those with IBS.”
This topic is hardly relevant to gym rats. However, I wanted to include it because it so clearly demonstrates the ignorance of these ‘exercise physiologists’. Fiber, whether soluble or insoluble, is not absorbed by the body. Absorption refers to the movement of molecules across the gastrointestinal tract into the circulatory system, and we certainly don’t have a punch of fiber in our blood stream after a high-fiber meal. In fact, such a phenomenon would mess up the whole circulatory system. Rather, fiber shuffles on through the gastrointestinal tract until it gets to the colon where a very small amount is converted into short chain fatty acids (and absorbed as fat, not fiber) and the rest is moved on out with the stool. It isn’t rocket science, but then again, Repovich and Peterson obviously aren’t rocket scientists
Obviously, the indented audience of that ACSM presentation was goofs who have no clue about human nutrition and metabolism. Repovich and Peterson should spend more time trolling the scientific literature and less time debunking what they consider myths.
1. Manninen AH. Hyperinsulinaemia, hyperaminoacidaemia and post-exercise muscle anabolism: the search for the optimal recovery drink. Br J Sports Med. 2006 Nov;40(11):900-5.
2. Cribb PJ, Hayes A. Effects of supplement timing and resistance exercise on skeletal muscle hypertrophy. Med Sci Sports Exerc. 2006 Nov;38(11):1918-25.
3. Miller BF. Human muscle protein synthesis after physical activity and feeding. Exerc Sport Sci Rev. 2007 Apr;35(2):50-5.
4. Krieger JW et al. Effects of variation in protein and carbohydrate intake on body mass and composition during energy restriction: a meta-regression.
Am J Clin Nutr. 2006 Feb;83(2):260-74.
5. Phinney SD. Ketogenic diets and physical performance. Nutr Metab (Lond). 2004 Aug 17;1(1):2.
6. Ludvig DS. Clinical update: the low-glycaemic-index diet. Lancet. 2007 Mar 17;369(9565):890-2.
7. Wolever TM. Physiological mechanisms and observed health impacts related to the glycaemic index: some observations. Int J Obes (Lond). 2006 Dec;30 Suppl 3:S72-8.