Tuesday, February 28, 2012

High-fat versus low fat diets for endurance training and exercise performance

 Assignment for class:

I found the section in our book labeled "High-fat versus low fat diets for endurance training and exercise performance" interesting.  Supporters of the high-fat diet for endurance athletes say that an increase in fat intake overtime will encourage the burning of lipids by increasing the capacity mobilize and breakdown fat (1).  In a study done on two groups of males who had the same fitness status, one group was fed a high-carbohydrate diet (65% calories from carbs), and the other group was fed a high-fat diet (62% of total calories from fat).  Both groups exercised 3 days a week at 50-85% of their VO2max (aerobic capacity), for 60-70 minutes during the first 3 weeks, and 4 days a week during the last few weeks.  What the study found was that there was an increase in endurance capacity for those who consumed the high-fat diet (115%), however, the high-carbohydrate group was able to increase their endurance substantially (194%) (1).

Also, our book states that, "Comprised training capacity and symptoms of lethargy, increased fatigue, and higher ratings of perceived exertion usually accompany exercise when subsisting on a high-fat diet" (1).  It is important to remember that there negative health hazards associated with a high-fat diet.  What I found interesting, though, was that this risk may not be a hazard for athletes who burn a ton of calories each day (like endurance athletes), and consume a higher-fat diet (around 50% calories from fat, not the 62% like in the study).  This will NOT increase the risk for heart disease or elevated cholesterol levels, if the athlete maintains a healthy or stable body weight and is able to burn many calories each day (1).

Also, our book states that, "Conversely, significant restriction of dietary fat intake below recommended levels also impairs endurance performance" (1).  So, I think it's very important that athletes recognize this, especially if they are burning a lot of calories each day through training.  They NEED fat, and cannot limit it to dangerously low levels because they will NOT be able to give 100% in each workout or race.  They are still going to have great numbers for blood lipid profiles, triglycerides, etc., as long as they're burning enough calories each day.  I think it's out job to help people understand this.  There is so much junk out there in the media!
1.  McArdle, W. D., Katch, F. I., & Katch, V. L.  (2009).  Sports and exercise nutrition.  (3rd ed.).
            Batimore, MD:  Lippincott Williams & Wilkins. 

Sunday, February 12, 2012

The Negative Effects of a Low-Carb Diet.

I received a perfect score on this paper in Sports Nutrition, so I guess that means it's legitimate?  I don't fool people on health advice and always try to get the truth out to you :)  I really want people to know the truth.  There's a lot of crap out there.
     There are many diets in the diet industry that focus on low carbohydrate intake along with higher intakes of protein and fat.  According to what I have learned through science and the nutrition classes I have taken, the human body needs carbohydrates for it to function normally.  Also, eating higher than average intakes of protein and fat can have potential negative effects on the body (Tapper-Gardzina, Cotugna, & Vickery, 2002).  While searching for articles for this assignment that included misinformation on nutrition, I came across an article from Bodybuilding.com where people wanted to decrease carbohydrate intake to lose weight, but increase energy levels.  This did not make any sense to me, nor have any low-carbohydrate diets that I have read about in the past.  As an endurance athlete, I know how very important carbohydrates are in the diet, particularly complex carbohydrates.  However, just because the endurance athlete population needs carbohydrates to fuel their workouts, this does not mean that sedentary people or people who just strength train do not need carbohydrates for energy.  It does not make sense to eat hardly any carbohydrates in order to lose weight, when they are one of the macronutrients that systems of the body need to function correctly. 
            The article I found from Bodybuilding.com promotes a low-carbohydrate diet in order to lose weight and fat to make visible every muscle on the human body.  The name of the article is titled, “How Can I Increase Energy While Depleting my Carbs?” (Obadike, 2011).  The article states that in order to keep energy levels high, an individual must increase their fat and protein intake.  However, a scientific journal, The Nurse Practitioner, posted an article that states that this type of diet, a high-protein intake with low-carbohydrate consumption worries scientists because all of these diets encourage higher than normal values for protein.  They forbid followers to avoid foods containing higher amounts of carbohydrates (Tapper-Gardzina, Cotugna, & Vickery, 2002).  The diet from Bodybuilding.com wants the individual trying to lose weight to only eat carbohydrates around the time they are going to exercise, because if they eat carbohydrates anytime else during the day, they will store this nutrient as fat and not burn off the additional energy (Obadike, 2011).  Furthermore, since this diet wants their dieters to take in a low amount of carbohydrates when they are not exercising, they are just eating protein and fat the rest of the day (Obadike, 2011).  In my opinion, this will lead to boredom and cravings for carbohydrates because depending on how much activity level is performed, the body will favor carbohydrates.  “Carboydrate is the body’s preferred source of energy, and the body will revert to gluconeogenesis when carbohydrate intake is limited” (Tapper-Gardzina, Cotugna, & Vickery, 2002).  In the end, this diet will probably fail and followers will gain all the weight they lost back from reducing their carbohydrate intake.
            One more point this article made that I did not approve of was the fact that it was telling the dieters to reduce their aerobic exercise in order to conserve energy.  “You also may want to minimize your weekly cardio when depleting carbs in order to save the minimal energy you do have” (Obadike, 2011).  This is not going to work because it is proven that carbohydrates and aerobic exercise both increase energy levels (Tapper-Gardzina, Cotugna, & Vickery, 2002).  However, the article says that adding in more protein and fat will increase energy levels.  “Increase your protein and fat intake by 10 to 15 percent.  This will help give you more energy during your carb-depletion days.  Reduce your daily cardio to help you conserve energy.  Rotate your carbs intake to coincide with your highest physical activity level, which is probably your daily workout” (Obadike, 2011).  Lastly, the article claims that if people closely adhere to these rules, they will have more energy than anticipated while minimizing carbohydrates (Obadike, 2011).
            Just like any diet, though, this low-carbohydrate, high-protein diet will be unsuccessful.  “Researchers have estimated that 80% to 85% of dieters who lose weight will gain it back within 1 to 5 years.  Diets may fail because they restrict both the type and quantity of food, or require dieters to purchase special food” (Tapper-Gardzina, Cotugna, & Vickery, 2002).  These types of diets say that hunger is diminished since calories from fat and protein are not taken into account and dieters can eat as much food containing these nutrients as they want, as long as they are limiting carbohydrates (Tapper-Gardzina, Cotugna, & Vickery, 2002).  This puts the body into starvation mode.  According to the United States Department of Agriculture’s Dietary Guidelines and the Food Guide Pyramid, 275 grams of carbohydrate need to be eaten in a 2000 kcal diet.  In contrast, only 20 to 90 grams of carbohydrate are recommended in the usual low-carbohydrate, high-protein diet.  This is almost like putting the body in a state of starvation because glucose concentrations are decreased from low-carbohydrate consumption, which results in a condition called ketosis.  This circumstance is where the body uses energy from ketosis instead of carbohydrates by making ketones from fatty acids.  Ketosis can cause muscle breakdown,  producing more ketones if protein intake is very high (Tapper-Gardzina, Cotugna, & Vickery, 2002). 
            There is a lot of information from popular sources that say Americans consume too much sugar, which is what these high-protein, low-carbohydrate diets declare.  However, of total calories consumed, Americans closely met the proposed amount of keeping sugar consumption under ten percent (Tapper-Gardzina, Cotugna, & Vickery, 2002).  It is not really the carbohydrate consumption that is making America fat, but the amount of fat intake which leads to obesity.  “Researchers have shown a direct relationship between fat intake and obesity” (Tapper-Gardzina, Cotugna, & Vickery, 2002).  Interestingly, insulin resistance is brought on by old age, a sedentary lifestyle, obesity, high cholesterol, high-fat diets, and impaired glucose tolerance, not a greater intake of carbohydrates, which is what most of these high-protein, low-carbohydrate diets claim (Tapper-Gardzina, Cotugna, & Vickery, 2002).  Furthermore, studies have shown that an elevated consumption of saturated fat can cause insulin resistance, and a high ratio of omega-6 to omega-3 fatty acids will cause an increase in body weight along with increased fasting insulin levels in people with normal blood sugar (Storlien, Baur, Kriketos et. al., 1996).   It seems that every macronutrient and type of food in moderation will help individuals keep a healthy body weight.  “Weight loss from any type of diet will improve insulin sensitivity.  Although calorie restriction and exercise can increase weight loss, changes in macronutrient balance don’t appear to influence insulin action or promote weight loss” (Tapper-Gardzina, Cotugna, & Vickery, 2002).  The total amount of calories consumed, and not limiting certain macronutrients, is very important when one is trying to lose weight.    
            Some negative factors of the high-protein and fat, low-carbohydrate diet include elevated low-density lipoprotein and total cholesterol, which will increase one’s risk of developing coronary artery disease.  Also, other chronic illnesses and cancers can develop from eating a high fat diet (Tapper-Gardzina, Cotugna, & Vickery, 2002).  One study that looked at a high-protein diet over a year used ten individuals to show that low-density lipoprotein, very low-density lipoprotein, total cholesterol, high-density lipoprotein, fibrinogen, and triglyceride profiles all became worse.  Also, C-reactive protein was elevated, which leads to more inflammation in the body (Fleming, 2000).  Additionally, when consuming a high-protein diet, as much as fifty percent of calcium is lost in the urine, which may predispose individuals to developing osteoporosis earlier (Tapper-Garlick, Nurlan, & Patlak, 1999).  Elevated calcium losses in the urine can cause bone resportion, along with no bone formation (Kerstetter, Mitnick, Gundberg et. al., 1999).  In a study done on teenagers who were on a high-protein, low-carbohydrate diet to promote weight loss over the course of three months, researchers found that even while taking supplements for calcium and vitamin D, bone mineral density was drastically reduced.  However, when these individuals returned to eating a normal amount of carbohydrates, they did not excrete a significant amount of calcium in the urine (Willi, Oexmann, Wright et. al., 1998). 
            While on a high-protein, high-fat, low-carboyhydrate diet, most of the weight loss is due to water, not fat.  “Diuresis, caused by low-carbohydrate intake and its effects on sodium loss, water loss, and glycogen depletion, is the primary reason for initial rapid weight loss on the LC-HP diet.  Severely restricting carbohydrate also suppresses appetite, likely due to nausea from sodium loss” (Tapper-Gardzina, Cotugna, & Vickery, 2002).  Also, the LC-HP (low-carbohydrate, high-protein) diet does not contain enough fiber.  Fiber is shown to reduce total and low-density lipoprotein, along with regulating the digestive system.  Fiber decreases the risk of some cancers, diabetes, stroke, obesity, and diverticular disease (Tapper-Gardzina, Cotugna, & Vickery, 2002).  “Researchers believe that the soluble fiber found in fruits and vegetables, oat bran, and legumes, interferes with the absorption of bile acids, thereby lowering cholesterol levels in the blood and reducing the risk of myocardial infarction.  Fiber also lowers insulin secretion after a meal by slowing nutrient absorption” (Tapper-Gardzina, Cotugna, & Vickery, 2002). 
            When individuals seeking to lose weight try a low-carbohydrate, high-fat and protein diet, they are missing certain nutrients they need in their diet to function properly, such as vitamins, minerals, and fiber.  Eating these three essential nutrients will aid in warding off diseases of all kinds (Tapper-Gardzina, Cotugna, & Vickery, 2002).  Also, it is very important to eat every food in moderation, and when trying to lose weight, eat 300 to 500 calories less per day, as well as exercise regularly.  The amount of aerobic exercise an individual takes part in can also help protect the body against chronic diseases, while lowing cholesterol, triglycerides, resting heart rate and blood pressure, as well as improving sleep patterns and energy levels (Cooper, 2010). 

Cooper, K.  (2010).  The benefits of exercise in promoting long and healthy lives-my
            observation.  Methodist DeBakey Cardiovascular Journal, 4, 10-12.
Fleming, R. M.  (2000).  The effect of high-protein diets on coronary blood flow.  Angiology,
            51, 817-826.
Garlick, P. J., Nurlan, M. A., & Patlak, C. S.  (1999).  Adaptation of protein metabolism in
            relation to limits to high dietary protein intake.  European Journal of Clinical Nutrtition,
            53, S34-S43. 
Kerstetter, J. E., Mitnick, M. E., Gundberg, C. M. et. al.  (1999).  Changes in bone turnover in
            young women consuming different levels of dietary protein.  Journal of Clinical
            Endocrinology & Metabolism, 84, 1052-1055. 
Obi, Obadike.  (2011).  How can I increase energy while depleting my carbs?  Retrieved from
Storlien, L. H., Baur, L. A., Kriketos, A. D., et al.  (1996).  Dietary fats and insulin action.
            Diabetologia, 39, 621-631.
Tapper-Gardzina, Y., Cotugna, N., & Vickery, C. E.  (2002).  Should you recommend a low-
            carb, high-protein diet?  The Nurse Practitioner, 27, 52-59.
Willi, S. M., Oexmann, M. J., Wright, N. M. et. al.  (1998).  The effects of a high-protein,
            low-fat ketogenic diet on adolescents with morbid obesity:  Body composition, blood
            chemistries, and sleep abnormalities.  Pedriatrics, 101, 61-67.

Wednesday, February 8, 2012

Gender Differences in Carb/Fat use During Endurance Exercise...Females may have an Advantage..

I'm just going to quote my sports nutrition book here:

"Available data support the notion of gender differences in carbohydrate metabolism in exercise.  During submaximal (steady state) exercise at equivalent percentages of VO2max (or same relative workload), women derive a SMALLER proportion of total energy from carbohydrate metabolism than men.  This gender difference in substrate oxidation does not persist into recovery."  Interesting.  So, women rely more on fat than tap into their carb stores than men, which is why females may be able to run/bike/swim longer, in GENERAL, not everyone.  And, especially once you start getting into very long distances.

And looking into the physiology further..." With similar endurance-training protocols, both women and men show a decrease in glucose flux for a given submaximal power output.  But at the same relative workload after training, women display an exaggerated shift toward FAT catabolism (fat breakdown), whereas men do NOT.  This suggests that endurance training induces greater glycogen-sparing at a given relative submaximal exercise intensity for women than for men.  This gender difference in substrate metabolism's response to training may reflect differences in sympathetic nervous system adaptation to regular exercise (i.e. a more blunted cholamine response for women).  The sex hormones estrogen and progesterone may affect metabolic mixture indirectly via interactions with the catecholamines or directly by augmenting lipolysis (fat breakdown) or glycolysis (carb break down).  Five potential sites for endocrine regulation of a substrate (fat/carbs) use include:

1.  Substrate availability (via effects on nutrient storage)
2.  Substrate mobilization from body tissue stores
3.  Substrate uptake at tissue site of use
4.  Substrate uptake within tissue itself
5.  Substrate trafficking among storage, oxidation, recycling

Any glycogen-sparing metabolic adaptations to training could benefit a woman's performance during high-intensity endurance competition."

Wow, cool!  So, men are more powerful and stronger than women, but it seems women can last longer when it comes to endurance events, especially ultra's.  I have been searching around for research to back up that theory I have been reading about over the course of 2 years. 

From the book Sports and Exercise Nutrition by William D. McArdle, Frank L. Katch, and Victor L. Katch.