On November 14th and 15th, 2008, dietitians, sports nutritionists, and other experts from around the globe gathered to hear each others’ current research in the area of sports and fitness nutrition. Sponsored by Nestlé Nutrition and PowerBar and led by Professor Asker Jeukendrup of the University of Birmingham, this two-day event brought insights and learning from international researchers. Here is a summary of the event and the thought leaders in sports nutrition.
1. Topic: Protein and Weight Loss
Presenter: Kevin D. Tipton
School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
Discussion:
Because athletes often engage in weight loss activities for aesthetic or performance improvements, the influence of macronutrients, in addition to energy intake, is important. A diet emphasizing protein has been evaluated as a weight loss tool as it may help improve satiety, preserve muscle mass, increase thermogenesis and perhaps increase fat oxidation.
Take home:
A diet high in protein may be desirable for some athletes under supervision and body composition analysis. If maintaining muscle mass is crucial, a high protein diet may be a viable option. Protein intake increases should be from low-fat dairy, lean meats and fish, oats and whole grains. Tipton suggests a carbohydrate to protein ratio of ~1.5 while consuming 80% of energy requirements and increased physical activity, especially strength training.
Select reading(s):
Layman DK and Walker DA. 2006. Potential importance of leucine in treatment of obesity and the metabolic syndrome. J Nutr 136: 319S–323S.
Paddon-Jones D, Westman E, Mattes RD, Wolfe RR, Astrup A and Westerterp-Plantenga M. 2008. Protein, weight management, and satiety. Am J Clin Nutr 87: 1558S–1561S.
2. Topic: Train Low — Compete High!
Presenter: Keith Baar
Division of Molecular Physiology, University of Dundee, Dundee, United Kingdom
Discussion:
Although glycogen loading has been known to increase endurance performance, this concept is being challenged as there may be benefits to training in a glycogen-depleted state. When glycogen-depleted, the athlete may adapt and utilize amino acids and increase fat oxidation. This may improve the ability to use fat as a fuel for the endurance athlete by increasing the enzymes participating in fat oxidation.
Take home:
Incorporating training days in a glycogen-depleted state into the athlete’s regimen may help to improve their ability to oxidize fat. This can be accomplished by exercising at 70% of maximum for 30 minutes to one hour without carbohydrate supplementation. Following this session or a fast, exercise for one to three hours and include high intensity work.
Select reading(s):
Narkar VA, Downes M, Yu RT, Embler E, Wang YX, Banayo E, Mihaylova MM, Nelson MC, Zou Y, Juguilon H, Kang H, Shaw RJ & Evans RM. 2008. AMPK and PPARdelta agonists are exercise mimetics. Cell 134, 405–415.
Steensberg A, van Hall G, Keller C, Osada T, Schjerling P, Pedersen BK, Saltin B & Febbraio MA. 2002. Muscle glycogen content and glucose uptake during exercise in humans: influence of prior exercise and dietary manipulation. J Physiol 541, 273–281.
3. Topic: Hydration: What is New?
Presenter: Asker E. Jeukendrup
School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
Discussion:
Hydration has been a heavily debated topic in the past few years. There have been reports of overdrinking and hypernatremia, as well as dehydration and questions about how to balance hydration and fuel intake. Guidelines have been updated to address individual variations in sweat rate and recommend using body weight to gauge losses. In order to combat the issue of depleting glycogen stores and hydration, research has begun to focus on the type of carbohydrate consumed to optimize both. Studies reveal that a mixture of glucose and fructose can result in a faster rate of gastric emptying and superior fluid delivery than the traditional 4–8% glucose solution.
Take home:
Hydration strategies should be practiced and body weight should be considered for assessing an individual’s sweat rate. By combining glucose and fructose in a solution, an athlete can increase performance through higher carbohydrate delivery and ensure hydration for exercise lasting over 90 minutes.
Select reading(s):
Currell K, and Jeukendrup AE. Superior endurance performance with ingestion of multiple transportable carbohydrates. 2008. Med Sci Sports Exerc 40: 275–281.
Noakes TD. 2007. Hydration in the marathon: using thirst to gauge safe fluid replacement. Sports Med 37: 463–466.
Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, and Stachenfeld NS. 2007. American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc 39: 377–390.
4. Topic: Nutrition and the Immune System: What Works and What Doesn’t
Presenter: Michael Gleeson
School of Sport and Exercise Sciences, Loughborough University, Loughborough, United Kingdom
Discussion:
There is some evidence that athletes, particularly those that train harder, are at an increased risk for infections and illnesses that can interrupt training and affect performance. In order to maintain a healthy immune system, athletes require appropriate amounts of calories, protein, vitamin and minerals. If intake is compromised or the provision of essential nutrients decreases, immune function can be suppressed. Despite research investigating individual nutrients, it is apparent that the overall diet must be adequate and supplementation may not provide additional benefits.
Take home:
A well-balanced diet will help to ensure adequate amounts of nutrients that participate in immune strength, such as vitamin C, vitamin A and zinc. Proper recovery nutrition is key to maintain immune function during training.
Select reading(s):
Gleeson M. Can nutrition limit exercise-induced immunodepression? 2006. Nutrition Reviews 64(3): 1–13.
5. Topic: Nutrition and Genetics
Presenter: Mark Tarnopolsky
Department of Pediatrics and Medicine, McMaster University Medical Center, Ontario, Canada
Discussion:
Genetic research as it relates to nutrition and exercise physiology is budding. Investigations into the influence genetics has on skeletal muscle function have looked at the impact carbohydrate availability has on mitochondrial biogenesis and training adaptations. Overall, it appears that dietary manipulation can affect expression, but a performance impact has yet to be delineated. In addition, researchers are looking at the influence creatine monohydrate has on cellular molecular signaling and lead to training enhancements.
Take home:
Stay tuned for new and emerging evidence in the area of genetics and sports nutrition!
Select reading(s):
Deldicque L, Atherton P, Patel R, Theisen D, Nielens H, Rennie MJ, and Francaux M. 2008. Effects of resistance exercise with and without creatine supplementation on gene expression and cell signaling in human skeletal muscle. J Appl Physiol 104: 371–378.
Mathai AS, Bonen A, Benton CR, Robinson DL, and Graham TE. 2008. Rapid exercise-induced changes in PGC-1{alpha} mRNA and protein in human skeletal muscle. J Appl Physiol.
Tunstall RJ, McAinch AJ, Hargreaves M, van Loon LJ, and Cameron-Smith D. 2007. Reduced plasma free fatty acid availability during exercise: effect on gene expression. Eur J Appl Physiol 99: 485–493.
6. Topic: Are Men and Women the Same?
Presenter: Brent C. Ruby
University of Montana, Montana Center for Work Physiology and Exercise Metabolism, Missoula, MT.
Discussion:
There may be subtle differences in fuel metabolism between males and females and during different life stages. Females appear to oxidize more whole body fat compared to males, mainly due to the higher amount of 17-beta estradiol; whereas carbohydrate oxidation is similar. However, in a field situation, the difference in fat oxidation is difficult to mimic.
Take home:
There is insufficient evidence to support that nutrition recommendations should differ between males and females.
Select reading(s):
Harger-Domitrovich SG, McClaughry AE, Gaskill SE, Ruby BC. 2007. Exogenous carbohydrate spares muscle glycogen in men and women during 10 h of exercise. Med Sci Sports Exerc 39(12):2171–9.
Tarnopolsky MA. 2008. Sex differences in exercise metabolism and the role of 17-beta estradiol. Med Sci Sports Exerc 40(4):648–54.
7. Topic: Fat Burning: How and Why?
Presenter: Asker E. Jeukendrup
School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
Discussion:
“Fat burning” is a key phrase among athletes and used to identify activities in training and with the foods consumed. Fat burning is the lay term for fat oxidation. There are many factors under investigation for the effect on fat oxidation: training intensities, gender, altitude, environmental conditions and supplements. The most effective appears to be following moderate intensity exercise and exercise duration with a few exceptions. For the moderate intensity, training status affects fat oxidation—higher intensity for fat oxidation in the trained individual. As exercise duration increase, fat oxidation will increase, unless carbohydrate is provided during the exercise. Most supplements are ineffective or have insufficient data to support their fat oxidizing efficacy, with the exception of caffeine and green tea.
Take home:
The only effective way to oxidize fat is through exercise training, although the best training program remains unclear. There is a great deal of variability among athletes, therefore oxidation rates are unpredictable.
Select reading(s):
Venables MC, Hulston CJ, Cox HR, and Jeukendrup AE. 2008. Green tea extract ingestion, fat oxidation, and glucose tolerance in healthy humans. Am J Clin Nutr 87: 778–784.
Venables MC, Achten J, and Jeukendrup AE. 2005. Determinants of fat oxidation during exercise in healthy men and women: a cross-sectional study. J Appl Physiol 98: 160–167.
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