Macronutrient Content of a Hypoenergy Diet Affects Nitrogen Retention and Muscle Function in Weight Lifters

Walberg, Janet L.; Leidy, M. K.; Sturgill, D. J.; Hinkle, Dennis E.; Ritchey, S. J.; Sebolt, D. R.

doi:10.1055/s-2007-1025018

Cited by 75 publications

(49 citation statements)

References 10 publications

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“…Further, it has long been known that if energy intake is insufficient, protein needs are increased (75). With some athletes therefore, especially those who restrict energy intake in an attempt to reduce body weight, it is likely that daily protein needs may be even greater (90).…”

Section: Importance Of Proteinmentioning

confidence: 99%

Protein and Amino Acid Needs of the Strength Athlete

Lemon

1991

International Journal of Sport Nutrition

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The debate regarding optimal proteinlamino acid needs of strength athletes is an old one. Recent evidence indicates that actual requirements are higher than those of more sedentary individuals, although this is not widely recognized. Some data even suggest that high proteinlamino acid diets can enhance the development of muscle mass and strength when combined with heavy resistance exercise training. Novices may have higher needs than experienced strength athletes, and substantial interindividual variability exists. Perhaps the most important single factor determining absolute proteinlamino acid need is the adequacy of energy intake. Present data indicate that strength athletes should consume approximately 12-15% of their daily total energy intake as protein, or about 1.5-2.0 g proteinlkg*d-' (approximately 188-250% of the U.S. recommended dietary allowance). Although routinely consumed by many strength athletes, higher protein intakes have not been shown to be consistently effective and may even be associated with some health risks.Although for most of the 20th century nutritionists have generally believed that proteinlamino acid need is not substantially affected by strength training (87), many athletes, especially body builders, have routinely consumed very high protein diets (41,60). Apparently these individuals think such diets enhance performance, but their opinion is based primarily on hearsay or uncontrolled self-experimentation and therefore lacks the necessary objectivity to convince scientists. However, recent results from several laboratories suggest that the issue of whether such high proteinlamino acid diets are beneficial to strength athletes rnay need to be readdressed (66). This paper reviews new information relative to the previous literature and discusses the potential benefits of protein1 amino acid supplementation for the strength athlete. Importance of ProteinClearly, protein is an essential nutrient for all living organisms. With the exception of water, it is the largest component in our bodies and represents about 15 % of body weight. There are many proteins but each is made up of about 20 amino Peter W.R. Lemon is with the Applied

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Section: Importance Of Proteinmentioning

confidence: 99%

Protein and Amino Acid Needs of the Strength Athlete

Lemon

1991

International Journal of Sport Nutrition

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“…135 However, this dietary strategy does not provide optimal energy stores for a competitive athlete,136,137and performance may suffer. 98,138,139 Ingesting medications that stimulate urine production (eg, diuretics) may have a greater influence on body weight than does altering the diet. Diuretics appropriately prescribed for hypertensive therapy or to reduce edema have been misused by athletes seeking rapid weight loss for competition.…”

Section: Dehydration and Weight Managementmentioning

confidence: 99%

National Athletic Trainers' Association Position Statement: Safe Weight Loss and Maintenance Practices in Sport and Exercise

Turocy

Depalma

Horswill

et al. 2011

Journal of Athletic Training

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Objective: To present athletic trainers with recommendations for safe weight loss and weight maintenance practices for athletes and active clients and to provide athletes, clients, coaches, and parents with safe guidelines that will allow athletes and clients to achieve and maintain weight and body composition goals.Background: Unsafe weight management practices can compromise athletic performance and negatively affect health. Athletes and clients often attempt to lose weight by not eating, limiting caloric or specific nutrients from the diet, engaging in pathogenic weight control behaviors, and restricting fluids. These people often respond to pressures of the sport or activity, coaches, peers, or parents by adopting negative body images and unsafe practices to maintain an ideal body composition for the activity. We provide athletic trainers with recommendations for safe weight loss and weight maintenance in sport and exercise. Although safe weight gain is also a concern for athletic trainers and their athletes and clients, that topic is outside the scope of this position statement.Recommendations: Athletic trainers are often the source of nutrition information for athletes and clients; therefore, they must have knowledge of proper nutrition, weight management W eight classifications in sport (eg, youth football, wrestling, rowing, boxing) were designed to ensure healthy, safe, and equitable participation l ; however, not all sports or activities in which weight might playa role in performance use a weight classification system. In activities such as dance, distance running, gymnastics, and cycling, weight and body composition are believed to influence physical performance and the aesthetics of performance. Yet the governing organizations of these activities have no mandated weight control practices. In 2005, the American Academy of Pediatrics 2 published a general weight control practice guide for children and adolescents involved in all sports.In addition to the potential performance benefits of lean body mass and lower levels of body fat, long-term health benefits include decreased cardiovascular risk factors, reduced triglyceride concentration, possible increases in cardioprotective practices, and methods to change body composition. Body composition assessments should be done in the most scientifically appropriate manner possible. Reasonable and individualized weight and body composition goals should be identified by appropriately trained health care personnel (eg, athletic trainers, registered dietitians, physicians). In keeping with the American Dietetics Association (ADA) preferred nomenclature, this document uses the terms registered dietitian or dietician when referring to a food and nutrition expert who has met the academic and professional requirements specified by the ADA's Commission on Accreditation for Dietetics Education. In some cases, a registered nutritionist may have equivalent credentials and be the commonly used term. All weight management and exercise protocols used to achieve these goals...

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“…Studies from our laboratory have shown that dieting causes loss of lean tissue as measured by net nitrogen loss in the urine (Walberg et al, 1988). The potential value of whey protein isolate on lean tissue loss during energy restriction has not been studied.…”

Section: Whey Protein Isolate May Affect Lean Tissue Massmentioning

confidence: 99%

Effect of Whey Protein Isolate on Oxidative Stress, Exercise Performance, and Immunity

Shute

Rankin

Saker

et al. 2004

Medicine & Science in Sports & Exercise

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The purpose of this study was to evaluate the effectiveness of a whey protein isolate (WPI), a reported glutathione (GSH) booster, on exercise performance, immune function, and antioxidant status during weight maintenance and energy restriction in humans.Twenty well-trained, college age, male cyclists performed a cycling exercise test for 45 min, the first 7 min at 70% of VO 2peak and the remaining 38 min at 55% VO 2peak immediately followed by a performance test set at 90% VO 2peak until exhaustion. Blood samples were collected prior to the exercise test, after 45 min of exercise, within 5 min of exhaustion, and 1 h after exercise. Blood samples were analyzed for GSH, GSH/GSSG ratio, glutathione peroxidase (GPx), lipid hydroperoxides (LPO), phagocytosis, oxidative burst, peripheral blood mononuclear cell (PBMC) proliferation, and PBMC phenotyping.Subjects consumed 40g/day of WPI or casein placebo (P) along with their normal diet for 2 wk, repeated the exercise test, and then began a low energy period continuing the same supplementation for 4 d before the final exercise test. WPI was not associated with superior exercise performance or antioxidant status following exercise or weight loss.WPI supplementation did result in 33% greater lymphocyte proliferation capacity following exercise. Following exhaustive exercise for all trials, tGSH and GPx increased 7% and 11%, respectively, while WBCGSH decreased 13%. For WPI, GPx activity was 10% lower than P following exhaustive exercise for all trials combined. Weight loss (2.67 ± 0.26 kg) resulted in increases in phagocytosis (65%), white blood cell (WBC) iii GSH (40%), and GPx (35%) while decreasing the GSH/GSSG ratio (55%) and LPO (16%). Exhaustive exercise caused a 28% increase in CD3+CD8+ PBMCs and decreased CD3+CD4+ (34%), CD3+ (15%), the CD4+/8+ ratio (45%), and phagocytosis (8%) with all values returning to baseline after 1 h recovery. Supplementation with WPI did not enhance GSH status or exercise performance in trained cyclists, during weight maintenance or energy restriction. Following exercise, WPI is associated with greater lymphocyte proliferation of PBMCs which may help maintain an athlete's health during heavy training or competition.

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Macronutrient Content of a Hypoenergy Diet Affects Nitrogen Retention and Muscle Function in Weight Lifters

Cited by 75 publications

References 10 publications

Protein and Amino Acid Needs of the Strength Athlete

Protein and Amino Acid Needs of the Strength Athlete

National Athletic Trainers' Association Position Statement: Safe Weight Loss and Maintenance Practices in Sport and Exercise

Effect of Whey Protein Isolate on Oxidative Stress, Exercise Performance, and Immunity

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