Effect of Whey Protein in Conjunction with a Caloric-Restricted Diet and Resistance Training

 

 

INTRODUCTION
Lean tissue mass is an important determinant for performance in athletes and a predictor of health in recreationally active adults (8,9,18). Individuals attempting to gain or maintain lean body mass while concurrently losing fat mass often utilize a caloric-restricted or “cut diet”. “Cut diets” are typically 6-12 week protocols in which caloric intake is decreased and energy expenditure is increased in an attempt to reduce body fat mass.

The type of exercise training performed, and the magnitude of the energy deficit influence the tissue lost during the course of the diet, where greater deficits yield a greater body mass loss. Volek et al. (2004) reported that a hypocaloric (very low carbohydrate) diet may result in a preferential loss of total and regional fat mass when compared to a hypocaloric low-fat diet (18,19). Caloric-restricted diets are often used by athletes participating in aesthetic sports, such as dance, diving, gymnastics, and bodybuilding, or in weight class sports, such as wrestling, boxing and martial arts. Non-athletes and recreationally active adults tend to emphasize the importance of reduced weight for general health and fitness, as data routinely show that lowered body fat and BMI are associated with better health outcomes (9,12).

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One of the primary concerns that both athletes and non-athletes face during weight loss interventions is maintaining or increasing lean mass, while decreasing fat mass. Oftentimes, individuals partaking in a caloric-restricted diet, in addition to a vigorous resistance-training regimen, risk creating a negative protein balance, where the rate of protein catabolism exceeds the rate of protein synthesis (6,23). This may lead to muscle degradation, reduced muscle adaptations, performance, function, and recovery if left uncorrected. The expedient ingestion of nutrients after the cessation of exercise is required to help ensure the transition of net muscle protein balance from negative to positive (23).

 

Protein supplementation increases muscle protein synthesis without a corresponding increase in protein degradation, which results in net positive protein balance, allowing for maximal recovery, hypertrophy, and strength gains (6). Therefore, in addition to fat loss, muscle maintenance is of primary concern throughout the duration of the “cut diet”, and requires adequate dietary protein consumption in both athletes and non-athletes (22). Increased consumption of dietary protein during weight loss interventions promotes a greater loss of fat mass and retention of muscle mass, the latter of which directly contributes to elevated resting metabolic rate (8).

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There is a wide range of protein products available for consumers with most claiming to provide enhanced body composition and lean muscle mass. An increasingly popular supplement is whey protein, a high quality complete protein with a high proportion of essential amino acids and branched chain amino acids (e.g. leucine, isoleucine, valine) that results in a more pronounced increase in muscle protein synthesis in response to exercise (3,4,20). However, what is not fully understood is the impact of whey protein supplementation in conjunction with a caloric-restricted diet. The results of this study could have an impact on the supplementation protocol for athletes who need to meet specific weight guidelines (e.g. wrestlers, mixed martial artists, boxers, etc.) and physique athletes. Therefore, the purpose of this study was to determine the effectiveness of a whey protein supplement on body composition, metabolism and muscular fitness in young adult males utilizing a “cut diet” while maintaining regular participation in resistance training.

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METHODS

Experimental Approach to the Problem
In a single-blind, matched group design, resistance trained males participated in a four day/week body building style split resistance training program for eight weeks in conjunction with the pre- exercise, and post-exercise ingestion of a whey protein nutritional supplement (Scivation Whey, Scivation, Inc.) or carbohydrate based nutritional supplement (POWERADE®). In addition, all subjects were provided with a custom designed caloric-restricted diet specifically based on each subject’s individual pre-training body composition. Subjects were instructed that they must follow the diet provided to them for the entire program. Body composition and muscular performance were assessed before and after the eight-week progressive resistance training intervention period. This design allowed for the determination of the effectiveness of the “cut diet” in reducing mass across subjects, while also testing whether the whey supplement differed from the control treatment in regards to body composition and muscle performance.
Subjects
Sixteen apparently healthy, resistance trained (regular, consistent resistance training for at least two years prior to the onset of the study, and currently engaging in whole body resistance training) males between the ages of 21-28 years volunteered to participate in the study. Subjects were excluded if they had less than two years of prior resistance training experience, lower or upper extremity surgery within the past year, recent musculoskeletal injury, epilepsy, or another medical condition that would be exacerbated by the consumption of protein (i.e. excessive consumption of alcohol, diabetes, Lou Gehrig’s disease, or branched-chain keto acidura). All participants completed a confidential Physical Activity Readiness Questionnaire (Par-Q) to ensure that the current health status and physical activity habits for participation in this research was met. Prior to any data collection, all eligible subjects were made aware of the potential risks and benefits of the study and signed university-approved written informed consent documents. The Institutional Review Board of the College of Charleston granted approval of all study procedures.

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Procedures
Body composition and muscular performance testing sessions were performed for all subjects prior to the first dose of supplement and initiation of resistance training and diet program, and within 3 days after the conclusion of the eight-week intervention/training period. Every attempt was made to schedule pre and post testing at the same time of day to avoid variability due to time. Subjects visited the Human Performance Laboratory in the Silcox Center at the College of Charleston for approximately two hours each visit to complete all testing procedures in the same order and were observed by the same research assistants.
Body Composition Assessment
Total body mass was measured on a digital medical scale (Tanita, Tokyo, Japan) and height was measured using a standard medical stadiometer (Seca, Chino, CA). Percent body fat, fat mass, and fat free mass were determined using hydrostatic weighing. Subjects were asked to enter the tank and remove any air bubbles that appeared in or on their clothes, hair, and/or skin. Subjects were then instructed to sit in the submerged chair that was attached to the load sensor. After the subjects were totally submerged, and had exhaled as much air as possible from their lungs, a mass reading was recorded. This was repeated until two measures were within 100 g. Body volume was determined using Archimedes principle, accounting for estimated lung volumes, and body density was determined (body mass/body volume) and entered into the Siri equation for estimation of fat mass and fat free mass (2)
Muscle Performance
Upper and lower body muscular strength was determined using the National Strength and Conditioning Association (NSCA)(14) protocol for a one-repetition maximum (1RM). Each subject performed a 1RM bench press to measure upper body muscular strength, and a 1RM parallel back squat to measure lower body muscular strength. To assess local muscular endurance, 80% of the subject’s 1RM on each lift was used for load and subjects were instructed.

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