This study aimed to investigate the effects of 6 wk oral supplementation of ß-hydroxy- ß-methylbutyrate (HMB) and HMB combined with creatine monohy-drate (HMBCr) on indices of health in highly trained athletes. Elite, male rugby league players (n = 28) were allocated to 1 of 3 groups: a control group (n = 6), a HMB group (3 g/d; n = 11), or a HMBCr group (3 g/day HMB, 3 g/d Cr; n = 11). Testing prior to, and immediately following, supplementation included a full blood count, plasma testosterone and cortisol, blood electrolytes, lipids, urea and glucose, sperm count and motility, and assessment of psychological state. A 3 X 2 factorial ANOVA revealed no effect of HMB or HMBCr on any of the measured parameters except minor changes in blood bicarbonate and blood monocyte and lymphocyte counts. Blood bicarbonate was significantly decreased in the HMB post-supplementation sample compared to the control and HMBCr groups. Blood monocyte and lymphocyte counts showed no within-group changes for HMB or HMBCr supplementation but were significantly different from the control. However, the majority of these readings remained within normal range. HMB and HMBCr were concluded to have no adverse effects on the parameters evaluated in this study when taken orally by highly trained male athletes over a 6-wk period.
Melissa J. Crowe, Donna M. O’Connor and Joann E. Lukins
Marco Malaguti, Marta Baldini, Cristina Angeloni, Pierluigi Biagi and Silvana Hrelia
The authors evaluated the role of a high-protein, low-calorie, polyunsaturated fatty-acid (PUFA) -supplemented diet on anthropometric parameters, erythrocytemembrane fatty-acid composition, and plasma antioxidant defenses of nonprofessional volleyball athletes. The athletes were divided in two groups: One (n = 5) followed the Mediterranean diet, and the other (n = 6) followed a high-protein, low-calorie diet with a 3-g/day fish-oil supplementation. All the athletes had anthropometric measurements taken, both at the beginning and at the end of the study, which lasted for 2 months. Body-mass index and total body fat were significantly diminished in the second group, while they remained unchanged in the first. Plasma total antioxidant activity (TAA) was significantly increased in the plasma of both groups, with no differences between the groups, suggesting that physical activity, not the different diets, is the main contributor to the increase of plasma TAA. The second group showed a significant increase in erythrocytemembrane PUFA content and in the unsaturation index value (UI) because of the fish-oil supplementation. A high-protein, low-carbohydrate, fish-oil-supplemented diet seems to be useful only when the aim of the diet is to obtain weight loss in a short-term period. The significant increase in the UI of erythrocyte membranes indicates the potential for harm, because a high intake of PUFA might increase susceptibility to lipid peroxidation not counterbalanced by a higher increase in TAA. Adherence to the Mediterranean diet seems to be the better choice.
Humberto José Gomes Silva, Lars Bo Andersen, Mara Cristina Lofrano-Prado, Mauro V.G. Barros, Ismael Fortes Freitas Jr., James Hill and Wagner Luiz do Prado
It is unclear how different exercise intensities affect cardiovascular disease (CVD) risk factors in obese adolescents. The aim of this study was to compare the effects of high-intensity (HIT) vs. low-intensity (LIT) aerobic training on CVD risk factors in obese adolescents.
Forty-three obese adolescents (age: 15.7 ± 1.3 years, BMI: 34.3 ± 4.1kg/m2) participated this study either HIT (corresponding to ventilatory threshold I; N = 20) or LIT (20% below ventilatory threshold I; N = 23) for 12 weeks. All sessions were isocaloric (350 kcal). All participants received the same nutritional, psychological, and clinical counseling. Subjects were assessed in fatness, fitness, lipid profile, and glucose at baseline and after 12 weeks. The CVD risk factors assessed were waist circumference (WC), total cholesterol (TC), high-density lipoprotein (HDL), glucose, and fitness, which were single and clustered analyzed (z scores sum).
Body mass, Body Mass Index, fatness, and WC were improved (P < .001) in both groups. The sum of z scores (WC + TC + glucose-fitness-HDL) improved in both HIT (12 weeks = −2.16 SD; Cohen’s d = .45) and LIT (12 weeks = −2.13 SD; Cohen’s d = .60) without groups differences. Changes in fitness were associated with changes in WC (r = −.48; P = .003).
HIT does not promote any additional improvements in CVD risk factors than LIT in obese adolescents.
Ildus I. Ahmetov, Olga L. Vinogradova and Alun G. Williams
The ability to perform aerobic or anaerobic exercise varies widely among individuals, partially depending on their muscle-fiber composition. Variability in the proportion of skeletal-muscle fiber types may also explain marked differences in aspects of certain chronic disease states including obesity, insulin resistance, and hypertension. In untrained individuals, the proportion of slow-twitch (Type I) fibers in the vastus lateralis muscle is typically around 50% (range 5–90%), and it is unusual for them to undergo conversion to fast-twitch fibers. It has been suggested that the genetic component for the observed variability in the proportion of Type I fibers in human muscles is on the order of 40–50%, indicating that muscle fiber-type composition is determined by both genotype and environment. This article briefly reviews current progress in the understanding of genetic determinism of fiber-type proportion in human skeletal muscle. Several polymorphisms of genes involved in the calcineurin–NFAT pathway, mitochondrial biogenesis, glucose and lipid metabolism, cytoskeletal function, hypoxia and angiogenesis, and circulatory homeostasis have been associated with fiber-type composition. As muscle is a major contributor to metabolism and physical strength and can readily adapt, it is not surprising that many of these gene variants have been associated with physical performance and athlete status, as well as metabolic and cardiovascular diseases. Genetic variants associated with fiber-type proportions have important implications for our understanding of muscle function in both health and disease.
Rudolph G. Villani, Jenelle Gannon, Megan Self and Peter A. Rich
L-Carnitine (L-C) transports fatty acids into mitochondria for oxidation and is marketed as a weight loss supplement. In a double-blind investigation to test the weight loss efficacy of L-C, 36 moderately overweight premenopausal women were pair matched on Body Mass Index (BMI) and randomly assigned to two groups (N = 18). For 8 weeks the L-C group ingested 2 g twice daily of L-C, while the placebo (P) group ingested the same amount of lactose. All subjects walked for 30 min (60—70% maximum heart rate) 4 days/ week. Body composition, resting energy expenditure (REE) and substrate utilization were estimated before and after treatment. For the subjects who completed the study (15 P, 13 L-C), no significant changes in mean total body mass (TBM), fat mass FM, and resting lipid utilization occurred over time, nor were there any significant differences between groups for any variable. Conversely REE increased significantly for all subjects, but no between group differences existed. Five of the L-C group experienced nausea or diarrhea and consequently did not complete the study. Eight weeks of L-C ingestion and walking did not significantly alter the TBM or FM of overweight women, thereby casting doubt on the efficacy of L-C supplementation for weight loss.
Joel B. Mitchell, James R. Rowe, Meena Shah, James J. Barbee, Austen M Watkins, Chad Stephens and Steve Simmons
To examine the effect of prior exercise on the postprandial lipid response to a high-carbohydrate meal in normal-weight (NW = BMI h25) and overweight (OW = BMI ≥25) women (age 18–25), 10 NW and 10 OW participants completed 2 conditions separated by 1 month. In the morning, the day after control (CT = no exercise) or exercise conditions (EX = 60 min cycling at 60% VO2peak), participants consumed a high-carbohydrate meal (80% CHO, 15% protein, 5% fat; 75 kJ/kg BM) followed by 6 hr of hourly blood sampling. Blood was analyzed for triglycerides (TG), blood glucose (BG), and insulin (IN). TG levels over the 6-hr period were lower in NW than OW (p = .021) and lower in EX than in CT (p = .006). Area under the curve (AUC) for TG was lower in NW than OW (p = .016) and EX than CT (p = .003). There were nonsignificant tendencies for reduced BG over time (p = .053) and AUC (p = .083), and IN AUC was lower in EX than in CT (p = .040) for both groups and lower in NW than in OW (p = .039). Prior exercise improved TG levels after a high-carbohydrate meal in both groups, and OW women demonstrated a greater postprandial lipemic response than NW regardless of condition. There were tendencies for improved glucose removal with prior exercise in NW vs. OW. Acute exercise can improve postprandial TG responses and might also improve postprandial BG and IN after a large meal in NW and OW young women.
Adamasco Cupisti, Claudia D’Alessandro, Silvia Castrogiovanni, Alice Barale and Ester Morelli
This study aims to investigate dietary composition and nutrition knowledge of 60 athlete and 59 non-athlete adolescent females (age, 14-18 years), using a 3-day food recall and a questionnaire on nutrition. The reported daily energy intake was similar in athletes and non-athletes, but less than the recommended and the estimated requirements. In the athletes, the energy supply from breakfast was higher than in the non-athletes (18.5 ± 6.6 vs. 15.0 ± 8.2%, p < .005). Energy intake from carbohydrates was higher (53.6 ± 6.2 vs. 49.8 ± 63%, p < .05) and that from lipids was lower (30.4 ± 5.5 vs. 34.2 ± 5.2%, p < .001) in athletes than in non-athletes. Athletes also showed higher fiber (20.0 ± 5.8 vs. 14.1 ± 4.3 g/day, p < .001). iron (10.6±5.1 vs. 7.5 ± 2.1 mg/day,/7 < .001) and vitamin A (804 ± 500 vs, 612 ± 456 μg/day, p < .05) reported intake than non-athletes. Calcium, iron, and zinc intake were less than 100% RDA in both groups. Athletes gave a slightly higher rate of correct answers on the nutrition knowledge questionnaire (77.6 vs. 71.6%,p < .01) than non-athletes. In conclusion, the overall recalled dietary intake and nutrition knowledge of the studied adolescent females show some misconceptions and nutrient deficiencies, but the results in athletes are quite better man in non-athletes, suggesting a favorable role of sport practice on dietary habits and nutrition knowledge.
Mathieu L. Maltais, Karine Perreault, Alexandre Courchesne-Loyer, Jean-Christophe Lagacé, Razieh Barsalani and Isabelle J. Dionne
The decrease in resting energy expenditure (REE) and fat oxidation with aging is associated with an increase in fat mass (FM), and both could be prevented by exercise such as resistance training. Dairy consumption has also been shown to promote FM loss in different subpopulations and to be positively associated with fat oxidation. Therefore, we sought to determine whether resistance exercise combined with dairy supplementation could have an additive impact on FM and energy metabolism, especially in individuals with a deficit in muscle mass. Twenty-six older overweight sarcopenic men (65 ± 5 years old) were recruited for the study. They participated in 4 months of resistance exercise and were randomized into three groups for postexercise shakes (control, dairy, and nondairy isocaloric and isoprotein supplement with 375 ml and ~280 calories per shake). Body composition was measured by dual X-ray absorptiometry and REE by indirect calorimetry. Fasting glucose, insulin, leptin, inflammatory profile, and blood lipid profile were also measured. Significant decreases were observed with FM only in the dairy supplement group; no changes were observed for any other variables. To conclude, FM may decrease without changes in metabolic parameters during resistance training and dairy supplementation with no caloric restriction without having any impact on metabolic properties. More studies are warranted to explain this significant decrease in FM.
Steven Couture, Benoit Lamarche, Eliane Morissette, Veronique Provencher, Pierre Valois, Claude Goulet and Vicky Drapeau
The objectives of this study were to evaluate high school coaches’ knowledge in sports nutrition and the nutritional practices they recommend to their athletes. Forty-seven high school coaches in “leanness” and “non-leanness” sports from the greater region of Quebec (women = 44.7%) completed a questionnaire on nutritional knowledge and practices. “Leanness sports” were defined as sports where leanness or/and low bodyweight were considered important (e.g., cheerleading, swimming and gymnastics), and “non-leanness sports” were defined as sports where these factors are less important (e.g., football). Participants obtained a total mean score of 68.4% for the nutrition knowledge part of the questionnaire. More specifically, less than 30% of the coaches could answer correctly some general nutrition questions regarding carbohydrates and lipids. No significant difference in nutrition knowledge was observed between coaches from “leanness” and “non-leanness” sports or between men and women. Respondents with a university education scored higher than the others (73.3% vs. 63.3%, p < .05). Coaches who participated in coaching certification also obtained better results than those without a coaching certification. The most popular source of information about nutrition used by coaches was the Internet at 55%. The two most popular nutrition practices that coaches recommended to improve athlete performance were hydration and consumption of protein-rich foods. Recommendation for nutritional supplements use was extremely rare and was suggested only by football coaches, a nonleanness sport. Findings from this study indicate that coaches need sports nutrition education and specific training.
Kent C. Hansen and Dale A. Schoeller
Increasing fat content in an isocaloric diet is associated with positive fat imbalance. Exercise attenuates this process, and the authors hypothesized the attenuation was a result of altered postprandial lipid trafficking.
To investigate the effects of prior exercise and nutritional state on the metabolic fate of dietary fat, a study was designed with 4 treatment arms. Energy-balance modifications (fed or fasted) ± exercise were followed by postexercise feeding of 1-14C oleic acid to Sprague-Dawley rats. Fed rats were fed 6 hr before treatment, whereas fasted rats were fasted for 15 hr before treatment with the primary variable being exercise.
14C content of gastrointestinal tract, plasma, breath, muscle (soleus, vastus lateralis [VL], and extensor digitorum longus), liver, and adipose tissue (retroperitoneal and epididymal) was measured at 5 time points postdose (1, 2, 4, 8, and 24 hr).
Compared with matched unexercised controls, fed rats undergoing acute exercise significantly increased recovery of 14C in breath (p = .005) and plasma (p = .001), and trends of increasing 14C recovery occurred in VL (p = .07) and soleus (p = .06). Acute exercise significantly increased recovery of 14C in breath (p = .003), VL (p = .04), and soleus (p = .03) in the fasted study. Acute exercise significantly decreased the trafficking of dietary tracer into adipose tissue in only the fed study (p < .0001).
Although the effect of acute exercise on trafficking dietary fat away from adipose tissue was greater in the fed group than in the fasted, acute exercise had beneficial effects on adipose tissue’s collecting dietary fat when fed or fasted.