Allen W. Knehans

Soluble fiber and serum lipids: A literature review

Although fiber has been increasingly recognized as an important dietary constituent, controversy and confusion still exist about the physiologic effects of fiber. Specifically, the independent ability of dietary fiber to lower serum lipid levels is controversial. The purpose of this article is to review available evidence regarding the impact of soluble fibers on serum lipid levels. Soluble fibers appear to have a greater potential to alter serum lipid levels than do insoluble fibers. Significant reduction in the level of serum total cholesterol by soluble fiber was found in 68 of the 77 (88%) human studies reviewed. Of the studies measuring low-density lipoprotein cholesterol, 41 of 49 (84%) reported significant reductions. No significant changes were reported in 43 of the 57 (75%) studies that reported high-density lipoprotein cholesterol and/or in 50 of the 58 (86%) studies that measured triglyceride levels.

Impact of maternal body mass index on neonate birthweight and body composition

OBJECTIVE The purpose of this study was to compare bodyweight and composition (percent fat, fat mass, and fat-free mass) in neonates born to mothers with a normal pregravid body mass index (BMI; < 25 kg/m(2)) vs neonates born to mothers with an overweight/obese pregravid BMI (> or = 25 kg/m(2)). STUDY DESIGN Seventy-two neonates (33 from normal mothers and 39 from overweight/obese mothers) of singleton pregnancies with normal glucose tolerance had their bodyweight and body composition assessed by air-displacement plethysmography. RESULTS After controlling for neonate age at time of testing, significant differences were found between groups for percent fat (12.5 +/- 4.2% vs 13.6 +/- 4.3%; P < or = .0001), fat mass (414.1 +/- 264.2 vs 448.3 +/- 262.2 g; P < or = .05), and fat-free mass (3310.5 +/- 344.6 vs 3162.2 +/- 343.4 g; P < or = .05), with no significant differences between birth length (50.7 +/- 2.6 vs 49.6 +/- 2.6 cm; P = .08) or birthweight (3433.0 +/- 396.3 vs 3368.0 +/- 399.6 g; P = .44). CONCLUSION Neonates born to mothers who have a normal BMI have significantly less total and relative fat and more fat-free mass than neonates born to overweight/obese mothers. Although preliminary, these data suggest that the antecedents of future disease risk (eg, cardiovascular disease, diabetes, and obesity) occur early in life.

Corticosterone's dual metabolic actions

Corticosterone possesses two distinctly opposite metabolic actions. The actions are strictly dose-dependent and are linked to type I and type II corticosteroid receptor binding. These conclusions are drawn from continuous infusion studies where corticosterone yields a bitonic dose-response curve for body weight gain and feeding efficiency. Anabolic at low serum levels, corticosterone concentrations above 2 micrograms/dl bring about an opponent catabolic process that intensifies and eventually masks the anabolic action. Relatively pure type I (aldosterone) and type II (RU28362 and dexamethasone) corticosterone receptor agonists produce opposite monotonic functions that respectively mimic the ascending and descending arms of the corticosterone dose-response curve. Stimulation of either receptor increases the proportion of carcass fat to lean body mass by either increasing carcass lipids (type I) or by reducing protein (type II).

Creatine supplementation during resistance training in college football athletes.

PURPOSE This investigation assessed the effects of a 9-wk regimen of creatine monohydrate (Cr x H2O) supplementation coupled with resistance training on body composition and neuromuscular performance in NCAA Division I football athletes. METHODS Twenty-five subjects were randomly assigned in a double-blind, randomized placebo-controlled design, to a treatment (Cr, N = 9), placebo (P, N = 8), or control group (C, N = 8). The Cr group received 20 g.d(-1) of creatine for the first 5 d in 5-g doses, four times daily, followed by 5 g.d(-1) for the remainder of the study. Each 5-g dose was mixed with 500 mL of glucose solution (Gatorade). The P group received a placebo (sodium phosphate monohydrate; NaH2PO4 x H2O) following the exact protocol as the Cr group. The C group received no supplementation. All subjects resistance trained 4 d.wk(-1). Measurements of neuromuscular performance and body composition were made pre- and post-training after supplementation while monitoring dietary intakes. RESULTS Repeated measures ANOVA indicated significant differences occurred between the Cr group and the other two groups (P and C) for total body weight, lean body mass, cell hydration, strength, peak torque at 300 degrees.s(-1) knee flexion, percent torque decrement, and anaerobic power and capacity. However, percent body fat, peak torque during both knee flexion and extension at 60 and 180 degrees.s(-1), peak torque at 300 degrees.s(-1) during knee extension, global muscular strength (power clean), and extracellular fluid remained statistically unchanged for all groups. CONCLUSIONS Our findings indicate that creatine, supplemented concurrently with resistance and anaerobic training, may positively affect cell hydration status and enhance performance variables further than augmentation seen with training alone.

Chromium picolinate effects on body composition and muscular performance in wrestlers.

PURPOSE The purpose of this study was to assess the effects of 14 wk of chromium picolinate supplementation during the final 16 wk of a preseason resistance and conditioning program on body composition and neuromuscular performance in NCAA Division I wrestlers. During this phase of training, wrestlers are primarily interested in trying to improve physical performance and wrestling technique and are not engaged in severe, acute weight loss practices commonly employed before competition. METHODS This double-blinded, randomized placebo-controlled study involved 20 wrestlers from the University of Oklahoma assigned to either a treatment group (Cr+3; N = 7; 20.4 yr +/- 0.1) receiving 200 micrograms chromium picolinate daily, a placebo group (P; N = 7; 19.9 yr +/- 0.2), or a control group (C; N = 6; 20.2 yr +/- 0.1) using a stratified random sampling technique based on weight classification. Body composition, neuromuscular performance, metabolic performance, and serum insulin and glucose were measured before and immediately following the supplementation and training period. RESULTS Repeated measures ANOVA indicated no significant changes in body composition for any of the groups. Aerobic power increased significantly (P < 0.002) in all groups, independent of supplementation. There were significant trial and group x trial interactions for upper body endurance (P = 0.038) and relative bench press power (P = 0.050). Post-hoc analyses revealed that the C group increased upper body endurance (P = 0.006), but none of the pre- to post-test changes in bench press power were significant. CONCLUSIONS These results suggest that chromium picolinate supplementation coupled with a typical preseason training program does not enhance body composition or performance variables beyond improvements seen with training alone.

Influence of type of mechanical loading, menstrual status, and training season on bone density in young women athletes

Bone mineral density (BMD) variables were compared in 2 groups of women Division I collegiate athletes—gymnasts (GYM) and cross-country runners (CC)—during the preseason and during the competitive season. An osteogenic advantage may exist in women athletes involved in impact loading (gymnastics) over those women in active loading sports like long-distance running. The effects of menstrual status and the time of the training season on BMD also were examined. Dietary intake, menstrual status, BMD, and serum estradiol levels were measured during the preseason and during the competitive season in 26 women athletes (18–22 years of age). GYM had significantly higher BMD (p < 0.05) at all sites for both the pre- and posttests compared to CC. Neither group experienced a significant change (p ≤ 0.05) in BMD between trials for any site; however, CC showed slight decreases at all BMD sites from baseline to the posttest. GYM had a higher prevalence of self-reported menstrual cycle disturbances than CC. No significant difference (p ≤ 0.05) in BMD was found between the eumenorrheic and menstrual dysfunction groups (oligo/amenorrheic). In conclusion, the gymnasts had significantly higher (p < 0.05) BMD than the runners, suggesting BMD is influenced by the type of mechanical loading. Menstrual status did not significantly affect BMD in these women athletes. Cross-country runners were determined to be at greater risk than the gymnasts for low bone mass; thus, it is recommended that these athletes include more high-impact activities in their training regimen to optimize their bone health.

The effects of creatine and whey protein supplementation on body composition in men aged 48 to 72 years during resistance training

Objectives: Creatine and whey protein are supplements believed to have an ergogenic effect. Very little is known regarding the effects of these dietary supplements in older men. The purpose of this study was to determine the effect of creatine and whey protein supplements, consumed independently and in combination, on total and regional body composition in middle-aged men during a resistance-training program.Design, Setting,Participants: Forty-two men were randomly assigned to four groups to receive supplements according to a double-blind protocol. Groups consumed their supplements three times per week immediately following their resistance training sessions. The groups were: 1) placebo (480 ml of Gatorade®); 2) creatine (480 ml of Gatorade® plus 5 grams of creatine); 3) whey protein (480 ml of Gatorade® plus 35 grams of whey protein powder); and 4) whey protein/creatine (480 ml of Gatorade® plus 5 grams of creatine and 35 grams of whey protein powder). All groups participated in resistance training 3 times per week for 14 weeks.Measurements: At the beginning and end of the study, total and regional measures of body composition (DXA) and total (TBW), intracellular (ICW), and extracellular (ECW) body water (Multifrequency BIA) were measured and 3-day diet records were completed.Results: There were significant training effects for regional arm fat (decrease), regional arm bone free-fat free mass (BF-FFM-increase), total body BF-FFM (increase), ICW (increase), and ECW (increase) but no significant group effects and only one significant group by training interaction (ECW). There were no significant changes for total calorie, carbohydrate, fat or protein intake for any of the groups from prestudy to post-study testing.Conclusion: The results from this study suggest that supplementation with creatine, whey protein, or a combination of creatine and whey protein, when combined with resistance training in middle-aged men, have no added benefit to changes that occur to body composition due to resistance training alone.

The gynecologist and the prevention of cardiovascular disease

This article reviews current concepts regarding the prevention of cardiovascular disease for women, with particular attention to modifiable risk factors. The background describes the magnitude of the problem, assesses the quality of the data with respect to risk factor reduction, and emphasizes several important concepts. Changes at menopause, states of endocrine aberration, and benefits and risks of hormone substitution need to be understood in conjunction with all other potentially modifiable and nonmodifiable cardiovascular risk factors. Primary care physicians have a window of opportunity to prevent this number one womens health problem. Integrating behavior modification is the key to prevention as part of the regular gynecologic visit.

Acute, chronic, and interactive effects of type I and II corticosteroid receptor stimulation on feeding and weight gain

Type I (aldosterone) and/or type II (dexamethasone or RU28362) corticosterone receptor agonists were continuously infused in adrenalectomized Sprague-Dawley rats for 28 days at doses of 3.4, 17.2, or 86.2 nmol/day. Additional groups received combined agonist infusions, blank infusions, or sham operations. The type I agonist stimulated body weight gain, and the type II agonists were both suppressive, differing mainly in degree. Although there were a few early effects of these hormones (usually a stage of exaggerated activity), once passed, chronic stimulation was marked by steady or slightly increasing steroid influence on body weight. Throughout the chronic phase of this study there was no departure from a simple opponent model of type I and II ligand actions, and their combination approximated an arithmetic summation of the two separate agonists. This was generally true of feeding as well, although steroid effects on intake were always less pronounced. In contrast to chronic administration, acute combinations of these agonists were highly interactive, producing slight losses than large gains for the aldosterone and RU28362 combinations, but a large gain then small loss for the aldosterone and dexamethasone combination. These results imply that RU28362 and dexamethasone differ in more respects than potency. Because normal endogenous type II stimulation is acute and occurs against a background of type I receptor occupation, mixed agonist interactions are probably the rule for everyday physiological activity, not the exception.

Does nutritional supplementation influence adaptability of muscle to resistance training in men aged 48 to 72 years.

Background and Purpose: Isotonic strength training can result in neuromuscular improvements evidenced in other forms of muscular effort, ie, isokinetic or isometric, especially in young subjects; however, it is unclear if older muscle maintains this same adaptive ability. Additionally, it is not known if the benefits of resistance training can be augmented by creatine and protein supplementation in older men. Therefore, the purpose of this study was to assess changes in isokinetic parameters at varying speeds in men aged 48 to 72 years (mean = 57 ± 2.1) following 16 weeks of isotonic resistance training and creatine and/or protein supplementation. Methods: Forty‐two male subjects were randomly assigned to 1 of 4 training groups: (1) resistance training placebo (n = 10), (2) resistance trained creatine supplemented (n = 10), (3) resistance trained protein supplemented (n = 11), and (4) resistance trained creatine and protein supplemented (n = 11). The program consisted of progressive overload resistance training (3 d/wk) and supplement consumption following the workout. Results: There were significant time effects (P ≤ .05) for peak torque (PT), time to PT, and average power for both the knee extensors and flexors at all velocities. However, no significant group or group by time interactions were noted, indicating that the supplementation protocols had no added benefits. Conclusions: Men aged 48 to 72 years maintained their ability to improve isokinetic muscle function following isotonic training, however, supplementation did not enhance muscle adaptability.