Weight-loss supplements typically fall into 1 of 4 categories depending on their hypothesized mechanism of action: products that block the absorption of fat or carbohydrate, stimulants that increase thermogenesis, products that change metabolism and improve body composition, and products that suppress appetite or give a sense of fullness. Each category is reviewed, and an overview of the current science related to their effectiveness is presented. While some weight-loss supplements produce modest effects (<2 kg weight loss), many have either no or few randomized clinical trials examining their effectiveness. A number of factors confound research results associated with the efficacy of weight-loss supplements, such as small sample sizes, short intervention periods, little or no follow-up, and whether the supplement is given in combination with an energy-restricted diet or increased exercise expenditure. There is no strong research evidence indicating that a specific supplement will produce significant weight loss (>2 kg), especially in the long term. Some foods or supplements such as green tea, fiber, and calcium supplements or dairy products may complement a healthy lifestyle to produce small weight losses or prevent weight gain over time. Weight-loss supplements containing metabolic stimulants (e.g., caffeine, ephedra, synephrine) are most likely to produce adverse side effects and should be avoided.
Melinda M. Manore
This paper presents an overview of vitamin
Melinda M. Manore
Lanae M. Joubert and Melinda M. Manore
Homocysteine is an independent cardiovascular disease (CVD) risk factor modi-fable by nutrition and possibly exercise. While individuals participating in regular physical activity can modify CVD risk factors, such as total blood cholesterol levels, the impact physical activity has on blood homocysteine concentrations is unclear. This review examines the influence of nutrition and exercise on blood homocysteine levels, the mechanisms of how physical activity may alter homocys-teine levels, the role of homocysteine in CVD, evidence to support homocysteine as an independent risk factor for CVD, mechanisms of how homocysteine increases CVD risk, and cut-off values for homocysteinemia. Research examining the impact of physical activity on blood homocysteine levels is equivocal, which is partially due to a lack of control for confounding variables that impact homocysteine. Duration, intensity, and mode of exercise appear to impact blood homocysteine levels differently, and may be dependent on individual fitness levels.
Kathleen Woolf and Melinda M. Manore
The B-vitamins (thiamin, ribofavin, vitamin B-6) are necessary in the energy-producing pathways of the body, while folate and vitamin B-12 are required for the synthesis of new cells, such as the red blood cells, and for the repair of damaged cells. Active individuals with poor or marginal nutritional status for a B-vitamin may have decreased ability to perform exercise at high intensities. This review focuses on the B-vitamins and their role in energy metabolism and cell regeneration. For each vitamin, function related to physical activity, requirement, and status measures are given. Research examining dietary intakes and nutritional status in active individuals is also presented. Current research suggests that exercise may increase the requirements for ribofavin and vitamin B-6, while data for folate and vitamin B-12 are limited. Athletes who have poor diets, especially those restricting energy intakes or eliminating food groups from the diet, should consider supplementing with a multivitamin/mineral supplement.
Jason T. Penry and Melinda M. Manore
Choline plays a central role in many physiological pathways, including neurotransmitter synthesis (acetylcholine), cell-membrane signaling (phospholipids), lipid transport (lipoproteins), and methyl-group metabolism (homocysteine reduction). Endurance exercise might stress several of these pathways, increasing the demand for choline as a metabolic substrate. This review examines the current literature linking endurance exercise and choline demand in the human body. Also reviewed are the mechanisms by which exercise might affect blood choline levels, and the links between methyl metabolism and the availability of free choline are highlighted. Finally, the ability of oral choline supplements to augment endurance performance is assessed. Most individuals consume adequate amounts of choline, although there is evidence that current recommendations might be insufficient for some adult men. Only strenuous and prolonged physical activity appears sufficient to significantly decrease circulating choline stores. Moreover, oral choline supplementation might only increase endurance performance in activities that reduce circulating choline levels below normal.
Katherine A. Beals and Melinda M. Manore
A growing body of evidence suggests that the prevalence of eating disorders and excessive concerns regarding body weight in certain subpopulations of female athletes are increasing. The pressure on female athletes to improve their performances and physiques, coupled with the general sociocultural demand placed on all women to be thin, often results in attempts to achieve unrealistic body size and body weight goals. For some female athletes the pressure to achieve and maintain a low body weight leads to potentially harmful patterns of restrictive eating or chronic dieting. This paper seeks to further delineate the characteristics of a recently identified subclinical eating disorder in female athletes: anorexia athletica. Research studies that support the existence of subclinical eating disorders will be reviewed. In addition, the possible physiological and psychological consequences of subclinical eating disorders will be explored.
Katherine A. Beals and Melinda M. Manore
The purpose of this study was to delineate and further define the behavioral, psychological, and physical characteristics of female athletes with subclinical eating disorders. Subjects consisted of 24 athletes with subclinical eating disorders (SCED) and 24 control athletes. Group classification was determined by scores on the Eating Disorder Inventory (EDI), the Body Shape Questionnaire (BSQ), and a symptom checklist for eating disorders (EDI-SC). Characteristics representative of the female athletes with subclinical eating disorders were derived from an extensive health and dieting history questionnaire and an in-depth interview (the Eating Disorder Examination). Energy intake and expenditure (kcal/d) were estimated using 7-day weighed food records and activity logs. The characteristics most common in the female athletes with subclinical eating disorders included: (a) preoccupation with food, energy intake, and body weight; (b) distorted body image and body weight dissatisfaction; (c) undue influence of body weight on self-evaluation; (d) intense fear of gaining weight even though at or slightly below (-5%) normal weight; (e) attempts to lose weight using one or more pathogenic weight control methods; (g) food intake governed by strict dietary rules, accompanied by extreme feelings of guilt and self-hatred upon breaking a rule; (h) absence of medical disorder to explain energy restriction, weight loss, or maintenance of low body weight; and (i) menstrual dysfunction. Awareness of these characteristics may aid in more timely identification and treatment of female athletes with disordered eating patterns and, perhaps, prevent the development of more serious, clinical eating disorders.
Katherine A. Beals and Melinda M. Manore
This study examined the prevalence of and relationship between the disorders of the female athlete triad in collegiate athletes participating in aesthetic, endurance, or team/anaerobic sports. Participants were 425 female collegiate athletes from 7 universities across the United States. Disordered eating, menstrual dysfunction, and musculoskeletal injuries were assessed by a health/medical, dieting and menstrual history questionnaire, the Eating Attitudes Test (EAT-26), and the Eating Disorder Inventory Body Dissatisfaction Subscale (EDI-BD). The percentage of athletes reporting a clinical diagnosis of anorexia and bulimia nervosa was 3.3% and 2.3%, respectively; mean (±SD) EAT and EDI-BD scores were 10.6 ± 9.6 and 9.8 ± 7.6, respectively. The percentage of athletes with scores indicating “at-risk” behavior for an eating disorder were 15.2% using the EAT-26 and 32.4% using the EDI-BD. A similar percentage of athletes in aesthetic, endurance, and team/anaerobic sports reported a clinical diagnosis of anorexia or bulimia. However, athletes in aesthetic sports scored higher on the EAT-26 (13.5 ± 10.9) than athletes in endurance (10.0 ± 9.3) or team/anaerobic sports (9.9 ± 9.0, p < .02); and more athletes in aesthetic versus endurance or team/anaerobic sports scored above the EAT-26 cut-off score of 20 (p < .01). Menstrual irregularity was reported by 31% of the athletes not using oral contraceptives, and there were no group differences in the prevalence of self-reported menstrual irregularity. Muscle and bone injuries sustained during the collegiate career were reported by 65.9% and 34.3% of athletes, respectively, and more athletes in aesthetic versus endurance and team/anaerobic sports reported muscle (p = .005) and/or bone injuries (p < .001). Athletes “at risk” for eating disorders more frequently reported menstrual irregularity (p = .004) and sustained more bone injuries (p = .003) during their collegiate career. These data indicate that while the prevalence of clinical eating disorders is low in female collegiate athletes, many are “at risk” for an eating disorder, which places them at increased risk for menstrual irregularity and bone injuries.