Dietary fats and immune status in athletes: clinical implications

Effect of Low-Fat Dietary Modification on Incident Open-Angle Glaucoma

PURPOSE

We tested whether dietary modification (DM) altered the risk for incident primary open-angle glaucoma (POAG).

DESIGN

Secondary analysis of a randomized intervention trial.

PARTICIPANTS

We linked Medicare claims data to 45 203 women in the Women's Health Initiative Dietary Modification Trial, of which 23 776 participants were enrolled in fee-for-service Medicare Part B and had physician claims.

METHODS

Women were randomized to follow either DM (a low-fat diet, with increased vegetable, fruit, and grain intake) or their usual diet without modification. Nine thousand three hundred forty women were randomized to the DM intervention, whereas 13 877 women were randomized to the control group. Our analyses were based on an intention-to-treat design, with a follow-up to the end of continuous Medicare coverage, death, or the last clams date (12/31/2018), whichever occurred first. Primary open-angle glaucoma was defined as the first claim with the International Classification of Diseases, Ninth or Tenth Revision, codes. Dietary data were assessed using a food frequency questionnaire.

MAIN OUTCOME MEASURES

We used Cox proportional hazards models to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for risk of POAG. Subgroup analyses were performed with P values for interaction.

RESULTS

After exclusion of women with Medicare-derived glaucoma before randomization, the final analysis included 23 217 women (mean age, 64.4 ± 5.8 years). Baseline characteristics were balanced between the intervention and control groups. Primary open-angle glaucoma incidence was 11.1 per 1000 woman-years (mean follow-up, 11.6 ± 7.4 years; mean DM duration, 5.2 ± 3.2 years). We found no overall benefit of DM in reducing incident POAG (HR, 1.04; 95% CI, 0.96-1.12). Race and participant age did not modify this relation (P = 0.08 and P = 0.24 for interaction, respectively). In further analysis of baseline nutrient and food intake stratified by quartile groups, risk of open-angle glaucoma (OAG) in DM participants in the lowest quartile group for percentage calories (kilocalories) from total fat (33.8 or lower) was increased (HR, 1.22; 95% CI, 1.05-1.41; P = 0.007 for interaction).

CONCLUSIONS

Analysis suggests that DM in participants in the lowest quartile group for percentage calories from total fat at baseline increased the risk of incident OAG among women regardless of age or race.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

A mechanosensitive lipolytic factor in the bone marrow promotes osteogenesis and lymphopoiesis

Exercise can prevent osteoporosis and improve immune function, but the mechanism remains unclear. Here, we show that exercise promotes reticulocalbin-2 secretion from the bone marrow macrophages to initiate bone marrow fat lipolysis. Given the crucial role of lipolysis in exercise-stimulated osteogenesis and lymphopoiesis, these findings suggest that reticulocalbin-2 is a pivotal regulator of a local adipose-osteogenic/immune axis. Mechanistically, reticulocalbin-2 binds to a functional receptor complex, which is composed of neuronilin-2 and integrin beta-1, to activate a cAMP-PKA signaling pathway that mobilizes bone marrow fat via lipolysis to fuel the differentiation and function of mesenchymal and hematopoietic stem cells. Notably, the administration of recombinant reticulocalbin-2 in tail-suspended and old mice remarkably decreases bone marrow fat accumulation and promotes osteogenesis and lymphopoiesis. These findings identify reticulocalbin-2 as a novel mechanosensitive lipolytic factor in maintaining energy homeostasis in bone resident cells, and it provides a promising target for skeletal and immune health.

Consistency Is Key When Setting a New World Record for Running 10 Marathons in 10 Days

Background: We describe the requirements and physiological changes when running 10 consecutive marathons in 10 days at the same consistent pace by a female ultra-endurance athlete. Methods: Sharon Gayter (SG) 54 yrs, 162.5 cm, 49.3 kg maximal oxygen uptake (VO₂ max) 53 mL/kg⁻¹/min⁻¹. SG completed 42.195 km on a treadmill every day for 10 days. We measured heart rate (HR), Rating of Perceived Exertion (RPE), oxygen uptake (VO₂), weight, body composition, blood parameters, nutrition, and hydration. Results: SG broke the previous record by ~2.5 h, with a cumulative completion time of 43 h 51 min 39 s. Over the 10 days, weight decreased from 51 kg to 48.4 kg, bodyfat mass from 9.1 kg to 7.2 kg (17.9% to 14.8%), and muscle mass from 23.2 kg to 22.8 kg. For all marathons combined, exercise intensity was ~60% VO₂ max; VO₂ 1.6 ± 0.1 L.min⁻¹/32.3 ± 1.1 mL.kg⁻¹.min⁻¹, RER 0.8 ± 0, HR 143 ± 4 b.min⁻¹. Energy expenditure (EE) was 2030 ± 82 kcal/marathon, total EE for 10 days (including BMR) was 33,056 kcal, daily energy intake (EI) 2036 ± 418 kcal (20,356 kcal total), resulting an energy deficit (ED) of 12,700 kcal. Discussion: Performance and pacing were highly consistent across all 10 marathons without any substantial physiological decrements. Although overall EI did not match EE, leading to a significant ED, resulting in a 2.6 kg weight loss and decreases in bodyfat and skeletal muscle mass, this did not affect performance.

Achieving an Optimal Fat Loss Phase in Resistance-Trained Athletes: A Narrative Review

Managing the body composition of athletes is a common practice in the field of sports nutrition. The loss of body weight (BW) in resistance-trained athletes is mainly conducted for aesthetic reasons (bodybuilding) or performance (powerlifting or weightlifting). The aim of this review is to provide dietary–nutritional strategies for the loss of fat mass in resistance-trained athletes. During the weight loss phase, the goal is to reduce the fat mass by maximizing the retention of fat-free mass. In this narrative review, the scientific literature is evaluated, and dietary–nutritional and supplementation recommendations for the weight loss phase of resistance-trained athletes are provided. Caloric intake should be set based on a target BW loss of 0.5–1.0%/week to maximize fat-free mass retention. Protein intake (2.2–3.0 g/kgBW/day) should be distributed throughout the day (3–6 meals), ensuring in each meal an adequate amount of protein (0.40–0.55 g/kgBW/meal) and including a meal within 2–3 h before and after training. Carbohydrate intake should be adapted to the level of activity of the athlete in order to training performance (2–5 g/kgBW/day). Caffeine (3–6 mg/kgBW/day) and creatine monohydrate (3–5 g/day) could be incorporated into the athlete’s diet due to their ergogenic effects in relation to resistance training. The intake of micronutrients complexes should be limited to special situations in which there is a real deficiency, and the athlete cannot consume through their diet.

Effect of Resistance Training and Diet Intake on Spleen Structure of Ovariectomized Wistar Rats

Introduction Exercise is a key factor in immunity which may be affected by a different diet intake. Thus, we aimed to analyze the effects of diet intake and resistance training on spleen structure of ovariectomized female animals.

Materials and Methods Female Wistar rats were divided into eight experimental groups: sedentary and nonovariectomized animals plus vegetable protein diet (CVS) or animal protein diet (CAS); trained and nonovariectomized rats plus vegetable protein diet (CVT) or animal protein diet (CT); sedentary and ovariectomized groups plus vegetable protein diet (VOS) or animal protein diet (AOS); and trained and ovariectomized animals plus vegetable protein diet (VOT) or animal protein diet (AOT).

Results Groups submitted to both animal protein diet and resistance training, mainly ovariectomized groups, presented a great variability of collagen fibers type III, white pulp, and follicle structure in relation to the other spleen constituents.

Conclusion Resistance training with a vegetable protein diet may play a key factor to maintain spleen’s immune responses across age. However, animal protein diet is suggested to decrease spleen’s immune activity.

Assessment of Nutrition Status in Amateur Windsurfers during Regattas in the Competitive Period-A Field Study

Windsurfing is a demanding activity that requires a high level of physical fitness as well as appropriate training and nutritional strategies. Therefore, the aim of this study was to assess the dietary intake of amateur windsurfers and consider possible dietary mistakes. This field study was conducted among 10 Polish male amateur windsurfers (aged 22 ± 2 years, mean training experience of 9.5 ± 4 years). Dietary intake was assessed using a standardized 3-day food record. The total energy expenditure of each participant was estimated using a mobile fitness application. The daily energy supply in assessed portions of the windsurfers’ food was lower than the estimated demand during the competition. The contribution of macronutrients to the total energy intake adhered to those guidelines, but not with the ones recommended for athletes practicing extreme sports. Daily fluid consumption was insufficient. In the windsurfers’ diet, we noticed low consumption of vitamin D and calcium, while cholesterol, sodium, potassium, and phosphorus intake was too high. Nutritional practices of amateur windsurfers during the competitive period do not comply with current sports nutrition guidelines. The results suggest that windsurfers are in need of nutritional education and dietary counseling in order to meet macronutrient intake targets.

ISSN exercise & sports nutrition review update: research & recommendations

Background

Sports nutrition is a constantly evolving field with hundreds of research papers published annually. In the year 2017 alone, 2082 articles were published under the key words ‘sport nutrition’. Consequently, staying current with the relevant literature is often difficult.

Methods

This paper is an ongoing update of the sports nutrition review article originally published as the lead paper to launch the Journal of the International Society of Sports Nutrition in 2004 and updated in 2010. It presents a well-referenced overview of the current state of the science related to optimization of training and performance enhancement through exercise training and nutrition. Notably, due to the accelerated pace and size at which the literature base in this research area grows, the topics discussed will focus on muscle hypertrophy and performance enhancement. As such, this paper provides an overview of: 1.) How ergogenic aids and dietary supplements are defined in terms of governmental regulation and oversight; 2.) How dietary supplements are legally regulated in the United States; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of nutritional approaches to augment skeletal muscle hypertrophy and the potential ergogenic value of various dietary and supplemental approaches.

Conclusions

This updated review is to provide ISSN members and individuals interested in sports nutrition with information that can be implemented in educational, research or practical settings and serve as a foundational basis for determining the efficacy and safety of many common sport nutrition products and their ingredients.

Altitude training for elite endurance athletes: A review for the travel medicine practitioner

High altitude training is regarded as an integral component of modern athletic preparation, especially for endurance sports such as middle and long distance running. It has rapidly achieved popularity among elite endurance athletes and their coaches. Increased hypoxic stress at altitude facilitates key physiological adaptations within the athlete, which in turn may lead to improvements in sea-level athletic performance. Despite much research in this area to date, the exact mechanisms which underlie such improvements remain to be fully elucidated. This review describes the current understanding of physiological adaptation to high altitude training and its implications for athletic performance. It also discusses the rationale and main effects of different training models currently employed to maximise performance. Athletes who travel to altitude for training purposes are at risk of suffering the detrimental effects of altitude. Altitude illness, weight loss, immune suppression and sleep disturbance may serve to limit athletic performance. This review provides an overview of potential problems which an athlete may experience at altitude, and offers specific training recommendations so that these detrimental effects are minimised.

Fueling the rugby player: maximizing performance on and off the pitch

Fueling the rugby athlete requires a sports nutrition plan that balances energy intake with energy output while providing the athlete with adequate fuel for recovery. The content and timing of meals are fundamental parts of a successful regimen and often require the athlete to participate in extensive planning and preparation to succeed. Carbohydrates, protein, and fat are the primary fuel of the rugby athlete's diet, and proper hydration is imperative to optimize performance. The use of dietary supplements such as energy drinks and caffeine are controversial, and the supplementation of vitamins and minerals is generally not recommended. The use of creatine monohydrate as a supplement to a well-balanced diet has been shown to be safe and effective. With the help of sports nutritionists, team physicians, educated athletes, and coaches, a multifactorial all-encompassing plan is required generally to maximize optimal performance on and off the rugby pitch.

Influence of exercise on nutritional requirements

There is no consensus on the best diet for exercise, as many variables influence it. We propose an approach that is based on the total energy expenditure of exercise and the specific macro- and micronutrients used. di Prampero quantified the impact of intensity and duration on the energy cost of exercise. This can be used to determine the total energy needs and the balance of fats and carbohydrates (CHO). There are metabolic differences between sedentary and trained persons, thus the total energy intake to prevent overfeeding of sedentary persons and underfeeding athletes is important. During submaximal sustained exercise, fat oxidation (FO) plays an important role. This role is diminished and CHO's role increases as exercise intensity increases. At super-maximal exercise intensities, anaerobic glycolysis dominates. In the case of protein and micronutrients, specific recommendations are required. We propose that for submaximal exercise, the balance of CHO and fat favors fat for longer exercise and CHO for shorter exercise, while always maintaining the minimal requirements of each (CHO: 40% and fat: 30%). A case for higher protein (above 15%) as well as creatine supplementation for resistance exercise has been proposed. One may also consider increasing bicarbonate intake for exercise that relies on anaerobic glycolysis, whereas there appears to be little support for antioxidant supplementation. Insuring minimal levels of substrate will prevent exercise intolerance, while increasing some components may increase exercise tolerance.

Physical activity, immunity and infection

During the last few decades, scientific evidence has confirmed a wide range of health benefits related to regular physical activity. How physical activity affects the immune function and infection risk is, however, still under debate. Commonly, intensive exercise suppresses the activity and levels of several immune cells, while other immune functions may be stimulated by moderate physical activity. With this knowledge, the understanding of the relationship between different levels of physical activity on the immune function has been raised as a potential tool to protect health not only in athletes but also in the general population; the mechanisms that translate a physically active lifestyle into good health continue to be investigated. Reviewing the literature, although several outcomes (i.e. the mechanisms by which different levels and duration of physical activity programmes affect numerous cell types and responses) remain unclear, given that the additional benefits encompass healthy habits including exercise, the use of physical activity programmes may result in improved health of elderly populations. Moderate physical activity or moderate-regulated training may enhance the immune function mainly in less fit subjects or sedentary population and the pre-event fitness status also seems to be an important individual factor regarding this relationship. Although adequate nutrition and regular physical activity habits may synergistically improve health, clinical trials in athletes using nutritional supplements to counteract the immune suppression have been inconclusive so far.Further research is necessary to find out to what extent physical activity training can exert an effect on the immune function.

ISSN exercise & sport nutrition review: research & recommendations

Sports nutrition is a constantly evolving field with hundreds of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper is a five year update of the sports nutrition review article published as the lead paper to launch the JISSN in 2004 and presents a well-referenced overview of the current state of the science related to how to optimize training and athletic performance through nutrition. More specifically, this paper provides an overview of: 1.) The definitional category of ergogenic aids and dietary supplements; 2.) How dietary supplements are legally regulated; 3.) How to evaluate the scientific merit of nutritional supplements; 4.) General nutritional strategies to optimize performance and enhance recovery; and, 5.) An overview of our current understanding of the ergogenic value of nutrition and dietary supplementation in regards to weight gain, weight loss, and performance enhancement. Our hope is that ISSN members and individuals interested in sports nutrition find this review useful in their daily practice and consultation with their clients.

Haematological, inflammatory, and immunological responses in elite judo athletes maintaining high training loads during Ramadan

During Ramadan, Muslims abstain from food and fluid intake from dawn to sunset for 1 month. These behavioural changes that accompany Ramadan may impact upon Muslim athletes who continue to train intensely. The aim of the present study was to evaluate the effect of Ramadan intermittent fasting (RIF) on the haematological, inflammatory, and immunological measures in elite judo athletes maintaining their usual high training loads. Haematological markers of inflammation, hormones, and immune status were studied in 15 elite male judo athletes before, during, and after Ramadan. The RIF produced small but significant changes in inflammatory, hormonal, and immunological profiles in judo athletes. Serum C-reactive protein increased from 2.93 +/- 0.26 mg.L-1 pre-Ramadan to 4.60 +/- 0.51 mg.L-1 at the end of Ramadan. Haptoglobin and antitrypsin also significantly increased at different phases during Ramadan, whereas homocysteine and prealbumin remained relatively unchanged. Albumin decreased slightly by mid-Ramadan, then recovered. Immunoglobulin Aincreased from 1.87 +/- 0.56 g.L-1 before Ramadan to 2.49 +/- 0.75 g.L-1 at the end, and remained high 3 weeks after. There were no changes in the leucocyte cell counts throughout the study. The mean blood level of thyroid-stimulating hormone and free thyroxine increased significantly during RIF. Most of these changes were within the normal ranges. These results suggest that athletes who continue to train intensely during Ramadan are liable to experience a myriad of small fluctuations in hormones, immunoglobulins, antioxidants, and inflammatory responses.

Comparisons of food intake between breast cancer patients and controls in Korean women

The purpose of this study was to compare food intakes between Korean breast cancer patients and a healthy control group. We compared the intake of nutrients of 117 food items between Korean breast cancer patients (n=97) and age matched healthy controls (n=97). Nutrient intake was estimated using a quantitative food frequency questionnaire. The mean caloric intake of breast cancer patients and healthy controls was not significantly different. Breast cancer patients consumed significantly less fat and antioxidant nutrients such as vitamin A, retinol, beta-carotene, vitamin C and vitamin E when compared to the control subjects. Among the food items, the intake of eggs (p<0.01), legumes (p<0.05), vegetables (p<0.05), seasonings (p<0.001), and oils and fats (p<0.01) in breast cancer patients was significantly lower than that in the controls. These results suggest that Korean breast cancer patients consumed less amount of soy and vegetables, which are rich source of antioxidant nutrients and phytosterols. Thus, dietary guidance to increase intake of these foods may be beneficial in the prevention of breast cancer.

Zinco no plasma e eritrócito de atletas profissionais de uma equipe feminina brasileira de voleibol

OBJETIVO: Avaliar o estado nutricional relativo ao zinco de 12 atletas profissionais do voleibol feminino. MÉTODOS: Determinou-se a concentração de zinco plasmático e eritrocitário por espectrofotometria de absorção atômica, e avaliou-se a ingestão dietética por meio de registro alimentar de três dias, de 12 atletas profissionais do sexo feminino, integrantes de uma equipe de voleibol de Curitiba, PR, na faixa etária de 18 a 24 anos, no ano de 2003. RESULTADOS: Todas as atletas apresentaram valores normais de zinco plasmático. Quanto ao zinco eritrocitário, 100,00% apresentaram valores abaixo da normalidade. Em relação à ingestão dietética de zinco, 83,33% apresentaram adequação. Decréscimos no conteúdo de zinco eritrocitário podem representar o efeito agudo de exercícios prolongados pela utilização enzimática da superóxido dismutase ou anidrase carbônica. CONCLUSÃO: O estado nutricional das atletas relativo ao zinco parece estar inadequado, pois, apesar dos valores normais para a concentração de zinco plasmático, a concentração eritrocitária esteve abaixo da faixa de normalidade para todas as atletas.

Microbial and Immunological Responses Relative to High-Altitude Exposure in Mountaineers

PURPOSE

High-altitude exposure is often associated with gastrointestinal disorders, inflammation, and an increased risk of infection. We suspected microbial and immunological responses to high-altitude exposure in mountaineers resulting from changes in the balance of the intestinal microflora.

METHODS

We investigated fecal samples and serum of seven mountaineers who took part in a 47-d German expedition to the Nepalese Himalayas in 2002, for microbial response by changes in different fecal bacterial population groups (fluorescent in situ hybridization), immune response by serum levels of IgG-, IgM-, and IgA anti-LPS (E. coli J5), and inflammatory response by serum levels of C-reactive protein (CRP) (ELISA). In addition, measurements of body temperature, pulse rate, arterial oxygen saturation, and questionnaire (Lake Louise score for altitude illness) were performed.

RESULTS

The data indicate a distinct alteration in the composition of the fecal microflora relative to high-altitude exposure above 5000 m. Bifidobacteria and species belonging to the Atopobium, Coriobacterium, and Eggerthella lenta group decreased, whereas potential pathogenic bacteria of the gamma subdivision of Proteobacteria and specific Enterobacteriaceae such as Escherichia coli increased. Possible endotoxemia resulting from the increase of the latter Gram-negative bacteria was indirectly indicated by the reduction in serum levels of IgM- and/or IgA anti-LPS. CRP was elevated relative to high-altitude exposure. The Lake Louise score correlated with the changes in CRP, IgA-, and IgM anti-LPS but did not correlate with the bacterial alterations.

CONCLUSION

Changes in the composition of intestinal microbiota may be associated with indicators of an immunological challenge and may result in an increased health risk of mountaineers during exposure to very high altitude.

ISSN Exercise & Sport Nutrition Review: Research & Recommendations

Sport nutrition is a constantly evolving field with literally thousands of research papers published annually. For this reason, keeping up to date with the literature is often difficult. This paper presents a well-referenced overview of the current state of the science related to how to optimize training through nutrition. More specifically, this article discusses: 1.) how to evaluate the scientific merit of nutritional supplements; 2.) general nutritional strategies to optimize performance and enhance recovery; and, 3.) our current understanding of the available science behind weight gain, weight loss, and performance enhancement supplements. Our hope is that ISSN members find this review useful in their daily practice and consultation with their clients.

Lymphocyte responses to maximal exercise: a physiological perspective

Exercise affects lymphocytes as reflected in total blood counts and the lymphocyte proliferative response. In addition, the production of immunoglobulins is impaired and during exercise the natural killer cell activity increases followed by suppression in the recovery period. Cardiopulmonary adjustments play a major role in lymphocyte response to physical activity. During intense exercise, the activated sympathetic nervous system increases blood flow to muscle as blood flow to splanchnic organs decreases. After exercise, sympathetic tone and blood pressure becomes reduced. The spleen contains lymphocytes and blood resides in gut vessels. A change in blood flow to these organs could affect the number of circulating lymphocytes. Reduced production of immunoglobulins results from suppressed B-cell function and, in response to exercise, mucosal immunity appears to decrease. Pulmonary hyperventilation and enhanced pressure in pulmonary vessels induce increased permeability of airway epithelium and stress failure of the alveolar-capillary membrane during intense exercise. A physiological perspective is of importance for evaluation of the exercise-induced change in lymphocyte function and, in turn, to post-exercise increased susceptibility to infections.

Preventing infectious disease in sports

Preventing infectious disease in sports is fundamental to maintaining team effectiveness and helping individual athletes avoid the adverse effects of illness. Good general hygiene practices, immunization, efforts to minimize exposure to specific diseases, and certain prophylactic measures are essential. Teammates, coaches, athletic trainers, officials, and healthcare providers should actively participate in these preventive efforts, and community public health resources may be involved when appropriate. In addition to treating individual athletes, the team physician's role is to increase awareness, vigilance, and compliance with procedures to prevent the spread of disease.

Phenotypic variability among first-degree relatives with carnitine palmitoyltransferase II deficiency

Carnitine palmitoyltransferase (CPT) II deficiency disorders are clinically very variable. To examine the cause(s) of variable symptoms in first-degree relatives with CPT II deficiency, four sisters with various combinations of mutations and polymorphisms in the CPT2 gene were studied, together with 20 sedentary and 24 trained healthy female subjects. One sister, whose symptoms began at age 7 years, was more severely affected than her older sister, whose symptoms began at age 16 years; both were compound heterozygotes for the common S113L mutation and Q413fs, and for the common CPT2 polymorphisms, V3681 and M647V. A third sister became hypoglycemic with fasting, was heterozygous for the S113L mutation, and homozygous for the polymorphism variants. The fourth sister was asymptomatic, heterozygous for the Q413fs mutation, and homozygous for the normal polymorphisms. Residual CPT II activity in skeletal muscle and cultured skin fibroblasts from the two myopathic sisters, and palmitate oxidation in fibrobasts, were abnormally low; cellular and total body fat oxidation were also diminished. Muscle function and fat oxidation were nomal at rest, but a switch to carbohydrate utilization occurred at lower exercise intensities than in sedentary and trained individuals, respectively. Reliance on carbohydrates during stress and hormonal alterations may explain, in part, the variance in ages of onset and serverity of symptoms in myopathic patients.

Effects of dietary fat and endurance exercise on plasma cortisol, prostaglandin E2, interferon-gamma and lipid peroxides in runners

OBJECTIVE

Exercise and the neuroendocrine and oxidative stress it elicits on immune function is modulated by dietary fat intake. The effects of increasing dietary fat on endurance exercise-induced alterations 80% of VO2max for 2 hours) in the plasma levels of cortisol and prostaglandin E2 (PGE2), interferon-gamma (IFN-gamma) and lipid peroxides were investigated. As higher levels of cortisol, PGE2 and lipid peroxides could be immunosuppressive, the effects of different levels of dietary fat on these measures in runners were determined.

METHODS

Healthy trained runners (males and females) consumed serially 15% fat diet (of daily energy), 30% fat diet and 40% fat diets for four weeks each. In the last week of each diet period the subjects ran to exhaustion at 80% of their VO2max and blood was drawn pre- and post-run. Cortisol, IFN-gamma, PGE2 and lipid peroxides were determined using standard techniques.

RESULTS

Pre-exercise levels of plasma cortisol were elevated, IFN-gamma was unchanged and PGE2 and lipid peroxides decreased on the 40%F diet compared to 30%F and 15%F. Post-exercise levels of plasma cortisol (p < 0.004), PGE2 (p < 0.0057) and lipid peroxide levels increased (p < 0.0001) after endurance exercise on all diets. The rates of increase of plasma cortisol levels during exercise were similar on all three diets. Although absolute cortisol levels were higher in the high fat group, the rate of increase of plasma cortisol level during exercise was similar on each diet. The dietary fat levels did not affect IFN-gamma, however, PGE2 and lipid peroxides decreased with increasing fat at baseline at 40%F level (p < 0.01; 30%F vs. 40% F: p < 0.002; 15%F vs. 40%F: p < 0.007).

CONCLUSIONS

Data from the present study suggest that higher levels of fat in the diet, up to 40%, increase endurance running time without adverse effects on plasma cortisol, IFN-gamma, and lipid peroxide levels.