Study of the energy balance and the nutritional status of highly trained female swimmers

The Potential Role of Nutrition in Overtraining Syndrome: A Narrative Review

Competition between athletes and an increase in sporting knowledge have greatly influenced training methods while increasing the number of them more and more. As a result, the number of athletes who have increased the number and intensity of their workouts while decreasing recovery times is rising. Positive overtraining could be considered a natural and fundamental process when the result is adaptation and improved performance; however, in the absence of adequate recovery, negative overtraining could occur, causing fatigue, maladaptation, and inertia. One of the earliest forms of fatigue is overreaching. It is considered to be an accumulation of training that leads to reduced sports performance, requiring days or weeks to recover. Overreaching, if followed by adequate recovery, can lead to an increase in athletic performance. Nonetheless, if overreaching becomes extreme, combined with additional stressors, it could lead to overtraining syndrome (OTS). OTS, caused by systemic inflammation, leads to central nervous system (CNS) effects, including depressed mood, further inflammation, central fatigue, and ultimately neurohormonal changes. There are therefore not only physiological, biochemical, and immunological but also psychological symptoms or markers that must be considered, independently or together, being intrinsically linked with overtraining, to fully understand OTS. However, to date, there are very few published studies that have analyzed how nutrition in its specific food aspects, if compromised during OTS, can be both etiology and consequence of the syndrome. To date, OTS has not yet been fully studied, and the topic needs further research. The purpose of this narrative review is therefore to study how a correct diet and nutrition can influence OTS in all its aspects, from prevention to treatment.

Nutritional intakes of highly trained adolescent swimmers before, during, and after a national lockdown in the COVID-19 pandemic

Strict lockdown measures were introduced in response to the COVID-19 pandemic, which caused mass disruption to adolescent swimmers’ daily routines. To measure how lockdown impacted nutritional practices in this cohort, three-day photograph food diaries were analysed at three time points: before (January), during (April), and after (September) the first UK lockdown. Thirteen swimmers (aged 15 ± 1 years) from a high-performance swimming club submitted satisfactory food diaries at all time points. During lockdown, lower amounts of energy (45.3 ± 9.8 vs. 31.1 ± 7.7 kcal∙kg BM∙day^-1, p<0.001), carbohydrate (5.4 ± 1.2 vs. 3.5 ± 1.1 g∙kg BM∙day^-1, p<0.001), protein (2.3 ± 0.4 vs. 1.7 ± 0.4 g∙kg BM∙day^-1, p = 0.002), and fat (1.6 ± 0.4 vs. 1.1 ± 0.3 g∙kg BM∙day^-1, p = 0.011) were reported. After lockdown, no nutritional differences were found in comparison compared to before lockdown (energy: 44.0 ± 12.1 kcal∙kg BM∙day^-1; carbohydrate: 5.4 ± 1.4 g∙kg BM∙day^-1; protein: 2.1 ± 0.6 g∙kg BM∙day^-1; fat: 1.5 ± 0.6 g ∙kg BM∙day^-1, all p>0.05), despite fewer training hours being completed (15.0 ± 1.4 vs. 19.1 ± 2.2 h∙week^-1, p<0.001). These findings highlight the ability of adolescent swimmers to alter their nutrition based on their changing training circumstances when receiving sport nutrition support. However, some individuals displayed signs of suboptimal nutrition during lockdown that were not corrected once training resumed. This warrants future research to develop interactive education workshops that maintain focus and motivation towards optimal nutrition practices in isolated periods away from training.

Exercise and Obesity

This paper reviews succinctly the evidence for a role of regular exercise in the prevention and the treatment of obesity and of its metabolic complications. Seventeen propositions relevant to an understanding of the topic are considered. The evidence suggests that regular exercise can be an important factor in the development of sustained negative energy balance conditions provided the volume of activity is high. This implies a program of low to moderate intensity exercise performed on an almost daily basis for at least one hour per session. To induce significant weight and fat losses and to treat overweight and obese patients, compliance to the program for several years becomes a necessity. Exercise increases lipid substrate oxidation and may favor carbohydrate intake for the same amount of energy intake. The acute effects of exercise on resting metabolic rate are well documented, but the long-term influences of exercise training seem to be small and are rapidly suppressed with the cessation of training. The obese benefits also from a regular exercise regimen in terms of improved insulin sensitivity, lipid and lipoprotein profile, and blood pressure, as well as reduced risk of death. Regular exercise, such as walking, is a healthy course of action for the overweight or the obese patients.

Effect of dietary intake on immune function in athletes

Athletes are exposed to acute and chronic stress that may lead to suppression of the immune system and increased oxidative species generation. In addition, the tendency to consume fewer calories than expended and to avoid fats may further compromise the immune system and antioxidant mechanisms. The exercise stress is proportional to the intensity and duration of the exercise, relative to the maximal capacity of the athlete. Muscle glycogen depletion compromises exercise performance and it also increases the stress. Glycogen stores can be protected by increased fat oxidation (glycogen sparing). The diets of athletes should be balanced so that total caloric intake equals expenditure, and so that the carbohydrates and fats utilised in exercise are replenished. Many athletes do not meet these criteria and have compromised glycogen or fat stores, have deficits in essential fats, and do not take in sufficient micronutrients to support exercise performance, immune competence and antioxidant defence. Either overtraining or under nutrition may lead to an increased risk of infections. Exercise stress leads to a proportional increase in stress hormone levels and concomitant changes in several aspects of immunity, including the following: high cortisol; neutrophilia; lymphopenia; decreases in granulocyte oxidative burst, nasal mucociliary clearance, natural killer cell activity, lymphocyte proliferation, the delayed-type sensitivity response, the production of cytokines in response to mitogens, and nasal and salivary immunoglobulin A levels; blunted major histocompatibility complex II expression in macrophages; and increases in blood granulocyte and monocyte phagocytosis, and pro- and anti-inflammatory cytokines. In addition to providing fuel for exercise, glycolysis, glutaminlysis, fat oxidation and protein degradation participate in metabolism and synthesis of the immune components. Compromising, or overusing, any of these components may lead to immunosuppression. In some cases, supplementation with micronutrients may facilitate the immune system and compensate for deficits in essential nutrients. In summary, athletes should eat adequate calories and nutrients to balance expenditure of all nutrients. Dietary insufficiencies should be compensated for by supplementation with nutrients, with care not to over compensate. By following these rules, and regulating training to avoid overtraining, the immune system can be maintained to minimise the risk of upper respiratory tract infections.

Guidelines for daily carbohydrate intake: do athletes achieve them?

Official dietary guidelines for athletes are unanimous in their recommendation of high carbohydrate (CHO) intakes in routine or training diets. These guidelines have been criticised on the basis of a lack of scientific support for superior training adaptations and performance, and the apparent failure of successful athletes to achieve such dietary practices. Part of the problem rests with the expression of CHO intake guidelines in terms of percentage of dietary energy. It is preferable to provide recommendations for routine CHO intake in grams (relative to the body mass of the athlete) and allow flexibility for the athlete to meet these targets within the context of their energy needs and other dietary goals. CHO intake ranges of 5 to 7 g/kg/day for general training needs and 7 to 10 g/kg/day for the increased needs of endurance athletes are suggested. The limitations of dietary survey techniques should be recognised when assessing the adequacy of the dietary practices of athletes. In particular, the errors caused by under-reporting or undereating during the period of the dietary survey must be taken into account. A review of the current dietary survey literature of athletes shows that a typical male athlete achieves CHO intake within the recommended range (on a g/kg basis). Individual athletes may need nutritional education or dietary counselling to fine-tune their eating habits to meet specific CHO intake targets. Female athletes, particularly endurance athletes, are less likely to achieve these CHO intake guidelines. This is due to chronic or periodic restriction of total energy intake in order to achieve or maintain low levels of body fat. With professional counselling, female athletes may be helped to find a balance between bodyweight control issues and fuel intake goals. Although we look to the top athletes as role models, it is understandable that many do not achieve optimal nutrition practices. The real or apparent failure of these athletes to achieve the daily CHO intakes recommended by sports nutritionists does not necessarily invalidate the benefits of meeting such guidelines. Further longitudinal studies of training adaptation and performance are needed to determine differences in the outcomes of high versus moderate CHO intakes. In the meantime, the recommendations of sports nutritionists are based on plentiful evidence that increased CHO availability enhances endurance and performance during single exercise sessions.

The effects of varying dietary fat on the nutrient intake in male and female runners

OBJECTIVE

The present study examined the effects of varying dietary fat levels on nutrients in female and male endurance runners.

METHODS

Three diets (low, medium and high fat) were designed for each subject using their food preferences and three-day food records. Each diet was eaten for 28 to 31 days. The diets were self-selected from seven-day sample menus. Twelve male and 13 female runners between 18 and 55 years of age who averaged 42 miles/week participated in the study. Daily food intakes, activity records and weekly palatability/hunger scales were completed.

RESULTS

Dietary fat intakes, as a percent of total energy intake (%E), averaged 17%E, 31%E, and 44%E on the low, medium and high fat diets, respectively. Energy consumption was less than their estimated energy expenditure (EEE) on all diets. On the low fat diet, the female runners were consuming approximately 60% of their EEE. As dietary fat increased, the difference between calorie intake and estimated energy expenditure became less and the subjects were less hungry on the two higher fat diets. For all subjects, as energy intakes increased, so did carbohydrate intake. Therefore, carbohydrate intake was not different on the two lower fat diets. Irrespective of gender, calcium and zinc intakes, which were below 1989 RDAs, increased with increasing fat intakes, between the low and medium fat diets. Zinc intake was also higher on the highest fat diet. Essential fatty acid intakes for females on the low fat diet were less than 2.5%E. Half of the female runners ate less than the RDA of calcium and zinc on the low fat diet and Fe on the medium fat diet.

CONCLUSION

This study suggests that endurance runners may not be consuming enough calories on a low fat diet and that increasing dietary fat increased energy consumption. On the low fat diet, essential fatty acids and some minerals (especially zinc) may be too low. A low fat diet could compromise health and performance.

Energy expenditure of swimmers during high volume training

The purpose of this study was to examine the total energy expenditure (TEE) of swimmers during high volume training (17.5 +/- 1.0 km.d-1) using the doubly labeled water method. Five female swimmers (age, 19 +/- 1 yr; height, 178.3 +/- 2.2 cm; weight 65.4 +/- 1.6 kg) were administered a dose of 2H2(18)O and monitored for 5 days. Training consisted of two sessions per day, lasting a total of 5-6 h. Energy intake (EI) was calculated from dietary records. Resting energy expenditure (REE) was measured on a non-training day and averaged 7.7 +/- 0.5 MJ.d-1 (1840 +/- 130 kcal.d-1). There were no changes in body weight (day 1, 65.4 +/- 1.6; day 5, 65.2 +/ 1.5 kg) over the measurement period. TEE of the swimmers during the training period averaged 23.4 +/- 2.1 MJ.d-1 (5593 +/- 495 kcal.d-1). EI averaged 13.1 +/- 1.0 MJ.d-1 (3136 +/- 227 kcal.d-1), implying a negative energy balance of 43 +/- 2%. TEE expressed as a multiple of REE was 3.0 +/- 0.2. The results of this investigation describe the total energy demands of high volume swimming training, which may be used to address the dietary concerns of the competitive swimming athlete.

Nutrient intake of endurance runners with ovo-lacto-vegetarian diet and regular western diet

During an endurance run (1,000 km in 20 days) it was investigated whether an ovo-lacto-vegetarian diet (OLVD) could cover the nutritional requirements of endurance athletes. A regular western diet (RWD) was used as reference. Both diets were offered with an energy content of 4,500 kcal per day and an energy percentage of carbohydrate:fat:protein of 60:30:10. The runners were divided into two dietary groups according to their usual dietary habits. The results of the 55 participants who completed the race show that runners from both groups had the same intake of energy, carbohydrate, fat and protein. Runners of the OLVD group consumed more dietary fiber and polyunsaturated fatty acids as well as less cholesterol. With the exception of sodium chloride and cobalamin, the intake of the calculated minerals and vitamins was higher in the OLVD and exceeded the official recommendations. This study shows that an OLVD with a high nutrient density is adequate to cover the nutritional requirements of endurance-athletes. The intake and absorption of iron should be monitored closely in all diet groups.

Non-exercise daily energy expenditure and physical activity pattern in male endurance athletes

The present study was performed to determine whether differences in non-exercise daily energy expenditure (Md,ne) exist between trained and untrained individuals. The data from seven cross-country skiers were compared with those from eight sedentary men. Daily energy expenditure (Md) was determined using the heart rate-oxygen consumption relationship; resting metabolic rate (Mr) was measured using indirect calorimetry. A physical activity questionnaire and ratios of Md or Md,ne to Mr were used as indices of physical activity. Md and Mr were significantly higher in the trained subjects whereas Md,ne was identical in the two groups. The ratio of Md,ne to Mr and the data from the physical activity questionnaire showed that there was no significant difference in daily energy expenditure and physical activity pattern during the non-exercise time. These results suggest that the exercise-induced increase in daily energy requirements is not compensated by a more sedentary life during the other daily activities in these trained men.