Eating Disorders and Sport Performance

Title: Eating Disorders, Physical Fitness and Sport Performance: A Systematic Review

Journal: Nutrients

Relevant Findings

1. In the general population, eating disorders have a prevalence of 0.6% for anorexia nervosa, 1% for bulimia nervosa, and 3% for binge eating disorder.

2. 13.5% of top athletes experience an eating disorder.

3. A British study found that 16% of female distance runners had eating disorders.

4. The female athlete triad syndrome is characterized by low caloric availability, reduced bone mineral density, and loss of normal menstruation.

5. Long-term eating disorder reduces muscular fitness, which is not completely restored after weight gain. A similar finding was found in the Human Starvation Study.

6. A study showed a positive correlation between low BMI and sport performance among gymnasts. However, the correlation became negative was when BMI became very low.

7. Overtraining syndrome is characterized by fatigue, insomnia, and decreased sport performance.

8. Long-term, extreme dietary restraint negatively impacts sport performance is due to glycogen depletion, accumulation of lactic acid in muscles, dehydration, and loss of muscle mass.

Background

Eating disorders are illnesses characterized by eating disturbances accompanied by marked distress about body appearance. The three main types of eating disorders include anorexia nervosa, bulimia nervosa, and binge-eating disorder. The latter has the highest prevalence in the general population of 3%, followed by 1% for bulimia nervosa, and 0.6% for anorexia nervosa. Notably, the prevalence in top athletes is significantly higher at 13.5%.

Anorexia nervosa is characterized by at least 3 months of severe caloric restriction and weight loss secondary to an intense fear of weight gain and body image distortion. These patients intentionally have a BMI of less than 18.5. There are two subtypes: purging type and restricting type. Patients with purging type anorexia engage in self-induced vomiting, or inappropriate laxative and/or diuretic use. Restricting type anorexia is characterized by caloric restriction and excessive exercising. A special consideration for anorexia nervosa patients is refeeding syndrome. Upon nutritional rehabilitation, the spike in insulin can lead to hypophosphatemia and hypokalemia. In turn, these electrolyte disturbances can cause arrhythmias, seizures, and rhabdomyolysis.

Bulimia nervosa is characterized by recurrent episodes of binge eating with compensatory efforts (e.g., self-induced vomiting) for a minimum of 3 months. In comparison to anorexia, patients with bulimia nervosa have a normal to slightly elevated BMI. Secondary to repeated vomiting, patients may have parotid gland hypertrophy, enamel erosion, and calluses on the back of their hands. Additionally, the loss of gastric secretions classically result in hypochloremic, hypokalemic metabolic alkalosis. Binge-eating disorder is similar to bulimia nervosa, except there is an absence of compensatory behaviours.

BMI and Sport Performance

Eating disorders in elite athletes have a significantly greater prevalence as compared to the general population. This is likely explained by the common belief of athletes and coaches alike that low body weight correlates with greater sport performance. Few studies have supported this notion. One study found a positive correlation between low body weight and sport performance in gymnasts. However, the correlation became negative when the BMI dropped too low. Continued weight loss eventually causes a loss of muscle, negatively impacting sport performance. In some severe cases, athletes with eating disorders can develop symptoms of starvation. These include preoccupation with thoughts of food, increased appetite, negative mood changes, weakness, and decreased concentration.

Excessive Exercise and Sport Performance

Excessive exercising is often recognized when it interferes with work or school, occurs at inappropriate times, or is undertaken despite detrimental effects on health. It is very commonly seen in patients with eating disorders, especially those of greater severity. It is also associated with certain personality traits such as perfectionism and strong work ethic.

In athletes, excessive exercising can be difficult to recognize. They often train multiple times a time, going beyond their training schedule. However, this is not uncommon in competitive athletes. Symptoms that may suggest overtraining and insufficient recovery include fatigue, insomnia, and decreased sport performance.

Dietary Restriction and Sport Performance

Patients with eating disorders often follow very strict dietary rules. For instance, patients may limit what they eat (e.g., only low caloric foods), how much they eat, and when to eat. Although in the short term, caloric deficit and weight loss may increase performance, extreme dietary restraint over a long period negatively impacts sport performance. This is due to glycogen depletion, accumulation of lactic acid in muscles causing pain, dehydration causing cramps, and loss of muscle mass.

Conclusion

Eating disorders are particularly prevalent in athletes, and have a negative effect on physical and psychological health. Coaches should be educated on the clinical features of eating disorders because athletes are at an increased risk of developing eating disorders as compared to the general population. Recognizable manifestations to look out for include low body weight, fatigue, menstrual dysfunction, and decreased performance. Athletes that have a BMI lower than 18.5 should be referred to a specialist and should cease training until they have regained a healthy amount of weight. Contrary to common belief, low body weight can result in reduced sport performance if severe enough. However, future studies are required to explore the correlation between eating disorders and sport performance.