| Genetics and Sport - Influences on Body Weight
It is important to realize that genetics influence your body weight and not everyone can attain a specific body weight, based on a textbook value of body fatness. It is possible, though never easy, to modify your activities and diet to change body weight to some degree. The decision whether to attempt to reduce body weight also depends on the sport. For example, although a reduction in body weight may help a long distance runner it may have less obvious benefits to the performance of a baseball pitcher.
Does Fat Loss Benefit Athletes?
A low body fat and/or weight can reduce the energy cost of moving your body. Just as strapping a backpack filled with rocks onto your back would accelerate fatigue, extra body fat can make any movement difficult. Excess body fat also reduces the ability to dissipate heat. Thus, an overly fat athlete in football is more likely to overheat during a practice on a hot and humid day than is the leaner athlete doing the same workout. Some athletes are judged partly on their low body fat (e.g. dancers, gymnasts, bodybuilders) or compete in specified weight classes.
Athletes most likely to benefit from body fat loss are those involved in:
- Sports with significant running or jumping.
- Sports competed in hot/humid environments.
- Aesthetic sports.
- Weight-class sports.
Is Body Fat Ever Helpful to Athletes?
Some body fat aids in buoyancy for swimmers (but excess will cause resistance to forward movement in the water). Body fat can also cushion bones and organs for athletes involved in contact sports. Athletes who maximize body mass for greater momentum might benefit form extra body fat provided that they can generate the same speed and power with the extra weight. A difficult decision is defining the line between adequate and too much fat.
Determining Body Weight Goals
A goal body weight should be based on body weight history, sport and position, current body composition, and time remaining until competition. This decision should be made with the advice from a person with the health of the athlete as primary concern (e.g. physician or nutritionist), with input form athletic trainers or possibly coaches and with an assessment of body composition. The American College of Sport Medicine recommends that male athletes should be no lower that 5% and females no lower than 10-12% body fat. Note that these values are for adults; weight loss in teens should be attempted cautiously so as not to hurt growth and development. With the exception of an obese child, weight loss in the child-athlete should never occur. The athlete should consult with a professional such as an athletic trainer or dietitian regarding body weight goals and the decision whether or not to attempt weight reduction.
Once the decision has been made to lose weight, the athlete should be fully assessed (health, diet, and activity) and a plan should be developed to reach the goal. Relevant education and materials should be provided to the athlete with frequent follow up meetings to modify the plan as needed.
An acronym, GOADA, highlights the primary issues for healthy weight loss for athletes:
GRADUAL - Rapid weight loss is more likely to cause loss of muscle and bone tissue and carbohydrate fuel, and promote undesirable changes in hormones, metabolic rate, vigor and mood.
OFF-SEASON - If possible, significant weight loss should occur during the off-season to avoid an energy drain that can compromise training and skill development during the competitive season.
ACTIVITY - Some athletes may be able to increase their calorie burning by adding aerobic conditioning.
DIET - For many, diet will be the focus of weight loss efforts. Research shows that adequate carbohydrate (6-8g/kg), protein (1.5g/kg), vitamins and minerals (at least 100% RDA), and a low fat (15-22% of energy) diet of about 500-1000 kcal less than required for maintaining body weight is best for weight loss.
AVOID - Although tempting for rapid results, dehydration, fad diets, supplements, and drugs should never be used for weight loss. The Center for Disease Control has had reports of adverse health reactions and even death from the use of ephedrine, a supplement in many over the counter weight loss supplements. Dehydration reduces performance, increases risk of heat injury and has contributed to the death of athletes in weight class and endurance sports.
So, before acting on your coach's comments about your weight, get advice from other professionals to decide if you should lose weight. Weight loss can benefit the performance of some athletes, but can have the opposite effect if used unwisely.
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