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Nutrition > The tortoise and the hare - how can athletes safely lose weight?
The tortoise and the hare - how can athletes safely lose weight?
Issue: Volume 27 Number 4
I assume you have seen the St George Bank advertisement where there are a number of families out by a pool having a barbeque. Someone asks a man, ‘what do you do for a living?’, and when the guy responds ‘I’m a bank manager’, the party stops and an awkward silence falls over the crowd. Well, I get the same reaction when I respond ‘dietitian’ when I am out for dinner. People start to wonder whether or not they are allowed to order dessert or should order a ‘skim latte’ instead of the full-fat alternative.
To avoid the social stigma attached to being a ‘dietitian’ at a dinner party, I often respond ‘helicopter pilot’ when asked about my occupation. This way everyone gets to eat dessert and I avoid answering questions about how best to lose weight.
As a sports dietitian, I spend a significant proportion of my consulting time with athletes trying to manipulate their body weight and body composition. However, nutrition is more than simply managing weight. Nutrition has been shown to assist athletes to optimise exercise performance on a number of levels, namely:
- meeting increased daily nutrient requirements
- maximising performance during training and competition
- promoting adequate recovery between exercise sessions
- protecting immune function following strenuous activity
- optimising fuel and fluid stores in preparation for competition.
The challenge for athletes is to take advantage of all the possible benefits of a well-selected food and fluid plan within an ‘energy’ or ‘kilojoule’ budget that enables them to maintain their weight at a level ideal for their sport. This is particularly true for athletes involved in weight category sports or sports that require a low body weight or body-fat level.
Fad diets
The lure of fast weight loss attracts many athletes and coaches to follow fad diets. The Atkins Diet, Zone Diet, Cabbage Soup Diet, South Beach Diet, Fit for Life Diet are all examples of popular fad diets that offer the secret to successful weight loss. Despite basing their success on scientific theory, the real truth is that these diets simply restrict daily dietary energy (kilojoule) intake. Creating a significant mismatch between energy intake and energy expenditure results in rapid weight loss, but are there any health or performance issues related to such extreme dietary interventions?
The lastest information
Dr Anne Loucks of the Department of Biological Sciences, Ohio University recently visited the Australian Institute of Sport to update staff and coaches about the health implications of weight loss in athletes.
Dr Loucks and colleagues have demonstrated that short-term energy restriction has implications on menstrual function and consequently bone health for female athletes. Despite the popular belief that menstrual function in female athletes is affected by per cent body fat, amenorrhoeic and regularly menstruating female athletes span a common range of per cent body fat levels, reported energy intake and energy expenditure.
It appears that low energy availability (perhaps specifically by low carbohydrate availability) causes menstrual dysfunction in female athletes, not the stress of exercise nor a ‘threshold’ per cent body fat. Energy availability is best described as the amount of dietary energy remaining for other physiological functions after energy has been expended for exercise.
Energy Availability = Daily Energy Intake – Exercise Energy Expenditure
Once Energy Availability reaches a threshold of 2530 kcal (105–126 kJ) per kilogram fat free mass per day, substantial impairments of metabolic and hormonal function occur. Low Energy Availability caused by dietary energy restriction or by increased exercise energy expenditure affects performance, growth and health. In females, this is likely to result in a disturbance of reproductive function and menstrual regularity.
An example of low Energy Availability:
|
60kg female athlete with 20 per cent body fat = 48kg |
|
|
Daily Energy Intake is restricted to |
= 10 500 kJ |
|
Exercise Energy Expenditure for three hours of strenuous exercise |
= 5000 kJ |
|
Energy Availability = 10 500 – 5000 |
= 5500kJ |
|
Energy Availability = 5500/48 |
= 114 kJ/kg fat free mass = 27 kcal/kg fat free mass |
So the question is ‘can athletes lose weight safely in order to attain a body weight or physique that optimises sports performance?’
In short, the answer is yes; however, a sustained moderate energy deficit is required to avoid any performance impairment or adverse health effects caused by inadequate fuel and/or nutrient intake. When large reductions in body fat are required, weight loss efforts should be undertaken during a period that is well removed from competition. Realistic goals and an achievable time frame are important for successful long-term loss of body fat or an overall reduction in body weight.
An athlete’s or coach’s decision for an athlete to lose weight or body fat should take into account what is realistically achievable, as well as how important it will be for exercise performance. Consistent weight loss of 0.5 kilogram per week is a suitable goal for most athletes, although slower weight loss would be expected for athletes attaining extremely low body weight or body-fat levels.
Which diet works best?
The ‘one diet fits all’ approach typically does not work. Consideration needs to be given to the demands of the sport, the intensity, frequency and duration of training and an individual’s physical size. It can often be challenging to find the balance between reducing energy intake and providing the nutritional needs of training. Menu patterns must also address the athlete’s appetite, and the social and enjoyment aspects of eating. The input of a sports dietitian can help the athlete to understand their individual requirements and set realistic goals.
Maintain adequate carbohydrate intake
Even when total energy intake is reduced, daily carbohydrate intake needs to be aligned to the daily training load. On high activity days, carbohydrate intake needs to be increased to facilitate optimal exercise performance and promote recovery between exercise sessions. Conversely, on low activity days, carbohydrate intake (particularly from nutrient-poor sources such as cordial, soft drink, lollies and cakes etc.) should be reduced. Adjusting carbohydrate intake based on daily training requires ‘trial and error’. General guidelines can be provided as a starting point, particularly for athletes who must undertake prolonged sessions of moderate and high-intensity activity. Such athletes are encouraged to try to maintain a carbohydrate intake above 5g per kilogram body mass to minimise the impact on training quality. Nevertheless, all athletes should monitor training performances and recovery and adjust their carbohydrate intake when their success at daily refuelling appears to be compromised.
Maintain adequate protein intake
A reduced-energy diet does not mean reducing nutrient-rich protein foods such as meat, chicken, fish, eggs, dairy foods, legumes and cereal foods. Meeting daily protein requirements will help minimise muscle wasting and loss of strength during periods of weight loss. Nutrient-rich protein foods should be spread across meals and snacks over the day. Finally, protein added to a meal or snack can increase the satiety value or ‘fillingness’ of the food choice, helping with appetite control.
Target high fat foods
Energy reductions can be achieved by removing surplus amounts of fat (particularly saturated fat) from the diet. Strategies to meet this goal include choosing lower-fat versions of everyday foods and using low-fat cooking methods where possible. Keeping a food record can be a useful way to see where hidden extras sneak into the diet.
Adapted from:
Burke, L et al. 2004. Current Concepts in Sports Nutrition, Sydney: Nestlé Australia Ltd.
Suggested reading:
Loucks , AB 2004. ‘Energy balance and body composition in sports and exercise’, Journal of Sports Sciences, 22:1–14.
