By Dr Asker Jeukendrup
Many athletes, although not overweight, still would like to lose body weight and in particular body fat. For some this is an advantage because it increases the power to weight ratio (jumping events), for others it is simply because they can reduce the energy expenditure when carrying a lower body weight (running). Research has also shown that another reason why athletes want to get rid of some body fat is simply for the looks. Anyone who has tried to lose weight will know that it is not an easy task. It cannot be stressed enough that weight loss may not always be a good idea and can even be detrimental to performance. There are many mistakes that can be made and the purpose of this short paper is to make you aware of some of these mistakes and give you some guidelines how to lose the weight in a responsible way.
Defining the goals
A first step is to define weight loss goals. In conjunction with the coach and a nutritionist weight loss goals should be identified. These goals should be carefully thought about and defined. Is it really desirable to lose body weight? Weight loss may be useful in some cases but in others it will do more harm than good. Whether it is a good idea or not depends primarily on the body fat percentage. Although individual differences exist, it is not recommended to go below a body fat percentage of about 5% for men and 12-14% for women. Fat has important bodily functions and these will be compromised at extremely low fat levels.
The goals also have to be defined with the time schedule in mind. How much weight do you need to lose and how much time is there to achieve this? A realistic weight loss is about a kilogramme every two weeks, so to lose three kilogrammes at least six weeks are needed. A more rapid weight loss will make it impossible to train adequately.
Energy balance
When the energy intake equals the energy expenditure you will be in energy balance. When you eat less than you burn, you are in negative energy balance and as a result you will lose weight. When you eat more than you expend, you are in positive energy balance - and in this case you will gain weight.
A negative energy balance is necessary to lose weight and there are two ways to induce a negative energy balance:
1. Reducing energy intake
2. Increasing energy expenditure
A combination of these two seems to be the best way to lose body weight.
Besides a negative energy balance, you also must be in negative fat balance in order to lose body fat. This generally means reducing the fat intake, but including aerobic work in training sessions is another way of moving to a negative fat balance.
Reducing the fat intake can be very effective for several reasons:
1. Fat is very energy dense, it has more than twice as much energy as the same weight of carbohydrate or protein.
2. High fat foods generally taste good and this leads to a tendency to eat more. Studies have shown that increasing the fat content of the diet increases the spontaneous intake of food.
3. Fat is efficiently stored and requires very little energy for digestion.
4. Fat intake does not stimulate fat burning.
Common mistakes
We are all impatient, especially with issues like weight loss. We want to lose the weight as fast as possible and we want to see results within a week, but unfortunately this is not realistic. Although it is possible to lose body weight rapidly, this will be mostly water and will reduce performance and the ability to train. Weight loss has to occur slowly and we will have to be very patient. Athletes often try to achieve weight loss during the competitive season, and this will result in underperformance.
Another approach that athletes have tried in the past is not eating in the morning and sometimes even skipping lunch. This is not advised because it will increase hunger feelings later in the day; with one single very large meal, the reduction in intake can easily be compensated.
When losing body weight, there is always the risk of also losing some muscle mass. However, this can partly be prevented by consuming relatively large amounts of carbohydrate. Because it is difficult to train hard when the energy intake is reduced, it is advised to achieve weight loss during the off season.
Below are a few guidelines that might help to achieve weight loss.
1. Determine a realistic body weight goal. The help of a sports dietician is likely to be needed to identify a realistic target weight.
2. Do not try to lose more than 500 grammes per week and do not restrict energy intake by more than 500-750 kcal per day.
3. Eat more fruit and vegetables.
4. Try to choose low-fat snacks.
5. Study food labels and try to find substitutes for high-fat foods. Do not only look at fat content but also the energy content per serving.
6. Limit fat add-ons such as sauces, sour cream and high-fat salad dressings or choose the low fat versions of these products.
7. Try to structure your eating into five or six smaller meals.
8. Avoid eating very large meals.
9. Make sure carbohydrate intake is high and consume carbohydrates immediately after training.
10. Increase the volume of aerobic training to promote fat oxidation. Ideally this exercise is performed daily for at least one hour at a fairly low intensity: it should not be so hard that talking is a problem.
11. A multivitamin and mineral supplement may be useful during periods of energy restriction. You should seek the advice of a nutritionist or dietician.
12. Measure body weight daily and get measurements of body fat regularly (every two months) and keep a record of the changes.
Many of these guidelines need specific nutrition knowledge and therefore athletes are encouraged to seek the advise of qualified registered sports dieticians. Some athletes may have access to the services of the UK Athletics Sports Science Panel. If you are not sure and want to find out if you are one of these athletes, please contact your Regional or High Performance Manager.
