Many female athletes desire a lean physique. This tends to be driven by performance as competitive standards get higher as well as a desire to achieve a socially acceptable weight and shape. For most sports, a low bodyfat percentage means better performance, while a high bodyfat percentage can reduce speed, agility and efficiency of movement.
What is my ideal body fat percentage?
Excessive bodyfat tends to reduce speed, agility, balance and endurance and increase fatigue. It slows you down and reduces your mechanical efficiency. In general, low body levels are associated with better performance. But being lean will not guarantee you athletic success nor is there a linear relationship between bodyfat percentage and performance.
For each person there is an optimal fat percentage at which she will perform at her best. For this reason, sports physiologists believe that a range of values for body fat percentage should be established outside of which your performance and/or health is likely to be impaired. Staying below the upper limit should be your target but lower is not necessarily better.
What is the minimum amount of body fat I need?
A certain amount of bodyfat is vital for the body to function normally and healthily. In fact striving for a bodyfat percentage that is too low can be dangerous.
Your total body fat percentage can be divided into two categories:
*Essential Body Fat: for the body to function normally and healthily a certain amount of bodyfat is required. This is called essential fat and includes the fat which forms part of your cell membranes, brain tissue, nerve sheaths, bone marrow and the fat surrounding vital organs where it provides cushioning and protection.
For both men and women this amounts to about 3% of bodyweight. However, women also store fat in the breasts and around the hips and this accounts for a further 5 – 9% of bodyweight. Thus, for women the average amount of essential fat is 8 – 12% of bodyweight and for men 3%.
*Storage Fat: this consists mainly of fat deposited just under the skin (subcutaneous fat) and fat in the abdominal cavity (intra-abdominal fat). Some storage fat is required for good health. It’s used to provide energy for day to day activities as well as for sports and exercise.
Although not all of this is available as fuel the amount of storage fat is much greater than that needed for immediate energy production. Even in an event as long as a marathon, only about 200g of bodyfat supplies energy.
How low is too low?
“Reducing your body fat may lead to improvements in performance but if the loss is too rapid or too severe, then your performance and health may suffer”
Reducing your bodyfat may lead to improvements in performance but if the loss is too rapid or too severe, then your performance and health may suffer. Trying to achieve a body fat percentage that is so low it affects your essential fat stores is NOT good for your health. So women should not let their bodyfat levels go below about 10 – 15%.
This isn’t a target level, rather a minimum level below which your health and performance will suffer. Attaining extremely low levels of bodyfat invariably involves chronic under-eating. Nutrient deficiencies and fluid/electrolyte imbalance from low food intake can lead to impaired immunity, increased risk of infection and illness, loss of reproductive function and serious medical conditions such as dehydration, and starvation.
For female athletes, low bodyfat levels cause a drop in oestrogen (the female sex hormone) levels. This in turn can lead to a loss of bone mass and increased risk of fracture (osteoporosis). The female athlete triad highlights the problem. This refers to the presence of three conditions often found in female athletes who lose too much bodyfat – eating disorders, amenorrhoea (cessation of periods or irregular periods) and decreased bone mass.
The medical complications of this triad involve almost every body function and include the cardiovascular, endocrine, reproductive, skeletal, gastrointestinal, renal and central nervous systems.
What are the risks of low body fat levels?
Although there is a strong link between bodyfat levels and exercise performance, it’s important to recognise that reducing body fat levels will not automatically guarantee success and may even be counter productive. If you cut your food intake too drastically not only will your training suffer, but the risk of illness and injury increases too.
Amenorrhoea tends to be triggered once bodyfat levels fall below 15 – 20%, although the threshold varies from one person to another. This fall in bodyfat, together with other factors such as low calorie intake and heavy training, is sensed by the hypothalamus of the brain, which then decreases its production of the hormone (gonadotrophinreleasing hormone) that acts on the pituitary gland.
This in turn reduces the production of important hormones that act on the ovaries (luteinising hormone and follicle-stimulating hormone), causing them to produce less oestrogen and progesterone. The end result is a deficiency of oestrogen and progesterone and a cessation of menstrual periods. Low bodyfat levels also upset the metabolism of the sex hormones, reducing their potency and thus fertility.
Therefore, a very low bodyfat level drastically reduces a woman’s chances of getting pregnant. However, the good news is that once your bodyfat level increases over your threshold and your training volume is reduced, your hormonal balance, periods and fertility generally return to normal. Amenorrhoea can result in a loss of bone minerals and a reduction in bone density.
In younger (premenopausal) women, this is called osteopenia (i.e. lower bone density than normal for age), which is similar to the osteoporosis that affects post-menopausal women, where bones become thinner, lighter and more fragile. Amenorrhoeic athletes, therefore, run a greater risk of stress fractures.
What is a healthy way to reduce body fat?
For healthy weight loss, the American College of Sports Medicine recommend athletes reduce their calorie intake by approximately 10–20%. approximately 10–20%. This modest calorie drop should produce a weight loss in the region of 0.5kg per week as well avoid the metabolic slowdown that is associated with more severe calorie reductions.
You can achieve this by cutting fat and only if necessary, carbohydrate intake by around 10 – 20%. Reducing your carbohydrate intake further may result in a loss of strength and endurance. Aim to get 20 – 25% of total calories from fat and 1.2 – 1.7 g protein/kg body weight daily.
*Every woman (and man) has an optimal fat percentage at which she will perform at her best – for most elite female athletes, this lies between 12 and 18%.
*A certain amount of bodyfat is vital for the body to function normally and healthy.
*Excess bodyfat adds to the weight that has to be carried and thus increases the energy cost of exercising. Reducing this will lead to improvements in performance but if the loss is too rapid or too severe, then your performance and health may suffer.
*Severe reductions in bodyfat can result in low oestrogen levels, loss of bone mass and increased risk of fracture.
*To lose bodyfat, you have to expend more energy than you consume – a combination of diet and activity is more likely to result in long-term success than diet or exercise alone.
*For healthy weight loss, the American College of Sports Medicine recommend athletes reduce their calorie intake by approximately 10–20%.