Fasted training has once again gained momentum, but is it advisable, even for elite athletes? While it doesn't need to be completely avoided, there are a few benefits. The main concerns with fasted training relate to the frequency and intensity of exercise.
"Training low" refers to performing a session in a fasted state, usually first thing in the morning. While there are some potential benefits, these sessions should be done at the first ventilatory threshold (where breathing rate starts to increase) at an easy/recovery pace, for no more than 60 minutes and ideally no more than twice a week. Identifying this pace can be tricky, and the convenience of training immediately after waking can lead to daily fasted sessions at all intensities.
Fasted training at moderate to high intensity or during longer endurance sessions places significant stress on the central nervous system, leading to the release of stress hormones. Chronically high levels of these hormones can have adverse effects on both health and performance. While some stress is necessary for adaptation, prolonged stress is harmful. Additionally, longer and harder sessions in a depleted state often result in poor performance, poor adaptation, and increased energy consumption later in the day.
Fasted training is particularly problematic for female athletes, whose bodies are more sensitive to low energy availability and elevated stress hormones. This can lead to downregulation of reproductive function, which has many negative health consequences, including deteriorated bone health, impaired cognitive function, reduced athletic performance, and decreased lean muscle mass.
Despite the buzz around fasted training, there is little evidence to support its efficacy, especially if performance gains are the goal. For optimal performance, training sessions should be done in a fed state, defined as the metabolic state occurring 2-4 hours after ingesting food, during which the body is digesting and absorbing nutrients.
Fuelling before training has several positive effects, including:
- Better athletic performance
- Improved glycaemic control throughout the day, preventing blood sugar dips and potential overconsumption of energy
- Regulation of reproductive hormones
- Improved leptin/ghrelin control, essential for maintaining a healthy body weight
Before a training session, it is encouraged to consume 0.5-1.0g of carbohydrate per kg of body weight, depending on the type and duration of exercise. A balanced meal is ideal, but easily digestible carbohydrates before training are sufficient. Good options include a banana, a large glass of juice, a hot cross bun, a slice of toast, or Weetabix.
(Photo: Geoff Lowe)
