Working out in a fasted state has been touted as a good way to burn fat, while some say suggest taking in caffeine and other nutrients, or eating easily digestible carbohydrates can help increase workout time and/or decrease time to fatigue, or increase recovery time. Different types of workouts have different nutritional needs and length of workout is also a factor. Below we look at studies of fasted state versus not fasted state workouts and performance and weight loss.
Exercising while fasting forces the body to activate the sympathetic nervous system (1) and turns the body into a fat burning machine. When in a fasted state, insulin levels are low and the elevated plasma epinephrine concentration is able to increase the rate of fat oxidation (7). A study found that training in the fasted state consistently stimulates physiological adaptations in muscle that can improve performance (7). For those looking to lose weight, this could also be a good strategy for losing or maintaining weight loss. The easiest way to train in a fasted state is exercising first thing in the morning after a typical 12-hour fast.
As an exception, for long duration, aerobic exercise, it was shown that if protein is consumed pre-workout, that it lengthens the window of consuming protein post-workout (5). Thus, muscle growth was shown regardless of whether protein was consumed pre-workout or in that popular 30-minute to one hour post workout window that is usually reported (6).
Another thing to consider is caffeine consumption. Caffeine has been shown to help with focus during a workout (2) and also to inhibit adenosine receptors, which has been shown to decrease the perception of pain and effort, resulting in improved performance (3). This has big implications for athletes who are competing in events. Moderate to high doses of caffeine ingested less than 1 hour before and during exercise have been long shown to increase endurance exercise performance (8). Lower caffeine doses have also been shown to increase athletic performance both prior and during endurance exercise (8). In addition, these low doses have increased vigilance, alertness, mood, and cognitive processes during and after strenuous exercise (8).
One study tested caffeine in combination with beta-alanine, branched chain amino acids (BCAAs), creatine, vitamin B-6, and vitamin B-12 together. Beta-alanine and creatine have both been shown to delay onset of neuromuscular fatigue, B-6 has been shown to play an important role in metabolic pathways, B-12 with DNA synthesis, and BCAAs improving recovery time (4). Interestingly, the combination of caffeine with these nutrients pre-workout showed greater energy and focus, a quicker reaction time, and delayed fatigue (4).
Since caffeine is low calorie and typically under the caloric load of what is suggested to remain in the fasted state, I believe these two can be combined for performance gains and fat loss. Do you workout in a fasted state? Do you take a supplement or drink caffeine pre-competition?