It amazes me that people still are so keyed in on fasted training to drop body fat.
While personally, I do train prior to eating....I don't do it for the simple thinking it will "lean me out" or help my six pack get here quicker. I do it because of a personal preference of liking to train with less in my stomach because I don't feel logged down.
If I am doing tons of cardio, I am eating prior or drinking as I train, but for everyone who thinks training fasted is the key to dropping pounds quicker....let me show you some research.
First, many may think it will help you regulate your total calories for the day....
In a study of otherwise healthy normal weight males, running for an hour on a treadmill at 70% VO2 max compared to either fasted or after a standardized test meal (30% daily energy intake and mostly carbohydrate) noted that fed exercise suppressed appetite to a greater degree than fasted (both more effective than control) but there was no significant differences in whole-day food intake.
So basically this is saying that yes you may initially eat less...you will pay for it later. Have you ever gone out and did some serious training and not feel hungry or eat beforehand, but later that day or the next day you feel like you can't get enough in you?
This study backs that theory up!
Now, in terms of exercise PERFORMANCE....
As I mentioned earlier, higher intense training requires more energy and will be beneficial to be fed. During maximal exercise attempts (which may include intense resistance training or high intensity interval training) being fed with carbohydrates appears to be more beneficial than fasted training for the purpose of enhancing adaptations to training.
However, In submaximal exercise, there may be no differences at all between fasted and fed training.
For Those Who Think it Will Help Them Burn More Fat...
There is no significant difference in energy expenditure between fasted and fed training as assessed by treadmill running, although RER was lower in fasted (indicative of more fatty acid utilization; fed state consumed a large number of carbohydrates). This increase in fat utilization may underlie the anti-lipidemic benefits of exercise (normalizing the increase of blood lipids that occurs with excess dietary intake of lipids), which does not occur when carbohydrates are preloaded nor is it related to the Glycemic Index of the carbohydrate source. Indirectly, since there are no changes in metabolic rate while a greater percentage of energy comes from fatty acids this reduces glucose oxidation and attenuates the rate of glucose drops induced by endurance exercise (risk of hypoglycemia) when measured over 6 weeks.
What does this mean?
Essentially, you may be using more fat as fuel but it does not conclude in any backed up study that it will over time result in more fat loss than training fed when calories are created equal throughout the day.
One study comparing prolonged cardio exercise in the morning in either a fed or fasted state over 50 days noted that although both groups resulted in a loss of body fat, fed resulted in more weight loss (2.6%) while fasted resulted in less overall weight loss (1.9%) while was able to reach a statistically significant reduction in body fat loss (6.2%) relative to no significant change in fed cardio.
Additionally, another study comparing 6 weeks of fasted or carbohydrate preload training failed to note any significant differences in fat mass or body mass in physically active males given a standardized diet.
So a lot of this "training fasted" to get leaner is a bunch of crap if you ask me....and why some people believe it works is simply because it...well...again, has them eating LESS because they are skipping a meal or snack that puts them into a deficit....AKA....WEIGHT LOSS!
If you enjoy training without food and are not doing any insane amounts of cardio, HIIT, or sessions longer than 90 minutes you are perfectly fine training without food. My main argument is saying that if you are doing it to get your summer beach bod here quicker you may be waiting a long, long time or experiencing the effect of just eating less and thinking it is because of your fasted workouts.
At the end of the day, you do what works for you, but science will tell you otherwise if you think that 60 minute elliptical session will get your abs to pop. Total calories over the course of the day, week and month are what matters most when it comes to weight loss.
Maybe I just ruined your "keto" diet plan now too?
Ooopss!
Have a great weekend!
Deighton K, Zahra JC, Stensel DJ. Appetite, energy intake and resting metabolic responses to 60 min treadmill running performed in a fasted versus a postprandial state. Appetite. (2012)Van Proeyen K, et al. Beneficial metabolic adaptations due to endurance exercise training in the fasted state. J Appl Physiol. (2011)
Trabelsi K, et al. Effects of fed- versus fasted-state aerobic training during Ramadan on body composition and some metabolic parameters in physically active men. Int J Sport Nutr Exerc Metab. (2012)
