Intermittent Fasting: will it Impact Your Training Performance?
Intermittent Fasting is plausibly the most extensively researched type of diet outside of gastric bypass surgery, GLP-1 Medications, and Gradual Weight Loss through caloric restrictions for health purposes, especially fat or weight loss.
Intermittent Fasting is traditionally 8-12 hours without food while incorporating resistance or endurance training during that interrupted food intake timeframe. The one question that is constantly asked about Intermittent Fasting or "IF", is will Intermittent Fasting Impact Training Performance?
In this article I will utilize meta-analysis evidence along with abstracts to answer the training performance question about Intermittent Fasting.
Fasting for Training Performance, lets break down the evidence:
1- Gains:
Similar gains are recorded in virtually all evidence-based studies, fasted -vs- nonfasted. Fasting periods do not negatively impact physical performance compared with a normal pre-exercise diet.
2-Strength and Muscle:
When it comes to resistance exercise training, the trend does change slightly. As Strength and Muscle development all trend towards those who are "fed".
3- Weight Gain/Loss:
Correlation is due to daily caloric intake in all studies.
4- Body Composition:
No Change, unless 20% energy/calorie restriction is continual.. Which reinforces #3, weight gain and loss is fundamentally achieved thru caloric intake.
5- Timing:
Studies show that fasting in the morning, afternoon, evening, or your choice, do not have much of an impact on performance results the next day (see summarization of data below).
What the data suggested that led me to my summarization:
Most of us have heard the statement that if you fast before a workout or cardio based activities, you will burn more fat. Is this true? Although conceivably with Intermittent Fasting you might burn more fat, as fat oxidation level increase roughly 20-48%, burning more for energy initially during a resistance training bout due to insulin reserves being low. Ultimately the body's stored glycogen in the muscle from the previous day's food intake will begin to supply the body with enough energy, as the body will use about 40% of the energy that is stored. The blood supply also has additional triglycerides from protein consumption in it that will replenish the fat that was possibly initially utilized during the beginning of the fasted workout.
So, unless you are at a calorie deficit at the end of your day, the energy percentages will balance themselves out, meaning the initial fat loss due to fasting won't really be lost and will be restored.
BOTTOM LINE:
The human body constantly will load and unload energy micronutrients to get back to energy homeostasis, using carbs here, proteins there, or conceivably the fat in the blood to restore the body to working energy normalcy by the end of the day. This is especially true if energy restriction is returned to normal caloric intake by the end of the day.
What Do I Mean by This:
You could conceivably use more fat as a fuel, and if you implicitly did, it would ultimately rely on your daily energy balance. If you are eating more than you burn, even with fasted workouts, you won't lose fat.
What If you do decide to "IF" before performance or training:
Conceivably you might start slower or feeling a little sluggish with repetitions and output. However, your glycogen stores will begin to supply energy to the body and normal training volume will most likely be equal or more productive by the end of the training session due to your previous day's energy stores.
The Caveat:
If your resistance exercise training is going past the 1-hour threshold or you are a marathon runner, then your performance might plausibly be impacted due to the duration of performance.
FINAL THOUGHTS (IMHO):
Some individuals can't work out before they eat (me). In fact, I train someone who will puke if they eat before dead lifts. Some individuals can run a mile without eating.
If you are obtaining consistent results, then do what works for you. If you aren't getting consistent results, then you might want to consider taking a look at the entire picture of your training performance and program before you blame it on one thing.
Conceivably, based upon the information that I reviewed, Fasted Training could potentially be suboptimal for serious lifters, endurance athletes, marathon runners, or those individuals who train at high volumes.
Disclaimer: Sharing a study in NOT an endorsement. You should read the orginal research yourself and be critical.
