For those looking for a sense of renewal after Thanksgiving and heading into the holiday season, fasting could be just the thing. According to a new BYU study, training before fasting can help maximize any internal benefits.
For this study, published in the Journal of Medicine & Science in Sports & Exercise, BYU researchers had 20 adults fast twice for 36 hours while still consuming water. Each of the participants began their fasting after eating the same meal.
Participants started their first fast without training and began their second after a strenuous 45-50 minute treadmill workout. Participants performed hunger and mood assessments every two hours while fasting and recorded levels of B-hydroxybutyrate, a ketone-like chemical.
“We really wanted to see if we could change the metabolism during fasting through exercise, especially how fast the body goes into ketosis and makes ketones,” said BYU Ph.D. student Landon Deru in a press release.
Ketosis is a metabolic condition that occurs in response to low glucose availability in the body, which is typically caused by eating minimal carbohydrates or fasting. In response to low glucose levels, the body begins to break down fat in the body, which produces ketones. Ketones act as an energy source for the brain and heart and can be useful in fighting certain diseases.
According to the study, when participants fasted after exercising, they were able to reach ketosis three and a half hours earlier than when they did not exercise before fasting. In addition, they produced 43% more B-hydroxybutyrate.
When participants fasted without exercising, they did not reach ketosis until 20 to 24 hours after fasting. Researchers theorize that exercise before fasting causes the body to burn much of the stored glucose, creating a faster transition to ketosis.
“For me, the hardest time for fasting is the period between 20 and 24 hours, so if I can do something to stop fasting within 24 hours and get the same health results, it is beneficial,” says Bruce Bailey, a BYU professor at training science. study co-author, said in a press release. “Or if I fast for my usual 24 hours but start training, I get even more benefits.”
Bailey noted that carb-loading, or eating a particularly large meal before fasting, distorted the positive effect of exercising before fasting and could prevent the body shape from going into ketosis for days due to excess glucose. He also said that certain people, like those with type 1 diabetes, should not fast and that no one should fast all the time.
The study did not determine how much or what type of exercise each person should participate in to reap the benefits of exercising before fasting. However, researchers believe that the more calories burned, the better.
“You can get a pretty good estimate of how many calories you burn in most exercises, and the more carbohydrates you burn (without overdoing it or harming yourself), the better you set the stage for starting ketosis early in your fast. , “said Deru.