Los Angeles Lakers star Luka Dončić used intermittent fasting as a key component of his summer training and nutrition plan, according to a Men’s Health report. While the practice can simplify meal preparation and eliminate late-night snacking, combining a fasting schedule with a rigorous workout routine requires careful timing to protect muscle mass and athletic performance.
How intermittent fasting schedules work
Intermittent fasting restricts daily food consumption to a specific window of time while fasting for the remainder of the day. The most popular format requires a 16-hour fast followed by an eight-hour eating window, such as consuming meals only between 12 p.m. and 8 p.m.
Alternative schedules work for different daily routines as long as the eight-hour consumption window remains intact.
Fasting is not appropriate for everyone, including individuals who are pregnant, have a history of eating disorders, or manage certain medical conditions.
How restricting eating windows helps weight loss and sleep
The primary appeal of intermittent fasting lies in weight loss and reduced overconsumption. Restricting the eating window naturally caps daily calorie intake by preventing late-night trips to the refrigerator.
“Intermittent fasting puts a cap on eating and can eliminate or minimize overconsumption at night,” said Leslie Bonci, R.D., M.P.H, sports dietician for the Kansas City Chiefs, telling Men’s Health.
Bonci said that this restriction can decrease overall calorie intake and support better sleep by giving the stomach time to rest before bedtime. Evidence also suggests the practice can lower blood pressure, reduce the risk of diabetes, and help maintain muscle mass.
Structuring Workouts Around Fasting
Fasting limits the fuel available for high-intensity physical activity, which can lead to weakness and lethargy in the gym. Building significant muscle mass proves difficult while running a caloric deficit.
“Unless you’re a real novice, you can’t build appreciable muscle in a caloric deficit,” said Angelo Poli, ISSA, co-owner of Whole Body Fitness in Chico, CA, and creator of the MetPro diet and exercise app, in an interview with Men’s Health.
Poli explained that the primary goal during a fasting diet should be fat loss rather than muscle growth. “The same activities that build muscle when you're fueled help preserve it when you're in a caloric deficit,” said Angelo Poli, ISSA, co-owner of Whole Body Fitness in Chico, CA, and creator of the MetPro diet and exercise app, in an interview with Men's Health.
Timing Meals for Optimal Lifting
High-intensity activities like weightlifting, sprinting, and CrossFit rely heavily on carbohydrates for energy. Performing these exercises at the end of a fast can diminish strength, speed, and overall performance.
Slimmer athletes worried about muscle definition should schedule their workouts during their daily feeding window.
Bonci recommends sandwiching the workout by consuming one-third of a meal before training and the remaining two-thirds afterward to support recovery and glycogen resynthesis.
Fasted cardio remains safer than fasted weight training because steady-state cardio utilizes stored fat for energy. However, fat burning differs from actual weight loss if a daily caloric deficit is absent.
Common questions about muscle building and fasting safety
Can beginners build muscle while intermittent fasting?
No, experts state that building appreciable muscle requires a caloric surplus, making it difficult for anyone beyond a true novice to add muscle while in a caloric deficit.
Is fasted cardio safe for everyone?
Steady-state fasted cardio is generally safer than fasted weight training because the body relies on fat stores for slow activities, though individuals should stop and eat if they feel light-headed.
Who should avoid intermittent fasting?
Fasting is not appropriate for individuals who are pregnant, have a history of eating disorders, or manage specific medical conditions.
Worth a look