What Happens to Your Body When You Strength Train While Fasting

Many people incorporate periods of fasting into their weekly routine to increase energy, lose weight, or improve metabolic health. But should a strength training session take place during this fasting window, or is it better to wait until after having a meal? Here’s what the experts say.

Fasting involves limiting caloric intake for a specific period of time. Intermittent fasting (IF), which is one of the most popular and widely studied forms of fasting, involves alternating periods of fasting and normal calorie intake on a recurring basis. Examples include:

“The benefits of fasting for metabolic health are well documented, including improved insulin sensitivity, reduced inflammation, and in some cases, fat loss,” said Doug Lucas, DO, FAAMM, AOBOS, ABAAR, vice president of women’s health, hormones and lifestyle optimization at LifeMD. Health.

Studies suggest that fasted strength training can be effective and may improve fat loss by promoting the breakdown of stored fat.

However, there is no strong evidence to suggest that fasted strength training is superior to fasted training for muscle growth or performance.

A recent study found that young adults who performed resistance training twice a week for 12 weeks after an overnight fast showed similar improvements in muscle thickness, strength, and power compared to those who trained after eating a high-carb meal.

While some studies found no difference in performance between fasted and non-fasted exercise, others concluded that the practice could actually kill your gym session.

Fasting can impair performance, especially during explosive or high-volume workouts, Lucas warned.

“Fasting is also an added stressor, which may or may not be beneficial depending on your current metabolic state and adrenal health,” he said.

Can strength training on an empty stomach be dangerous?

Some people may feel dizzy or faint when training on an empty stomach, which can be dangerous if they lift heavy weights. Dehydration can increase the risk of negative side effects, so if you’re training on an empty stomach, it’s important to make sure you’re properly hydrated.

Additionally, the effects of strength training during a fast may not affect everyone equally. For example, some women may thrive on strength training on an empty stomach, while others may find that it disrupts their gains and performance while zapping their energy.

Increasing your activity level in general is a healthy way to support weight loss. However, fasted workouts may or may not be helpful, depending on your health goals:

• If fat loss is your goal: Try to workout in the morning. “Try to extend your overnight fast and work out before your first meal,” Lucas suggested.
• If your goal is to improve your physical performance or strength: Lucas does not recommend training on an empty stomach. “A federal state promotes better performance, better strength and better recovery,” he explained.

Ro Huntriss, RD, director of nutrition at Simple, agrees. “Exercising in a nourished state, ideally one to two hours after a balanced meal, further promotes strength, energy and recovery,” Huntriss said. Health.

“For those following a time-restricted diet, such as 16:8, exercising during the eating window or shortly after breaking the fast provides pre- and post-workout nutrition, which is essential for muscle protein synthesis,” she explained.

Different fasting protocols, such as intermittent fasting and extended fasting, can influence how you time your workouts.

Here’s an overview of how each protocol impacts training timing and energy availability:

• 4:8 p.m.: This fasting method involves eating within an 8-hour interval. “A 16-hour fast with an 8-hour eating window may be the most flexible for strength training,” says Morgan Walker, MS, RDN. Health. “Training in the middle of the eating window (for example, 1 to 2 hours after your first meal) will allow for pre- and post-workout nutrition to support muscle retention and performance,” she said.
• One meal a day (OMAD): “If you’re just eating dinner, working out in the morning without refueling afterward could hurt recovery and energy levels,” Lucas warned. If you’re following OMAD, Lucas suggested working out before your meal if your schedule allows.
• Alternate day fasting (ADF): This method can be trickier to balance in terms of training timing. “Recovery windows are compressed, so training days need to be more strategic,” Lucas explained. Lucas recommended working out on fasting days and resting or working on recovery exercises, like stretching, on fasting days, depending on how you feel.

While fasted strength training has its place, the most important aspect of strength training is consistency.

“Until you have a solid, consistent foundation, adding fancy tools like fasted training can derail success,” Lucas said. He recommended not adding tools like fasting until you’ve been training consistently and adding intensity.

“Then, when looking for ways to gradually overload and help you achieve specific goals like fat loss, consider adding fasted training to see how you feel and perform,” he said.