Can you fast and work out at the same time? The short answer is yes, but the longer answer is that it depends, and there are some things to keep in mind.
Below, we discuss intermittent fasting and the safety considerations of combining this restricted eating approach with workouts.
What is Intermittent Fasting?
Intermittent fasting or IF is when you switch between periods of fasting or not eating and eating. You might follow a regular schedule, such as fasting every day until noon. You might also switch it up and fast some days and not others, or choose different eating windows on varying days of the week.
IF is one of the most popular health trends, and there’s evidence that it is effective for weight loss and may have other benefits.
For example, studies show that fasting periods can positively affect weight and your brain and may extend your life.
When you fast, your body changes on a cellular level. One way this happens is through the adjustment of hormone levels that make your body fat more accessible. Your body begins repair processes, and your gene expression can change.
Intermittent fasting is different from the patterns of food consumption most people follow. Typically, Americans will eat during their waking hours throughout the day.
You might have three meals a day, snacks, and then if you’re not exercising, each time you eat, your body is using the calories you just consumed instead of burning your stored fat. When you fast, you’re extending the period your body is burning the calories you eat, and then you start to burn fat.
Specific things that happen during fasting include:
- Your levels of human growth hormone tend to go up dramatically. When your HGH levels go up, it helps you gain muscle mass and fat loss.
- Insulin levels drop, and insulin sensitivity improves. When your insulin levels are lower, it helps make the stored body fat you’re holding onto more accessible.
- Your cells start a repair process when fasting. Autophagy can happen, which is a process where your cells digest and then remove the old and dysfunctional proteins that build up inside them.
- Your gene function changes beneficially for protection against disease and to promote longevity.
- Intermittent fasting helps with weight loss in different ways. First, you’re likely to consume fewer calories because you’re restricting the times you eat. There are also changes to your hormones to facilitate weight loss. For example, there’s an increase in the release of norepinephrine, which is a fat-burning hormone. The changes in hormones stemming from short-term fasting could increase your metabolic rate by up to 14%.
- Studies show IF can reduce markers of inflammation. Chronic inflammation is a cause of many chronic illnesses, including cancer.
- Intermittent fasting can benefit heart health, including reducing harmful LDL cholesterol, blood sugar, and blood triglycerides, which are heart disease risk factors.
- In animal studies, intermittent fasting has shown the potential to prevent cancer.
- As you fast, it increases BDNF, which is a brain hormone. The increases in BDNF can help your brain grow new nerve cells, and it’s a practice that, when done regularly, could protect against Alzheimer’s and similar brain diseases.
- In a study of rats, they had lifespans that were anywhere from 36-83% longer when they fasted.
Is Fasting Safe?
You should always talk to your doctor about fasting if you have underlying health conditions, but in general, it’s considered safe. You may feel hungry at first, or you could experience some weakness or declines in performance, but as you get used to fasting, these effects tend to go away.
Women should be careful with intermittent fasting because it’s been shown to affect their menstrual cycle in animal studies. For women, doing shorter windows of fasting may be a good option.
Common Ways to Fast
You can customize intermittent fasting to make it work for you. One of the most common approaches is restricting your eating to a six-to-eight-hour period every day.
If you choose the common 16/8 fasting approach, you eat for eight hours and fast for 16. This tends to be a pattern that people find easy to stick to over the long term.
Then another way to fast is called the 5:2 approach. With the 5:2 approach, you eat regularly five days a week. Then, on the other two days, you limit yourself to a meal consisting only of 500-600 calories.
You can go long periods without eating, like 24 or 36 hours, but these can be more difficult and might encourage your body to store more fat because it thinks it’s starving.
Are Intermittent Fasting and Working Out Safe Together?
You can maintain your exercise routine during your intermittent fast. Intermittent fasting and working out can work together to facilitate more benefits.
- If you do fasting exercise, it may affect your metabolism positively and help with optimal blood sugar levels.
- You will burn more fat when fasting and working out because your stored carbs are depleted. Those stored carbs are also known as glycogen.
- You should be aware that there may be some downsides if you exercise in a fasted state. For example, you might break down muscle to use protein for fuel. You could also have less energy, and over the long-term, you could experience a slowdown in your metabolism.
For some people, rather simultaneously intermittent fasting and working out, it’s more beneficial to schedule your workouts during your eating window.
This will let you fuel your workouts, especially if you’re going heavy on strength training or doing high-intensity exercises.
Everyone is different, and that’s the biggest thing to remember. Some people like to work out on an empty stomach, which is fine if you’re refueling appropriately. On the other hand, some people need food for peak performance during their workouts.
Best Pre-workout Foods for Weight Loss & Strength
If you decide to do your workouts after your eating window begins, the foods you choose will help you maintain your energy and build muscle. Of course, choosing the wrong foods and pre-workout meals can also negatively impact your fitness goals.
- Your muscles use the glucose that comes from carbohydrates for fuel. If you decide to eat before a workout, you should consider certain types of carbs. Carbs can increase your glycogen stores and help you with improving your intensity and output.
- Pre-workout protein consumption can also help your performance. Research shows that eating protein either by itself or with carbs before you work out can boost your muscle protein synthesis.
- Fat can be the right pre-workout fuel if you’re going to do more prolonged exercise at a low or moderate intensity. For example, having healthy fats can help with endurance runs.
- Unless you’re fasting, try to eat a meal with carbs, protein, and fat around two to three hours before exercising.
- Foods to have before a workout session might include eggs and whole-grain toast, lean protein with brown rice and vegetables, or a protein smoothie.
- Protein bars are another convenient option for muscle growth and to give you energy during an intense workout, but be careful about sugar and additives.
- Greek yogurt with fruit, almond butter, peanut butter on whole-grain bread, or a cup of oatmeal topped with fruit and nuts are other good pre-workout foods.
- A handful of nuts paired with complex carbohydrates can be a good option before weight lifting or any type of exercise.