Intermittent Fasting and Exercise
Intermittent fasting is a popular health trend that involves abstaining from food for a certain period of time, followed by a period of eating. It has gained a lot of attention in recent years for its potential health benefits, including weight loss, improved insulin sensitivity, and reduced inflammation. However, many people wonder how to exercise while intermittent fasting. In this article, we will explore the science behind exercising in a fasted state, share some anecdotes from people who have tried it, and provide a step-by-step plan for exercising while intermittent fasting.
Science of exercising during intermittent fasting
The human body uses two primary sources of fuel for energy: glucose and fat. When we eat food, our body converts the carbohydrates into glucose, which is then used for energy. However, when we fast, the body starts to burn fat for energy instead. This is because when we fast, our insulin levels drop, which allows the body to access stored fat for fuel.
Exercising in a fasted state can be beneficial because it increases the body's ability to burn fat for energy. A study published in the Journal of Applied Physiology found that exercise in a fasted state increased fat oxidation, or the ability of the body to burn fat for energy, by up to 20% compared to exercising after a meal. Additionally, another study published in the British Journal of Nutrition found that exercising in a fasted state improved insulin sensitivity, which can be beneficial for people with type 2 diabetes.
However, there are some potential downsides to exercising while fasting. For example, some people may experience dizziness, fatigue, or low blood sugar levels. It is important to listen to your body and stop exercising if you feel unwell.
Anecdotes of exercising during intermittent fasting
While the science behind exercising while intermittent fasting is promising, it is important to also consider anecdotal evidence from people who have tried it themselves. Here are a few stories from people who have successfully exercised while fasting:
"I started exercising in the morning before I broke my fast, and I noticed that I had more energy and was able to complete my workouts more easily. Plus, I lost a few pounds over the course of a few weeks!" - Sarah, 35
"At first, I was hesitant to exercise while fasting because I thought I wouldn't have enough energy. But after trying it a few times, I realized that I had plenty of energy and even felt more focused during my workouts." - John, 42
"I tried exercising while fasting, but I found that it didn't work for me. I felt lightheaded and couldn't complete my workouts. However, I know that it works for other people, so I think it's just a matter of listening to your body and figuring out what works best for you." - Maria, 29
Step-by-step plan for exercising during intermittent fasting
If you are interested in trying exercising while fasting, here is a step-by-step plan to get started:
Step 1: Choose a fasting protocol
There are several different fasting protocols that you can choose from, including:
16/8 method: This involves fasting for 16 hours and eating within an 8-hour window.
5:2 method: This involves eating normally for five days and restricting calorie intake to 500-600 calories on two non-consecutive days.
Alternate day fasting: This involves alternating between days of normal eating and days of fasting.
Choose the fasting protocol that works best for you and your lifestyle.
Step 2: Choose a time to exercise
If you are doing the 16/8 method, you may want to exercise during the last few hours of your fast before breaking your fast. If you are doing alternate day fasting, you may want to exercise on your non-fasting days. Choose a time to exercise that works best for your schedule and energy levels.
Step 3: Choose your workout
Choose a workout that fits your fitness level and goals. If you are new to exercising, start with something low impact like walking or yoga. If you are more experienced, consider weightlifting, HIIT (high-intensity interval training), or cardio.
Step 4: Stay hydrated
It is important to stay hydrated while fasting and exercising. Drink plenty of water throughout the day, and consider adding electrolytes to your water to help with hydration. We recommend Fast Lyte
Step 5: Listen to your body
While exercising while fasting can be beneficial, it is important to listen to your body and stop if you feel unwell. If you feel lightheaded, dizzy, or weak, stop exercising and break your fast with a small meal or snack.
Step 6: Break your fast with a nutritious meal
After your workout, it is important to break your fast with a nutritious meal. Focus on whole foods like lean protein, vegetables, and healthy fats to help refuel your body after exercise.
Here's an example of a weekly exercise schedule for someone practicing 16/8 intermittent fasting
Monday:
8:00 AM: Wake up and begin 16-hour fast
12:00 PM: Cardio - 30 minutes of moderate-intensity cardio (such as brisk walking, cycling, or swimming)
12:30 PM: Break fast with a nutritious meal high in protein, healthy fats, and vegetables
3:00 PM: Strength Training - 30 minutes of full-body strength training (such as squats, lunges, push-ups, and rows)
5:00 PM: Break with a small snack or protein shake
7:00 PM: End feeding window and begin 16-hour fast
Tuesday:
8:00 AM: Wake up and begin 16-hour fast
2:00 PM: Break fast with a nutritious meal high in protein, healthy fats, and vegetables
4:00 PM: Cardio - 30 minutes of high-intensity interval training (HIIT) (such as sprint intervals on a treadmill, bike, or rowing machine)
4:30 PM: Break with a small snack or protein shake
7:00 PM: End feeding window and begin 16-hour fast
Wednesday:
8:00 AM: Wake up and begin 16-hour fast
12:00 PM: Strength Training - 30 minutes of upper body strength training (such as bench press, overhead press, and bicep curls)
1:00 PM: Break fast with a nutritious meal high in protein, healthy fats, and vegetables
3:00 PM: Rest or light stretching
5:00 PM: Break with a small snack or protein shake
7:00 PM: End feeding window and begin 16-hour fast
Thursday:
8:00 AM: Wake up and begin 16-hour fast
12:00 PM: Cardio - 30 minutes of low-intensity steady-state cardio (such as a slow jog, elliptical machine, or cycling)
12:30 PM: Break fast with a nutritious meal high in protein, healthy fats, and vegetables
3:00 PM: Strength Training - 30 minutes of lower body strength training (such as deadlifts, leg press, and calf raises)
5:00 PM: Break with a small snack or protein shake
7:00 PM: End feeding window and begin 16-hour fast
Friday:
8:00 AM: Wake up and begin 16-hour fast
12:00 PM: Cardio - 30 minutes of moderate-intensity cardio (such as brisk walking, cycling, or swimming)
12:30 PM: Break fast with a nutritious meal high in protein, healthy fats, and vegetables
3:00 PM: Strength Training - 30 minutes of full-body strength training (such as squats, lunges, push-ups, and rows)
5:00 PM: Break with a small snack or protein shake
7:00 PM: End feeding window and begin 16-hour fast
Saturday:
8:00 AM: Wake up and begin 16-hour fast
10:00 AM: Rest or light stretching
12:00 PM: Break fast with a nutritious meal high in protein, healthy fats, and vegetables
2:00 PM: Cardio - 30 minutes of high-intensity interval training (HIIT) (such as sprint intervals on a treadmill, bike, or rowing machine)
2:30 PM: Break with a small snack or protein shake
5:00 PM: Strength Training - 30 minutes of upper body strength training (such as bench press, overhead press, and bicep curls)
7:00 PM: End feeding window and begin 16-hour fast
Sunday:
8:00 AM: Wake up and begin 16-hour fast
10:00 AM: Break fast with a nutritious meal high in protein, healthy fats, and vegetables
12:00 PM: Cardio - 30 minutes of moderate-intensity cardio (such as brisk walking, cycling, or swimming)
12:30 PM: Break with a small snack or protein shake
3:00 PM: Strength Training - 30 minutes of lower body strength training (such as deadlifts, leg press, and calf raises)
5:00 PM: Break with a small snack or protein shake
7:00 PM: End feeding window and begin 16-hour fast
This exercise regime includes both strength and cardio training, alternating between the two throughout the week. The feeding window is adjusted to include meals around the workout times to ensure adequate fuel and recovery. We mention electrolytes and protein shakes, which are by no means essential. However, if you would like to optimise your health regime, we recommend the following:
Electrolytes for rest days - Fast Lyte
Electrolytes/pre workout - Optimum Nutrition Amino Energy
Protein powder - Optimum Nutrition Gold Standard
Conclusion
Exercising while intermittent fasting can be a beneficial way to improve fat oxidation and insulin sensitivity. However, it is important to listen to your body and stop if you feel unwell. If you are interested in trying exercising while fasting, follow these steps: choose a fasting protocol, choose a time to exercise, choose your workout, stay hydrated, listen to your body, and break your fast with a nutritious meal. As with any new exercise or dietary program, it is important to consult with a healthcare professional before starting.
Studies mentioned in this article
Van Proeyen K, et al. (2011). Beneficial metabolic adaptations due to endurance exercise training in the fasted state. Journal of Applied Physiology, 110(1), 236-245. DOI: 10.1152/japplphysiol.00995.2010
De Bock K, et al. (2012). Exercise in the fasted state facilitates fibre type-specific intramyocellular lipid breakdown and stimulates glycogen resynthesis in humans. The Journal of Physiology, 590(2), 435-446. DOI: 10.1113/jphysiol.2011.219911
Arnason T, et al. (2017). Effects of intermittent fasting on health markers in those with type 2 diabetes: A pilot study. Journal of Nutritional Therapeutics, 6(2), 43-56. DOI: 10.6000/1929-5634.2017.06.02.1