Does Intermittent Fasting Support Fitness Goals?


Intermittent fasting (IF) is a popular diet trend that involves cycling between periods of eating and fasting. Some people claim that IF can help them lose weight, improve their health, and enhance their performance. But is there any truth to these claims? And how does IF affect your fitness goals?

Does Intermittent Fasting Support Fitness Goals?

What is intermittent fasting?

Intermittent fasting is not a specific diet, but rather a pattern of eating. There are different types of IF, such as:

  1. 16/8 method: This involves fasting for 16 hours a day and eating within an 8-hour window, such as from noon to 8 p.m.
  2. 5:2 method: This involves eating normally for 5 days a week and restricting your calorie intake to 500-600 calories on 2 non-consecutive days.
  3. Eat-stop-eat method: This involves doing a 24-hour fast once or twice a week, such as from dinner one day to dinner the next day.
  4. Alternate-day fasting: This involves fasting every other day, either by not eating at all or by eating very little (about 25% of your normal calories).
  5. Warrior diet: This involves eating only small amounts of fruits and vegetables during the day and having a large meal at night.

The idea behind IF is that by limiting your eating window, you reduce your overall calorie intake and allow your body to use its stored fat for energy. IF may also have some benefits for your hormones, metabolism, and cellular health.

How does intermittent fasting affect your fitness goals?

The effects of IF on your fitness goals may depend on several factors, such as your current weight, body composition, activity level, and type of exercise. Here are some possible benefits and drawbacks of IF for your fitness goals:


  1. Fat loss: IF may help you burn more fat by depleting your glycogen (stored carbohydrates) and increasing your fat oxidation (breakdown of fat). One study found that people who fasted overnight and exercised in the morning burned 20% more fat than those who ate before exercise (1). Another study found that IF combined with resistance training reduced body fat and preserved muscle mass in young men (2).
  2. Insulin sensitivity: IF may improve your insulin sensitivity, which means your cells can use glucose (sugar) more efficiently for energy. This can help lower your blood sugar levels and reduce your risk of diabetes and metabolic syndrome. One review found that IF improved insulin sensitivity and glucose control in people with and without diabetes (3).
  3. Autophagy: IF may stimulate autophagy, which is a process that cleans up damaged or unwanted cells and recycles them into new ones. This can help prevent aging and disease, as well as enhance muscle growth and repair. One study found that IF and exercise increased autophagy in mice (4).


  1. Performance: IF may impair your exercise performance, especially if you are highly trained or do intense workouts. This is because fasting may reduce your energy levels, strength, endurance, and recovery. One study found that IF reduced performance and muscle power in elite cyclists. Another study found that IF decreased sprint performance and muscle glycogen in soccer players.
  2. Muscle gain: IF may make it harder to gain muscle, especially if you are not eating enough protein or calories. This is because fasting may increase muscle breakdown and decrease muscle synthesis. One study found that IF reduced muscle gain and strength in young men compared to a normal diet. Another study found that IF did not affect muscle mass or strength in older women, but also did not improve them.
  3. Hunger: IF may cause you to feel hungry, irritable, or lightheaded during your fasting periods. This may affect your mood, motivation, and concentration. IF may also increase your appetite and cravings, which may lead to overeating or bingeing during your eating periods. One study found that IF increased hunger and desire to eat in healthy adults. Another study found that IF increased binge eating behavior in women with bulimia nervosa.

How to do intermittent fasting and exercise safely ? 

If you want to try IF and exercise, here are some tips to do it safely and effectively:

  1. Choose a type of IF that suits your lifestyle and preferences: There is no one-size-fits-all approach to IF. You may need to experiment with different types of IF and see what works best for you. Some factors to consider are your daily schedule, your hunger levels, your social life, and your health conditions.
  2. Listen to your body: IF is not for everyone. Some people may experience negative side effects, such as fatigue, headaches, nausea, or low blood pressure. If you feel unwell or uncomfortable, stop fasting and consult your doctor. You may need to adjust your fasting duration, frequency, or intensity, or avoid IF altogether.
  3. Plan your workouts around your eating window: You may want to schedule your workouts during or shortly after your eating window, when you have more energy and nutrients. Alternatively, you may want to do low-intensity or moderate-intensity workouts during your fasting window, when you can burn more fat. Avoid doing high-intensity or long-duration workouts during your fasting window, as this may increase your risk of injury, dehydration, or muscle loss.
  4. Eat a balanced and nutritious diet: IF is not an excuse to eat whatever you want during your eating window. You still need to eat a balanced and nutritious diet that meets your calorie and macronutrient (protein, carbohydrate, and fat) needs. Make sure to eat enough protein to support your muscle growth and repair, and enough carbohydrates to replenish your glycogen stores. Also, eat plenty of fruits, vegetables, whole grains, nuts, seeds, and healthy fats to get your vitamins, minerals, antioxidants, and fiber.
  5. Stay hydrated: IF may cause you to lose water and electrolytes, especially if you sweat a lot during your workouts. This may lead to dehydration, which can impair your performance and health. Make sure to drink enough water and fluids throughout the day, and especially before, during, and after your workouts. You may also want to add some salt, lemon, or electrolyte supplements to your water to prevent electrolyte imbalance.


Intermittent fasting is a diet pattern that involves cycling between periods of eating and fasting. It may have some benefits for your fitness goals, such as fat loss, insulin sensitivity, and autophagy. However, it may also have some drawbacks, such as performance impairment, muscle gain difficulty, and hunger. If you want to try IF and exercise, you need to choose a type of IF that suits you, listen to your body, plan your workouts, eat a balanced diet, and stay hydrated. IF and exercise may not be suitable for everyone, so consult your doctor before starting any new diet or exercise regimen.