Nutrition and exercise are two of the most important factors for our overall health. Proper nutrition can fuel your workout and help your body recover and adapt. Your body’s primary sources of fuel are body fat and carbohydrates. When exercising on an empty stomach, more of your body’s energy needs are met by the breakdown of body fat. A study in
273 participants found that fat burning was higher during fasted exercise,
while glucose and insulin levels were higher during non-fasted exercise.
Not Eating Before Short-Duration Exercise May Not Affect Performance
Many people who want to perform at their best wonder if exercising fasted will harm their performance. The majority of research showed no difference in performance between those who ate before aerobic exercise lasting less than an hour and those who did not. Other studies examining high-intensity interval training (HIIT) also found no difference in performance between fasted and fed exercise. But, some studies have shown an improvement when carbohydrate-containing meals or supplements were consumed before exercise. The majority of studies do not show a clear benefit to eating before short-duration aerobic exercise or intermittent exercise like HIIT.
Eating Before Long-Duration Exercise May Improve Performance
A large analysis of exercise lasting longer than one hour found that 54% of studies reported better performance when food was consumed before exercise. Consuming slower-digesting carbs or eating several hours before exercise may benefit long-duration performance. For endurance athletes, other research has shown the benefits of eating a high-carb meal three to four hours before exercise. Overall, there is stronger evidence in support of the benefits of eating before longer-duration exercise, compared to shorter-duration exercise.
Eating After Exercise Important If You Work Out Fasted
If you eat during the several hours before you work out, the nutrients you ingest may still be present in high concentrations in your blood during and after exercise. In this case, these nutrients can aid recovery. However, if you choose to exercise fast, your body has fuelled your workout using its energy stores. What’s more, limited nutrients are available for recovery. In this case, it is particularly important that you eat something relatively soon after exercise.
One study examined whether eating a meal containing protein and carbs after fasted exercise led to greater increases in the production of proteins in your body, compared to when no nutrients were consumed. While there was no difference in how much new protein the body made, eating after exercise did reduce the amount of protein breakdown.
Personal Preference Should Be the Determining Factor
While studies have illuminated the effects of eating or fasting before exercise, the most important factor may be personal preference. Eating before exercise may be more important for particular groups, such as high-level athletes and those performing the long-duration exercise. Thus, your personal preference for when you eat relative to exercise should play the biggest role in your decision. For some people, eating soon before exercise can make them feel sluggish or nauseous. Others feel weak and fatigued without having something to eat before working out. The less time you have between eating and exercise, the smaller the pre-exercise meal should be. This can help prevent feelings of fullness and discomfort during exercise.
Although exercising without eating first can increase your body’s ability to use fat for fuel, this does not necessarily translate into greater body fat loss. In terms of performance,
there is limited support for the importance of eating before short-duration exercise. Eating before longer duration activities may be more beneficial. Eating before exercise may also be more important for high-level athletes who do not want to risk compromising their performance. While you don’t have to eat before working out, getting nutrients in the hours around exercise is important. Therefore, if you don’t eat before you exercise, try to eat soon after you exercise. Overall, personal preference should be the main factor when deciding whether or not to eat before working out.
In the next article, we will share the types of food that you should consume before and after exercise. Stay tuned! Top of Form
2. The American Journal of Clinical Nutrition, Volume 54, Issue 5, November 1991, Pages 866–870