Is it Bad to Work Out on a Full Stomach?

by Janet Renee, MS, RD; Updated April 11, 2018

Planning and timing your meals plays a central role in fueling muscles during a workout and recovering after a workout. Food fuels exercise, whether you're strength training or engaging in aerobics. Conventional wisdom suggests waiting at least an hour after eating before exercise, particularly rigorous exercise. Allowing your meal to digest helps fuel your muscles as you exercise. It also helps prevent complications such as gastrointestinal problems, fatigue and compromised digestion.

One Thing at a Time

When you eat, the smooth muscles of your digestive system get to work digesting food. For your body to digest nutrients, your body must break the food down into smaller, easy to absorb units. To complete this job, a significant portion of blood flow is diverted to your digestive system. If you work out on a full stomach, without giving your meal time to digest, some of the blood flow is then directed to your working muscles, which compromises digestion.

An Eye on Performance

Your body typically sends blood to your working muscles as you exercise. When your digestive system and your working muscles are both in competition for blood supply, neither can perform optimally. This means you won't get the most out of your workout, since digestion is impinging on some of the blood supply. If you're performing strength training exercises, you may find you aren't able to lift as heavy or complete as many reps. If you're doing aerobics, you may become exhausted sooner than usual.

Easy on the Stomach

Exercising on a full stomach increases the risk of experiencing digestive upset. Exercising during digestion can lead to nausea, stomach cramps or even vomiting. As your body goes about the business of digestion, stomach acids help break down food. Exercising can cause stomach acids and food particles to enter the esophagus, causing heartburn. You may start to feel bloated or have an uncomfortable sensation in your stomach, which reduces your ability to exercise.

Meal Timing

Time your meals to allow an hour to digest your food before exercising. Avoid eating too much before exercise. You want the food to empty from your stomach into your small intestines, where your body can absorb nutrients to help fuel you as you work out. Eating a large meal tends to delay gastric emptying, which means your body won't get optimal nutrition prior to exercise. Eating a small meal of complex carbohydrates, such as oatmeal, helps provide the necessary fuel.

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