I. Exercises to Avoid on an Empty Stomach

High-Intensity Interval Training (HIIT)
HIIT entails short bursts of intense exercise followed by brief recovery intervals. It demands a considerable amount of energy within a short period. When you are fasting, your blood sugar levels are low. Without an adequate supply of glucose from food, your body might struggle to furnish the energy required for such intense activity. This can result in dizziness, light-headedness, and a lack of endurance. For instance, a HIIT session that incorporates sprints and burpees can rapidly deplete the limited energy reserves in your body when you have not eaten, making it challenging to complete the workout effectively and increasing the risk of fainting.

Long-Distance Running
Long-distance running necessitates a continuous supply of energy. When running for an extended period, your body primarily utilizes glycogen stored in the muscles and liver as fuel. If you commence a long-distance run on an empty stomach, you may “hit the wall” sooner. This implies that your glycogen stores are depleted, and your body has to rely on fat metabolism, which is a less efficient energy-providing process during exercise. As a consequence, you will experience extreme fatigue, a significant reduction in pace, and may even have to halt the run prematurely. For example, a marathon runner who starts the race without consuming enough beforehand may find it nearly impossible to maintain a good running rhythm and complete the race.

Heavy Weightlifting
Weightlifting, especially heavy-duty sessions, requires a great deal of energy. Your muscles need fuel to contract and lift the weights. When you are empty-stomached, your body may not have sufficient glycogen to support the intense muscle contractions. This can lead to muscle weakness and an augmented risk of injury. Additionally, low blood sugar can cause shakiness, which is not conducive to maintaining proper form during weightlifting. For example, attempting to bench-press a heavy weight without any prior food intake might lead to a lack of strength to complete the lift and a higher likelihood of dropping the weight or straining a muscle.

II. Exercises to Avoid on a Full Stomach

High-Impact Aerobics
High-impact aerobic exercises such as jumping jacks, plyometric jumps, and high-knee running involve a great deal of bouncing and jarring movements. When your stomach is full, these movements can cause discomfort, nausea, and even vomiting. The food in your stomach can slosh around due to the intense up-and-down or side-to-side motions, exerting pressure on the stomach walls and the esophageal sphincter. For example, if you engage in a high-impact aerobic class immediately after a large meal, you may feel a queasy stomach and have to stop the exercise to avoid getting sick.

Inverted Yoga Poses
Inverted yoga poses like headstands and shoulder stands require you to be upside-down. When you have a full stomach, these poses can cause the food to move in the wrong direction. Gravity can push the food back up the esophagus, leading to acid reflux and heartburn. The pressure on the abdomen in these inverted positions can also cause abdominal discomfort and a feeling of fullness or even pain. For instance, if you attempt a headstand shortly after a meal, you might experience a burning sensation in your chest due to the acid reflux.

Abdominal Crunches and Twists
When your stomach is full, performing abdominal crunches and twists can exert excessive pressure on the digestive system. The squeezing and contracting of the abdominal muscles can disrupt the normal digestion process and cause indigestion, bloating, and discomfort. For example, doing a set of intense abdominal crunches right after a large meal might make you feel overly full and uncomfortable, and it can also slow down the digestion of the food you just ate.

In general, it is essential to find a balance and select the appropriate time to exercise in relation to your meals. If you wish to exercise on an empty stomach, it is advisable to have a small snack like a banana or a handful of nuts to provide some energy. And if you have had a big meal, it is best to wait at least an hour or two before engaging in intense physical activity.