Feeling bloated after a workout can be discouraging, but there is usually a simple explanation. Most bloating is caused by a relative lack of sodium in the body — a condition known as hyponatremia according to Mayo Clinic— which leads to water retention.
Other causes can include diet, prescription medications and, in rare cases, an underlying medical disorder. Bloating can usually be easily prevented and treated, but if you start to experience other symptoms along with the bloating, such as dizziness, pain, fatigue or weakness, contact a physician immediately.
Water Retention and Bloating
The amount of sodium in your body has to be in the right proportion to the amount of blood plasma. If you are dehydrated, overhydrated or otherwise have relatively low levels of sodium, your body starts to get out of balance and bloating can result. Dehydration is a common cause when exercising; with dehydration both the levels of sodium and water are low, and you will stop sweating to conserve water.
Drinking too much water before, during and after exercise can lead to overhydration, especially in endurance athletes, which leads to bloating because your body is saturated with fluids, and your sodium levels are relatively low. Many people who are just starting to work out retain water because the body is not used to it and is in a mild state of shock. In this case, the body conserves fluids to prepare for possible future loss.
Medications and Retaining Water
Certain medications, such as anti-depressants and pain control pills, can make you sweat or urinate more. Your body reacts by retaining as much water as possible, leading to a bloated feeling, especially after a workout. Some medications can also increase your appetite, which can be a contributing factor to feeling bloated. Birth control pills that are high in estrogen often lead to weight gain in the form of water retention. Talk with your doctor if you are on any prescription medications or are taking other pills or supplements.
Diet and Appetite
What and how much you eat can lead to bloating. When you begin an exercise program, your appetite increases. Many people easily resort to overeating when this happens, thinking that they will easily burn the calories off when exercising, and gain weight. Eating right before exercising can also lead to a bloated feeling.
Intolerance to certain foods, especially milk products, can lead to digestive issues that cause bloating, and it can be exacerbated during exercise. Consuming excessive amounts of fiber can also lead to bloating says A Healthier Michigan. Eating a small meal no sooner than 30 minutes before exercising can help avoid bloating from overeating. Eat large meals at least two hours before exercising. Monitor your eating habits to see if you have any reactions to certain foods.
Dehydration and Overhydration
For the common causes of dehydration and overhydration, drinking when you are thirsty and consuming sports drinks with added electrolytes can help, both before and after exercising. Consuming small snacks high in sodium, such as pretzels and chips, before exercise can also help.
If you have white marks on your clothes or have a bitter or salty taste when you sweat, you could be a "salty sweater" according to the Victorian Institute of Sport, which means you lose more sodium than most people when you sweat. Consuming the higher-sodium snacks before, during and after exercise can help. However, it's best to consult with physician before increasing your sodium levels because high levels of sodium can lead to high blood pressure or other problems.
Body Imbalances and Bloating
Although not as common, certain medical conditions can lead to water retention and bloating. Hyperthyrodism, gastrointestinal issues, PMS and some endocrine disorders can cause imbalances in the body that lead to water retention. Consult a doctor if you have other symptoms along with bloating or if the bloating feeling is not associated with exercise.