Corticosteroid injections are widely used for their powerful anti-inflammatory effects, commonly administered to treat pain, inflammation, or allergies. These medications, such as cortisone or prednisone, are different from the anabolic steroids used to build muscle mass. Concerns about weight gain are valid, as long-term or high-dose use of corticosteroids is known to alter metabolism and cause weight changes in up to 70% of people. However, the effect of a single, localized injection on body weight is significantly different from the effects of a long course of oral tablets.
Likelihood of Systemic Side Effects from a Single Injection
A single, localized corticosteroid injection, such as one given into a joint or soft tissue, delivers a high concentration of the drug directly to the problem area. This localized approach minimizes systemic absorption into the bloodstream, which is the primary factor causing widespread side effects like weight gain. Therefore, a one-time injection is far less likely to cause a significant, lasting weight increase compared to chronic, high-dose exposure from oral steroids.
Even with a localized injection, some corticosteroid inevitably enters the systemic circulation. The potential for weight gain depends on the total dose, the specific type of corticosteroid used, and the injection site. Certain long-acting preparations, known as depot formulations, release the drug slowly and can remain active in the system for a few weeks.
Epidural steroid injections, for example, may result in greater systemic absorption than a small joint injection, increasing the chance of temporary side effects. While most single injections do not result in noticeable weight gain, the drug can cause temporary effects like fluid retention as it passes through the body. The most significant risk of weight gain comes from cumulative exposure, such as receiving multiple injections over a short period.
How Corticosteroids Influence Body Weight
Corticosteroids influence body weight by acting as synthetic versions of the natural hormone cortisol. These drugs interact with the body’s metabolism and chemistry in three primary ways that can contribute to weight gain. The first is a temporary increase in appetite, which can lead to a greater calorie intake if not consciously managed.
Corticosteroids also alter the body’s electrolyte and water balance, often resulting in temporary fluid retention. This short-term weight fluctuation is caused by the body retaining excess sodium and water, manifesting as bloating or swelling. This fluid retention is typically one of the first and most transient forms of weight increase experienced after exposure.
Furthermore, corticosteroids influence how the body handles and stores energy substrates like carbohydrates, fats, and proteins. They mimic cortisol, which promotes the storage of fat, particularly in the face, neck, and abdomen. While this fat redistribution is a hallmark of long-term, high-dose use, a single injection may cause a minor, temporary metabolic shift that supports increased fat storage.
Duration and Management of Weight Changes
Any weight gain experienced after a single corticosteroid injection is typically transient and resolves once the medication is fully processed. The steroid’s action from a localized injection usually lasts between 8 to 14 days, and the drug is expected to be fully excreted within four to six weeks. This short duration means the drug does not remain in the system long enough to cause the significant, permanent metabolic changes associated with long-term therapy.
If temporary fluid retention occurs, managing sodium intake and ensuring adequate water consumption helps the body re-establish its electrolyte balance. Reducing dietary sodium encourages the kidneys to excrete excess fluid, quickly alleviating temporary weight gain and bloating. For the temporary increase in appetite, focusing on high-fiber, low-calorie foods promotes satiety without increasing overall caloric intake.
Patients can choose healthy proteins, fruits, and vegetables to satisfy the increased hunger signal. Monitoring weight and reporting persistent concerns to the prescribing physician is advisable, particularly if perceived weight changes last beyond the expected four to six weeks. The weight gained from short-term or single-dose steroid use is generally lost as the body readjusts to its normal hormonal state.