What Causes Weight Gain After Surgery?

Surgery can be an overwhelming and nerve-wracking experience.

Taking new medications, handling pain and discomfort, and even noticing changes in your body, such as weight gain, can all make recovery a challenging process.

While your priority should always be to rest and recover, you may wonder why you see extra weight on the scale and whether it’s something you should be concerned about.

This article reviews weight gain after surgery, its main causes, and helpful tips to prevent it.

Is weight gain common after surgery?

Surgery is usually a highly invasive procedure that takes a toll on your body as it works overtime to promote healing. Depending on the type of surgery you have, your recovery may be a short or lengthy process.

In some cases, you may experience some weight gain after surgery as a result of fluid retention, a side effect of medication, or being sedentary for a long time. However, this depends on the type of surgery, the expected recovery time, and your medical history (1, 2).

Weight gain during the initial recovery period is usually not a result of gaining fat mass but rather an accumulation of fluid as part of the healing process. In most cases, postsurgical weight gain is temporary and subsides as your body recovers.

However, prolonged recovery time, physical inactivity, stress, and changes in your eating behavior can lead to weight gain over time. Therefore, it’s important to try to resume your usual healthy lifestyle as soon as it is safe to do so.

While usually temporary, postsurgery weight gain can occur in people who have excess fluid buildup and swelling. Physical inactivity, stress, and changes in eating habits can also lead to weight gain, depending on the length of your recovery time.

Causes of weight gain

There are many potential causes of weight gain after surgery.

Fluid retention

The most common cause of weight gain after surgery is fluid retention, also known as postoperative edema.

Edema occurs when extra fluid builds up in your body to respond to inflammation and promote healing. It may also be caused by intravenous (IV) fluids given during surgery. Edema can be localized (in one spot) or generalized (throughout your body) (3, 4).

Common symptoms of edema include puffiness, swelling, decreased mobility at the joints (e.g., fingers, ankles, wrists), decreased urine output, and rapid weight gain (3, 4).

Though it usually subsides on its own, in some cases, your surgeon may recommend a prescription diuretic to reduce swelling or adjust other medications you’re taking that may promote edema, such as corticosteroids or calcium-channel blockers (3).

They may also suggest wearing compression clothing, engaging in gentle movement, reducing salt intake, and elevating the affected area. If you have concerns about swelling and edema, it’s best to talk with your surgeon or another medical professional (3).

Being sedentary

Depending on the type of surgery you have, you may need to limit your physical activity for days to weeks afterward.

Though a few days of rest won’t cause substantial weight gain, prolonged sitting paired with physical inactivity for extended periods of time can lead to a decrease in muscle mass and daily calorie expenditure. As a result, your fat mass may increase (5).

Fortunately, rehabilitation is a large component of postsurgical care. It includes seeing specialists such as physiotherapists and occupational therapists, who can help you return to your normal activities and reduce muscle wasting (6, 7).

If you had a minor surgery with a short recovery time, allow yourself to rest before slowly reintroducing your usual physical activities. After a major surgery, you may need to rest for an extended period before resuming exercise.

Once you can safely resume exercise, slowly reintroduce gentle movement, such as walking or yoga, to see how you feel and tolerate it. You may need to gradually reintroduce straining activities, such as lifting weights, or avoid them until you’re fully recovered.

Though it may be tempting to return to your normal fitness routine once you start feeling better, be sure to speak with your doctor and receive medical clearance first.

Comfort food

Recovering from surgery can be painful, stressful, and emotionally draining. This may have you reaching for your favorite comfort food to help you cope.

However, if you continue to rely on comfort food rather than return to a more balanced diet after you’ve recovered, you may experience weight gain over time.

During your initial recovery, it’s important to focus on consuming enough calories and protein to promote recovery, even if you can tolerate only certain foods, such as ice cream, pudding, Jell-O, or scrambled eggs (8, 9).

Depending on your surgery and preoperative nutrition status, you may work closely with a registered dietitian as part of your postoperative care.

They may recommend a therapeutic diet, such as liquids only, or additional supplements, such as protein or energy shakes, to support your recovery (8).

However, as you regain your appetite and ability to eat, focus on reintroducing foods high in protein to support healing and prevent muscle loss. Further, eating high fiber foods will help promote bowel regularity and reduce constipation, which is common after surgery (8).

If you’re hungry between meals, try eating small snacks that contain protein and fiber — such as peanut butter and apple slices — which will keep you satisfied and full.

Additionally, try to stick with low calorie drinks like water, coffee, and tea instead of sugary beverages or alcohol.

It’s OK to enjoy comfort foods as part of your recovery. Allow yourself the flexibility to eat foods that feel good for you in the moment. However, if you begin to use food or alcohol as a regular coping mechanism, speak with a dietitian or medical professional.

Edema, or fluid accumulation, can lead to weight gain that will go down as you recover. Inactivity and comfort eating may also contribute to body fat gain. To minimize weight gain, try to resume regular physical activity and healthy eating once you’ve recovered.

A word on weight gain

Undergoing surgery is not a small feat. It takes courage and strength to heal both physically and mentally.

Although you may notice changes in the size of your body, it’s important to remember that your body has gone through tremendous stress and needs time to heal.

Instead of focusing on the number on the scale, focus on your body’s amazing ability to heal itself. Be patient with your recovery and slowly reintroduce your previous healthy habits when your body is ready.

Having a healthy recovery from surgery — not the number on the scale — should be your main priority. If you have concerns about sudden or gradual weight gain, speak with a medical professional.

The bottom line

Having surgery can be a stressful and life-changing experience. On top of focusing on a healthy recovery, you may be worried about changes to your body, such as weight gain.

Sudden increases in weight are likely temporary and due to a buildup of excess fluid, which is common after major surgery. In some cases, a lengthy recovery may require you to be less active, which can lead to weight gain.

While it’s important to work toward a physically active lifestyle and healthful diet, it may take time before your body is ready to return to your usual activities. Remember that your body is in recovery mode and it’s important to be patient with this process.

Working closely with your doctor will help ensure you have a safe and healthy recovery, which is always more important than the number on the scale.