Nutrition and surgery: How much should you eat after surgery?

Posted on July 20, 2018

(Last Updated On: July 20, 2018)

Preface: Don’t underestimate this. I know plenty of people who have gained upwards of 60 pounds after a surgery. Some of them have trouble getting this weight off years later. In fact, I know one person who for nearly 70 years (!!!) had the same waist size. After a foot surgery he gained 60 pounds and now years later has 30-40 of those pounds still on him.

Being depressed after surgery is common too. Especially with a surgery that leaves you immobile. Adding a crapload of weight, weight that is nearly all fat, only adds to this depression…




With my recent ACL procedure I’ve been looking at all aspects of surgery. From the preoperative phase to the rehab phase, picking a surgeon, any and everything related to making sure I set myself up for a successful operation.

Eventually I found myself at a rather basic question, how should you eat after surgery? Namely, do your calorie requirements go up due to all the healing your body has to do after an operation? In my ACL surgery, part of my hamstring was cut off, I had bone drilled through, and my meniscus was stitched together. It takes nutrients to help heal these injuries. I want to make sure I’m getting enough of these nutrients to promote healing, but not unnecessarily eating too much. I think we all know of someone who gained an inordinate amount of weight after a surgery.  Something that doesn’t help recovery.

To say this is a scarce area of information is an understatement. I found exactly one, apparently credible, source of information regarding caloric needs after an orthopedic procedure.  Adding to the trouble- this paper is 40 years old and references papers even older than that. It also uses some extremely small sample sizes. Never a good thing.

Nevertheless, even if the specific numbers are off, I think it gives some solid principles for how to eat after surgery.

The studies look at this by examining how much oxygen people consume before and after an operation. The logic being the more oxygen you consume the more calories you burn. E.g. You breathe harder running on a treadmill than you do walking. Ergo you burn more calories running on a treadmill than you do walking.

These studies find it’s pretty clear people consume more oxygen after a surgery than before. I don’t think this will shock anyone. After a procedure you are going to be breathing a bit harder after all the crap that was just done to your body. It’s akin to spraining your ankle. All your senses are heightened and you breathe harder due to trying to deal with the injury.

Relative to before surgery people consume about 10-20% more oxygen afterwards.  So, just eat 10-20% more than normal then? Not quite.

There are a multitude of factors that affect how many calories you burn in a day. You may be consuming 10-20% more calories at rest than normal, but after a surgery most people aren’t as active as normal. Thus, they don’t burn as many calories from moving around as they normally would.

Now this is going to be highly dependent on the person. Some people are completely sedentary as it is, thus, they really aren’t going to be much less active after surgery than before. Others are going to be dramatically less active. Using my surgery: Most people who tear their ACL are very active people. After a surgery their activity levels are going to take a huge dive.

The type of surgery affects the amount of calories burned too. If your arm is in a cast you might not decrease your activity at all. Your leg in a cast though, that’s a different matter.

As far as how long the increased oxygen consumption lasts, there’s no magic number. It’s highly dependent on the type of surgery and the type of injury.  In one group who had menisectomies there was an increased oxygen consumption most prominent in the 10 days following surgery. Normal rates didn’t return until nearly 3 weeks. In terms of your metabolism, it seems the body takes at least a couple of weeks to really recover from an orthopedic procedure.

You still need to adjust based on how active you are. A good rule of thumb is your Bodyweight x 15 = How many calories you burn each day working an average desk job. Remember, this is an average, it’s not perfect.

So, 200 x 15 = 3000 calories per day to maintain your current weight.  Adding 10% from the surgery would put us at 3300. But, we’re not as active. If we work a desk job let’s say we’re 10% less active -somebody is going to the water cooler for you- that would bring us back down to 3000.

Basically, eating to maintain your weight seems to be a good starting point for most people, for roughly 14 days after surgery.

I’ll tell you for someone like me, I knew I wasn’t going to be that less active after my surgery. I was going to be doing various exercises and I was going to be on my crutches a fair amount. Try being on crutches on one leg for an hour, it is work. Therefore, I added 20% to my daily calorie needs just to be safe I was consuming enough. From days 2-14 I brought this down to 10%. I’d rather potentially gain a pound or two in the two weeks after surgery and know I have enough calories for my leg than risk not having enough.  (Notice I said a pound or two. Not twenty.)

The overriding theme of this is don’t go to either extreme. Don’t think that because you just had surgery you can eat whatever you want, “I need my nutrients, bro,” or “Waaa I’m hurt, let me eat my sadness.” You are only making life harder for yourself. On the other end, don’t eat like a bird either.

Next, the type of calories you should be eating. Not surprisingly, after surgery carb use goes way down in exchange for fat use. This makes sense as carbs are used more for dynamic activity whereas fat is burned most when you’re just lying around. Typical of those after a surgery. It makes sense to substitute some of the carbs in your diet for some fat in the couple weeks after a procedure.

From the paper “Calorie requirements after an operation.”

This will also depend on the person though. If you’re fairly active after your surgery you are still going to be burning some carbs. Again, using me as an example, there are some days in the immediate 14 days after my surgery I was on my crutches for a few hours each day. That’s a good amount of work. Which warrants eating some carbs.

Don’t overthink this. If you’re doing nothing after your surgery, don’t eat more than you normally would; try and maintain your weight, and eat more fat than carbs. If you’re still fairly active, eat a little bit more calories and make sure you’re still eating some carbs. The end.

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