Why So Tired?? Energy After Weight Loss Surgery

Steph Wagner

May 20, 2015

Low Energy After Weight Loss Surgery

Why am I so tired, regaining energy after weight loss surgery. Blog article by Steph Wagner bariatric dietitian on FoodCoachMe

Getting the pep back in your step after Gastric Sleeve or Gastric Bypass

Have you had weight loss surgery and find yourself just dragging through your day?

Before having Gastric Sleeve or Gastric Bypass surgery you probably dreamed of all the energy you were going to have. Why? Because that’s what everyone says after surgery! “I have SO much more energy now!”

But what happened? Where is your energizer bunny pack?!

Energy after surgery can be related to many, many things. But yes in general…you should expect to have more energy after losing weight. So what’s going on? Why isn’t this the case for you?


The #1 most common reason for low energy after surgery is…….


You’re low on water.

Even a mild dehydration can make you feel super sluggish.

If you feel like you might be behind on water or if you’ve wondered if being low on water can slow down your weight loss, you’ll want to watch this video on Mild vs Severe Dehydration. 

We mostly think of dehydration as the time to go get IV fluids, which can happen, but mild dehydration may not be severe enough to need fluids…yet.

Post-op weight loss surgery patients ARE more prone to dehydration and not only is it best for your progress to get in 64 to 96 ounces of water, it’s also important to keep you from getting to the point of needing fluids.

If you do wonder at what point you need to get IV fluids, read this blog. 

BUT! If you feel like you’re doing fine on your fluids, let’s move on to some other options.


Another common reason for lower energy after surgery is….


You’re still in your healing phase.

Everyone recovers from surgeries in different ways. Some people are up and walking without trouble. Some people really struggle with nausea. Others are left very lethargic and sleepy.

Even if it’s been a few weeks since your surgery, don’t feel bad if you still feel low on energy. After all, you DID just have a major surgery! Get rest, get water and give yourself some time. Surgeons I’ve worked for have said the healing phase after surgery is eight weeks. If you have not reached the eight week mark, your energy may have yet to return but is on it’s way!


And another reason could be….


Your sleep schedule.

It’s easy to blame surgery for being tired but when you think about it, you haven’t really had a set routine on sleeping. Perhaps you’ve been staying up late or having patchy sleep through the night. This is a very difficult reality for many.

There are different tactics to having more success at sleeping at night including not using phones or looking at other screens before bedtime. Also, keep you bedtime consistent each night as well as your morning wakeup time.

For me, writing down the worries that are on my mind before bed help me to sleep well because I know I won’t forget what I need to do in the morning. The list will be waiting for me! Make sure to invest in this area of your life to gain the energizing benefits of losing weight.

Sleep issues are a complex thing and it does help to read books, talk to professionals, ask around for advice. Not unlike weight loss, it may take finding the right strategy for you but it does matter to keep trying.


Oh wait, here’s another one…


Over-doing it on your exercise plan.

If you’re super excited about hitting the gym but feel super exhausted throughout the day, you could be hitting it a little too hard.

When you work out at a higher heart rate (running, heavy lifting, aerobics) your body starts burning from carbohydrates instead of from stored fat. However, if you’re following a bariatric diet you probably aren’t eating much for carbohydrates. The result? You feel tired and hungry.

The best way to burn fat when exercising is to keep your heart rate lower like walking, light pool aerobics or light bike riding. Make sure you can keep a conversation when you’re working out. Metabolic testing may help you know what heart rate is best for you, although it takes a bit of research to know who offers this testing in your area.


Okay one more….



If starches or sweets are sneaking back into your diet, you could experience drastic spikes and even drops in your blood sugars (yes, even for non-diabetics) which can leave you lethargic. Sticking to lean proteins and non-starchy vegetables will keep your body burning from fat which traditionally keeps you in a great place with energy.


Wait we actually have one more thing to talk about…

Have you had your labs checked lately? 

Every bariatric surgeon is a little different on when and how often then want labs checked. Many patients are quick to think low energy is vitamin related when it is not. 

However, it’s important to have your levels check if you had surgery more than a year ago and haven’t had your labs checked in a long time.

Vitamin deficiencies can be slow to come around. In fact, sometimes lab values in a normal range feels like permission to miss some vitamins here or there.

You may want to see my blog post (and video) covering What Vitamins a Post-Op Really Needs for a review on what vitamins are recommended and for how long after surgery.

Low levels of iron, Vitamin D, B12, thiamine or others can be the reason for fatigue. In my experience, patients are run down more because of water than vitamins but it shouldn’t be ruled out especially the further you get from surgery.


There are plenty of other reasons fatigue can plague you after surgery.

For the same reasons it can before surgery! Look back at what other factors may be dragging you down. Stress? Work? Snoring spouse?

Actions Steps:


If you’re feeling run down:

Drink more water.

Consider having your labs checked if it’s been a while.

To help push through it, turn on all the lights and turn on some music.

Go for a walk.

Use different practices that tend to help perk you up, even if just for the moment.

If you have the luxury of grabbing a nap, go for it. But set a timer in your phone so it doesn’t goof up your nighttime sleep pattern. Naps are okay on occasion, but even better if you can get to the root issue and find a way to solve your “out of gas” problem.

Review which item might be the reason for your sluggishness. Then make a plan. Do you need to read a book on sleep habits? Buy a new water bottle? Give yourself more space to heal since your surgery?

Perk up buttercup! It’s a beautiful day…seize it!

– Steph

Free weight loss surgery teaching videos from bariatric dietitian. Best meal plan after surgery, the truth about carbs and how to strengthen your willpower

21 thoughts on “Why So Tired?? Energy After Weight Loss Surgery”

  1. This was very helpful! I just had the gastric sleeve 3 weeks ago and I am absolutely dragging. Thanks for the great suggestions.

  2. @Chris I’m so glad you found it helpful! Congratulations on your surgery and be kind to yourself as you heal and recover too!

  3. I had gastric bypass on 8/13/18 and so Inam quite a few weeks post-surgery. I have had three issues: severe fatigue, inability to fall asleep at my regular bedtime (sometimes for hours), and chills, punctuated by hot flashes (I am 61.). I am struggling to get enough protein in as my tummy starts to hurt. This post has helped me feel not so alone.

  4. @Rose thank you so much for your comment and so grateful to hear it’s brought you peace that you aren’t alone. Everyone’s healing journey is so unique!

  5. You left out a huge one. You aren’t getting enough vitamins and you need your blood levels checked. I just had my iron levels tank because my new body isn’t storing it properly.

  6. @Stephanie Symonds oh you’re absolutely right! I usually see the patients after they have had lab work done but certainly need to add it here. Thank you for your comment!!! Hope you feel better soon.

  7. I agree with the others regarding your thoughtfulness for us bariatric peeps! You are a wealth of knowledge and the journey is getting easier since I found you and the site! Thanks so much!!!

  8. Very helpful, made sense of the sluggish feelings I have had from time to time. A good lesson learnt on I need to be good to myself and not beat myself up for a lack of energy. Great tips.

  9. I am post op 8 months & have very low energy. I am getting about 40 ops. water in daily. This could be my issue after I read this article.

  10. Thanks so much for the tips. I had my VSG on 10/8/19. Best decision I ever made for my health. Water intake is definitely low. Hard to focus and make time for water. Just part of the journey I guess.

  11. I am so weak I cannot walk or stand maybe 20 minutes at a time. I am now taking my vitamins through iv to c if this helps. I cannot drink 16 oz of water ever after 3 1/2 mos. cannot eat anything but 5 or 6 bites of soup, a hard boiled egg and sugar free popsicles. I cannot stand the smell of food, looking at food on pic or tv. I have been in hospital once when I blacked out at hotel. Blood pressure low, dehydration, no magnesium and potassium. Noone seems to know what to do! I wish I could have the old me back! My dr says it is normal, but i am beginning to think he is crazy. Bad thing is I paid for this myself and now I am sick every day.

  12. @Connie I am SO sorry to hear it has been such a hard road!!! Yes, your symptoms sound very much related to too little water. Dehydration is a big deal after surgery! All I can do from the other side of a computer screen is encourage you to find whatever way you can to get liquid into your body! Warm broth, herbal tea, water with lemon/lime/cucumber/mint. Change up temperature or flavors…whatever you can do! Nausea is a symptom of dehydration which is a bit of a chicken or the egg when you feel too nauseous to drink. That’s the goal with IV fluids is to get you back to hydrated so you can then get on top of fluids again but when you get behind it can be extremely hard to dig back out of the hole. It will get better but not without a lot of hard work! Wishing you all my best! Steph

  13. Thanks had the sleeve 5/13/19 feel good ,but not drinking enough water this information has been very helpful. Will start drinking more water today other than that everything else is great.

  14. I had gastric bypass 2 weeks and 2 days I’m eating ok very slowly I eat nothing but vegetables and steamed pompano fish yesterday I tried broccoli big mistake I should’ve purred it I felt it got stuck which was painful after 2 hrs pain was still their I was so scared of injuring my self that I decided to go have a dumping moment which really to my surprise no pain in doing that best thing ever but we live and learn so any how I feel very very weak I drink 24 ounces of water but I will push for more and I take a nap every day straight after breakfast because I feel so weak then I sit all day on the couch until it’s night time hopefully I will feel better after 8 weeks thank you this information has helped me I was so worried

  15. Hi Belinda! I would definitely focus on water. You might be experiencing signs of dehydration so watch that you don’t need to contact your doctors office for fluids. You might need to focus on water over meals at this point with only 24 ounces of water. When you do have food make sure to keep your bites TINY, the size of a small black bean. Programs differ but I don’t add vegetables until 4 weeks after surgery and focus on tolerating protein foods well. Wishing you all the best!! !

  16. I had sleeve gastrectomy July 21, 2020. I have followed the rules and I am getting over 64 ounces of water down. My problem is weakness and hunger. 4 ounces of soft food three times a day is not satisfying my hunger or addressing my weakness I know it’s been only two weeks but I cannot believe that I’m going to have to live the rest of my life eating 3 six ounce meals a day. I have had no problems with nausea, diarrhea, or problems getting down liquid. My problem is the hunger and weakness. I do not get a full feeling or even a satisfied feeling after eating and I feel like I’m starving to death. I hope things improve. Right now I am regretting getting the surgery. My weight the day of surgery was 352 And I am currently at 328.

  17. @Jim I am sorry it has been a rough few weeks! In my experience you will feel significantly better when you can advance to the solid phase of foods. Every program is different when you can do that. I do not limit portion sizes for my patients. I have them focus on small bites, eat slowly and listen to their own body for their stopping point. If it’s a lean, solid protein and veggies (once you are are at that stage) you won’t overeat by filling up on what you need. It won’t be like this for life!!!

  18. I recently had the Rouen y gastric bypass surgery and I am drinking water every 15 minutes. Lately I have been feeling very weak every day at 400pm. Which is weird sometime sooner. Just did my blood work up today. Hope everything is good. I have no energy. I take my vitamins and even added protein shakes back in my diet I had the surgery on May 11 2021. Looking for this 8 week post surgery week to come so I can see if anything changes. Right now I just want to be back to the old me. Where I had all the energy in the world. Looking to return to the old me. Weight wise I lost about 40 pounds my first month now just need to focus on walking more and keep losing the weight. Please let me be myself again. Especially soon my son is on his last year in high school and I know he want his happy cheerful mommy back.

  19. Hi my name is april I had the gastric sleeve oct 2020 at the beginning I got dehydrated a couple of times and had to get an IV now I am 9 months out I am still struggling with water my energy was good at first now I am struggling I always feel fatigue and sluggish and I don’t know what to do I am starting to go into depression

  20. I am sorry to hear this! Struggling with water is certainly a big culprit for lack of energy. I would also recommend reaching out to your primary care doctor to review your medications and also talk about a mental health care professional if you are starting to feel symptoms of depression. Surround yourself with beverage options, keep the containers open if you can so you can stay constantly drinking!

    Here is another blog post on dehydration – https://www.bariatricfoodcoach.com/wls-patients-when-you-should-get-iv-fluids/

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