So, you had your bariatric operation 3 weeks ago. For the first 2 weeks the weight loss was awesome, and it was SO EASY! You could get on the scale multiple times in a day, and the weight would be lower every time. In that first two weeks you may have lost 15-25 pounds, or even more. What fun!
Now we’re in week 3, and… That. Damned. Scale. Is. Not. Budging. For a lot of patients, the scale can remain stuck for a week or more. This can feel soul-crushing, as a reminder of all those times you’ve gotten stuck before. Then, everyone starts to lose again, steadily now but not as fast as before.
So what gives with the three-week weight loss stall? It’s notorious, like the hidden reefs that used to tear the bottoms out of old sailing ships. The good news is that we can make sense out of the physiology behind this stage, and also that the three-week stall does not have any negative implications for your overall weight loss. And, just as modern mariners avoid the ‘hidden’ reefs, we can use our knowledge to navigate through those treacherous waters with no (emotional) damage!
The Big Picture – Weight loss trajectory in the first year after bariatric surgery
We’re going to come back to the three-week stall by taking a look at the entire first year of weight loss first, then by zooming in on some key segments of that overall trajectory.

Weight loss trajectory in the first year after bariatric surgery
This graph has a lot of information. The curve represents fairly typical weight loss for a bariatric surgery patient (either Gastric Bypass or Sleeve) during the first year after surgery. Notice that the weight loss is brisk in the first 3 months, still steady in the second 3 months, then slow for about 6 more months. Most patients settle at a new baseline weight 10-14 months after their surgery.
Notice that we do not hope to get most patients down to the widespread reference point called “Ideal Body Weight;” this weight is actually too skinny for lasting health, once a person has carried massive excess weight. A very healthy weight range is a Body Mass Index (BMI) from 25-30. If a patient begins at a BMI over 55 then they’ll be very healthy at a BMI less than 35.
The Three-week stall
Of course, the big-picture curve is over-simplified and there’s a lot going on if we zoom in on some of the key segments. For example, if we zoom our graph into that first couple of weeks of weight loss it could look like this:

Rapid weight loss in the first two weeks
That looks like fun, right? And it is fun, as long as it lasts. The problem is, there’s a harsh flattening of that weight loss curve, ie a weight loss stall, in store for many bariatric patients. The next week or so can look something like this:

Typical weight loss pattern
The weight loss stops for a lot of patients, then seemingly for no reason the weight begins to come off again.
This whole process can be exhilarating, then frustrating, but it’s no mystery. During the first two weeks our patients do burn a lot of fat because they are eating almost nothing, but about 2/3 of the weight loss is actually from shedding water. In fact, at the end of that rapid weight loss phase most patients are a bit dehydrated as a side effect of this water shedding (even if they are drinking all the recommended fluids). Then during the 3rd week, the body “catches up” on its fluid balance. The daily increase in water during these few days leads to a frustrating weight loss stall, even though there is still some serious fat burning happening. Once the body catches up on fluid, the weight begins to come down at a more steady pace that actually does represent fat loss.
Check this little box section if you want some of the science and math behind the 3-week stall.
Science and Math behind the 3-week stall:
- How we know that a lot of the initial weight loss is water weight:
First fact – each pound of fat contains about 3,500 calories.
Second fact – patients burn 1,200-1,800 calories per day, so even with 0 calorie intake no one can burn a pound of fat in a day.
Third fact – many patients lose 2+ pounds per day during the first 2 weeks. Physiology says a lot of that weight loss must be water. - Why do patients shed so much water during those first 2 weeks? There are two mechanisms that we know of:
- Consuming glycogen – glycogen is the body’s quick-reaction energy supply. It’s stored mostly in the liver and also distributed in muscle tissues. Each gram of glycogen in the tissues is “tied up” with several grams of water. When the body notices no energy intake, before it even draws on the fat stores, it burns up the available glycogen and the “bound” water from the glycogen goes out in the urine. This is probably a less important factor because most patients probably burn up most of their glycogen during the 1-week pre-op diet, and because the total amount of glycogen for most humans is 500 grams, so that weight loss plus the fluid loss adds up only to about 2 kilograms.
- Ketosis – when the body begins to burn fat as its main fuel, one sign of the aggressive fat burning is called “ketosis.” There is a lot happening in ketosis, but the key thing for this discussion is that the ketones themselves and some of the other chemicals produced cause diuresis, which is a medical term for a situation when your kidneys are pushed to put out more urine than they normally would. During the first two weeks after bariatric surgery, many patients put out a lot of extra urine, and they become dehydrated even though they are drinking plenty of fluid. Becoming a bit dehydrated can lead to a profound sense of fatigue, and on Keto-diet websites this phase is known as the “keto flu.”
So, the body is temporarily out of balance during the rapid weight loss of the first two weeks, and the “3-week weight loss stall” is actually the body getting back into a more sustainable balance. The body rebuilds some glycogen (this is a healthy resource, with its associated water), and more importantly the diuretic effect of the ketosis begins to fade as patients naturally begin to eat a little bit of food.
What to do (and what not to do) if you get slapped with the 3-week weight loss stall:
- Keep drinking plenty of fluids! You may want to add some salty fluids such as broths, because the salts help your body keep up on hydration.
- Eat food (or don’t) according to the instructions that your surgeon and the bariatric team have given you. Eating more or eating less is not going to break the stall – your body just needs to work through this stage. Your bariatric team is thinking “long term,” and you should think that way too. Your food instructions are designed to give you the best chance of a low sustainable weight.
- Try not to compare yourself with other patients. Weight loss from fluid shifts is highly variable, and the pace of weight loss at this early stage is not a good measure of whether you’re doing a “good job” or not.
- Start to weigh less frequently. Yes, it was fun to weigh multiple times per day. But after that first two weeks the weight loss continues at a more deliberate pace. Work toward weighing yourself once a week, but also DO weigh regularly so you can keep track of your weight over the years.
Status check – three months
Most patients feel really good at this stage, and they’re losing weight steadily. It turns out that the amount of weight a patient loses from surgery up to this point in time is roughly half of the weight they will have lost when their weight reaches its lowest point. In other words, this is a great time to assess your progress. If the projected weight loss looks good, then rock on! If it looks like you’re on track to come in at some level above your goal, this is the time to work with your team to steepen the weight loss “trajectory” by intensifying habits or by intensifying medical treatment.
What to do at the 3-month status check:
- Keep the appointment with your Bariatric Team
- Discuss your weight loss goals, and discuss whether you are on track to achieve those goals. Keep an open mind about the weight loss goal – our experience is that a BMI less than about 25 is actually too skinny for most patients. Depending on where you started, a BMI from 25 up to maybe 33 is likely to be more comfortable/sustainable/healthy.
- If you and your Bariatric Team agree you are off track, then work out a plan to steepen the trajectory of your weight loss. Your team has a lot of options to help boost the surgical weight loss, and specific plans will depend on your circumstances.
Plateau time – 6 months and onward
Most patients have lost a lot of weight and many are already in a healthy/sustainable weight zone. The next 4-8 months will probably bring further weight loss, but it will be slower and less predictable. Your weight will often sit at one level for 1-4 weeks (we call that a “plateau”), then almost mysteriously drop by a few pounds over a couple of days. Even though the scale doesn’t move much during this later stage, the shape of the body continues to improve and patients very commonly report continued downsizing of clothes.
It’s natural for the “strength” of your bariatric operation to fade a little bit around this time. It’s common for patients to feel a bit more food capacity at mealtime, and to feel just a bit more hunger. These changes do not mean that your surgery is “broken,” just that your surgical anatomy continues to heal and to gradually handle food a bit more effectively than before.
At this stage, you’re making the transition from a time when your bariatric surgery controlled your weight trajectory to the rest of your life in which you keep yourself in a healthy metabolic balance. This is a great time to take stock of the healthy habits that you’ve built, and some that may still be goals of yours. With a reasonable level of conscious attention, it should feel natural to stay in control of your metabolism for decades to come.
There are two big goals at the 6-month transition, which fortunately reinforce each other:
- Keep losing weight, to the lowest healthy level that is practical
- Lock in habits that will lead to lifetime metabolic health and weight maintenance
Patients have the best success with these goals when they reinforce core guidelines, and when they monitor results regularly in the long run.
Reinforcing core guidelines:
- Choose healthy food. This means minimal carbs, and “clean” natural food that has minimal chemicals such as preservatives and all sweeteners. Food is not just calories, but it is hormonally active in your body. Healthy food tends to lead to lasting satiety and to good energy levels, but carbs or chemicals will cause increased hunger with decreased energy.
- Hydrate well, but separate liquids from your meals.
- Exercise regularly. At least 4 times per week. Any type of exercise is helpful, but it seems that strength exercise is more effective than cardio for weight control.
- Take the recommended supplements, and stay engaged with your bariatric team in the long run.
Self-monitoring:
- Journal regularly. Start with a deep/extensive description of your habits at this 6-month landmark. Make notes about your usual food, usual exercise, and also about your goals as well as your feelings about how things are going at this time. Most patients have pretty good habits at this stage, so you can think of this collection of thoughts as your own template for your future self. Someday you may struggle with your metabolism/weight. If that happens you should visit with your Bariatric Team because we can help, but also it can be very valuable to have a “reference point” of good habits laid out in your own language and your own life, a set of good habits that actually work for you.
Once you’ve got the foundation written down, update it with brief notes on a regular basis. This might be monthly, or quarterly. When you update and refer back to your 6-month habit foundation, you can spot trends and you have a better chance of finding problem behaviors at a point when they can be nipped in the bud. - Take pictures of yourself, on a regular basis. It’s really common to have difficulty adjusting one’s self-image as the weight comes down. The brain processes external images somehow differently than looking in the mirror, so get some pics of your new healthier self! Compare them against your starting point, and do this regularly. These pics are just for you, though you’re welcome to post them on Facebook if you like!
- Weigh weekly, not daily. Anytime beyond the first few weeks after surgery, random fluid shifts will be a bigger daily factor than changes in fat mass or muscle mass. Checking your weight every day and trying to make sense of it will drive you crazy. On the other hand, your weight is one easy indicator of your metabolic status so it is definitely useful to track on a regular basis.
So yes, the weight loss curve can be a bumpy ride at some points. Hopefully this will give you some information about the ride so you can take best advantage of each segment in your journey to better health!