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The Truth Behind Sudden Weight Gain On Keto

I started a ketogenic diet over 15 years ago to lose weight, which is why most people start a ketogenic diet. However, specific individuals may experience sudden weight gain when starting keto for a variety of reasons.

Sudden weight gain on a keto diet is typically a result of a few reasons. Some of the reasons you may experience sudden weight gain include eating more than you think, the body undergoing too much stress and retaining water, gaining muscle, or “cheat days” taken too far. 

I'll go over in detail why you may be gaining weight, and EXACTLY what you should do to steer your weight loss in the correct direction.


Sudden Weight Gain On Keto

Often enough, people are misled to believe that eliminating carbohydrates from the diet is enough to lose fat. Eventually, many people end up questioning why they might not be losing weight while in ketosis. 

And the answer is quite simple; you don't have to be in ketosis to lose weight. 

Think about it, how many people do you know, possibly even yourself once upon a time, who has lost weight while NOT following a ketogenic diet? 

The answer… plenty of people!

I'm In Ketosis But Not Losing Weight, Here's Why (5 Reasons)

You're overeating.

 Calories still matter! 

While you may have been led to believe that calories don't matter, I can assure you that they do. Regardless of which diet you choose,  fat loss will ultimately come down to expending more energy (calories) than you're taking in. 

Research shows that when allowed to eat ad libitum1, subjects following a ketogenic diet tend to eat less on average. The study doesn't say that it's impossible to overeat on keto, but by nature, many individuals find it easier to stick to a caloric deficit following a ketogenic diet.23 

And as you may know, dieting is hard, especially when you're starving 24/7. The satiety you experience is part of what makes a ketogenic diet a great way to drop the pounds without feeling like your continually starving yourself.

It's not 100% necessary to track calories. However, I always recommend my clients track calories for a couple of weeks to get a general grasp of what portion sizes of foods they enjoy look like. Eventually, they can transition into a more intuitive approach.

Counting calories and tracking macros can become a skillset you can rely on when you do not see the progress you're after, or your goals become even more serious. 

 Extreme results require extreme measures. 

The solution

You may get a starting point of how many calories and what your macros should be by heading to the keto macro calculator. The calculator will help give you a starting point based on your stats, goals, and preferences. 

It's imperative to use a scale to measure your portion sizes. You'd be surprised how much something like one serving of peanut butter looks like. Eating a little more than you think consistently could easily cause you to gain weight on keto.

For tracking calories and macros, I would suggest using an app such as MyFitnessPal or Carb Manager to log your foods and track progress. It's the art of monitoring progress and knowing when to make adjustments that make the difference between success and stalled progress.

You’re retaining water

Water retention on keto

The scale can only measure the force that exists between you and the earth (i.e., gravity). The scale can't measure whether or not you're losing fat, gaining muscle, or holding onto a bunch of water weight.

Water retention is a common occurrence in many people trying to lose weight. The act of losing weight itself is a stress on the body. Combine the stress of losing weight with the stress of everyday life, and there's a good chance you may be retaining water. 

When you're under too much stress, mental and/or physical, cortisol, and antidiuretic hormone (ADH) rises. ADH and cortisol, the stress hormone, directly influence fluid retention and water weight. Antidiuretic hormone is a chemical produced in the brain that signals the kidneys to expel less water. 

Additionally, hidden carbs may be another underlying reason you may notice a sudden gain in weight on keto due to water retention. If you've introduced new foods into your diet, make sure you're checking the nutrition label or asking if there are any added ingredients you may not be aware of.4

You may also be retaining water if you've just begun a new exercise program. 

The solution

Diet breaks can mitigate the stress of dieting.

You heard that correctly.

Taking a break from trying to lose weight will not only reduce your stress from dieting constantly, but you may even see more significant long term progress. By taking periodic breaks and bringing up your calories to maintenance 5, you may reduce the side effects that come along with weight loss.6 

Think of diet breaks as a three steps forward one step back approach to long-term sustainable weight loss, except the one step back isn't a step back. You should be maintaining weight during these periods of diet breaks. Achieve maintenance by bringing up your calories up to a level of calories that has you neither gaining or losing weight. 

There hasn't been a study on what the most optimal diet break length is, but current research has used 2 weeks on 2 weeks off approach in addition to 3 weeks on 1 week off schedule with great success. Diet breaks may increase the length of time it takes to reach your goal, but many find this approach more sustainable and more comfortable to maintain weight loss. 

Besides, will it matter ten years from now whether or not you took 12 weeks or 12 months? Not really. You'll only remember the fact that you got to the finish line, and developed new habits and a lifestyle that allowed you to maintain your progress.

In addition to the physical stress from dieting, stress is also psychological. While certain things may not be under our control, managing your different stressors outside of dieting can help with water retention.

Finding hobbies and activities you enjoy can help relax and mitigate stress. Meditation programs have also been shown to produce small to moderate reductions in psychological stress. 

Some great ways to get started with meditation that I've found are the Headspace and Simple Habit App for both iOS and Android devices. 

You're gaining muscle.

A common reason people starting keto notice a sudden increase in weight is they're gaining muscle. Alongside a new diet, many people decide to adopt a healthier lifestyle that includes lifting weights or resistance training (boot camps, CrossFit, etc.). 

While the scale MAY be increasing, this is not necessarily a bad thing. Gaining quality muscle will not only set you up for better health and longevity, but it will bring you closer to achieving the desired look you're after. 

Many people who begin working out for the first time are also more susceptible to “newbie gains.” When first adopting a resistance training program, it's much easier to put on muscle than someone who's been training more than a couple of years. You even have an increased chance of body recomposition, gaining muscle WHILE losing fat. 

If you're interested in learning how to take advantage of this new stimulus (resistance training) and reap the benefits of putting on muscle while potentially losing fat, take a read at my article on how to bulk on keto

Muscle is also more metabolically active than fat. Gaining muscle increases your resting metabolic rate (RMR), the number of calories you burn at rest. The more muscle you have, the more calories you burn, the more you can eat while still losing fat. 


To go along with the earlier reason, water retention, people who begin working out for the first time often gain a pound or two from increased water storage in the muscle. This weight gain is temporary and should not be confused with actual weight or fat gain. 

The solution

Since a scale can't measure what kind of weight your gaining, a better way to track progress is to use one or a variety of other measurements. Easy and inexpensive ways to track progress include taking progress photos or using a simple tape measure. 

If you notice a sudden increase in weight, but your waist measurements are decreasing, there's a good chance you're gaining muscle. Taking measurements and progress photos every other week or once a month is, in my opinion, a better way to track your weight loss progress. 

Cheat days gone too far.


It often comes up with almost every diet, the infamous cheat day. Have foods in moderation once in a while, even on keto, but a day of bad eating can set you back. 

First, if you cheated by eating foods with plenty of carbohydrates, you can expect to retain some extra fluids. Every gram of carbohydrate that your body stores, an additional 3 grams of water are also stored.

 A meal or day filled with an additional 100 – 200 grams of carbohydrates can easily add a pound or two of additional water weight, in addition to the extra food volume sitting in your stomach.  

While this weight gain is only temporary, it may take a few days for the water to subside. If you have cheat days or meals weekly, you may never notice the water weight dissipate as you reintroduce carbohydrates as it's about to happen.

Also, water weight aside, it's possible to undo an entire week's progress with a day of bad eating, as illustrated below. 


The solution

Depending on what works best for you, I would recommend one of the following:

  • Skipping the cheat day and having a free meal instead
  • Reserving cheat days or meals only for special occasions
  • Staying keto by filling your craving with a keto-friendly version

By limiting your “cheat day” to a meal, you minimize the damage that you can potentially have on your diet. I would also reserve the free meal for dinner since it's typically the meal we're most social at and limits the possibility of it turning into an entire day. 

Instead of built-in weekly cheat days or meals, try to stick with your diet and reserve them for special occasions. For instance, maybe you have a weekly cheat day on Saturdays, but something unexpected comes up like a business lunch or an out of town guest, what do you do?

Saving your “free meals” for these occasions gives you the flexibility of getting more use out of them than an arbitrary day devoted to gluttony. 

Lastly, a great way to offset some of that bloat that comes with a carb-filled cheat day or meal is by keeping it keto-friendly. There's plenty of recipes floating around that you can whip up at home that won't leave you feeling disgusted and bloated the next day. 

You're inflamed


Inflammation can stem from anything in your diet that your body doesn't agree with. Interesting enough, certain keto-friendly foods can affect inflammation in your body leading to water retention, a slowed metabolism, and possibly weight gain.

Inflammation isn't necessarily always a bad thing. Inflammation can work to help protect your body from viral and bacterial illnesses. 

On the other hand, chronic inflammation is linked to an increased risk of a plethora of diseases such as diabetes and obesity.78

Here are some keto-friendly foods you may be including in your diet that may be causing more harm than good. Remember, just because you can eat something on keto doesn't necessarily mean you should. 

Trans fats

Trans fats are considered by many to be the worst type of fat you can eat. However, not all trans fats are bad. Trans fats occur naturally in certain foods such as dairy and meat. It's the artificial trans fats that you should avoid at all costs.

Artificial trans fats have been shown to cause inflammation and increase disease risk in addition to lowering HDL (good) cholesterol.910

Consuming artificial trans fats is also linked to increased C-reactive protein (CRP). CRP is a protein made by your liver that sent into your bloodstream in response to inflammation. 

High levels of CRP may indicate that there's an infection or a chronic inflammatory disease, in addition to an increased risk of heart disease. In one study, CRP levels were 78% higher among women, with the highest reported trans fat intake.11

A CRP test is also used to help determine the risk of a second heart attack. Those who've suffered from a previous heart attack are more likely to have another event if they have high levels of C-reactive protein in their blood.

Common ‘keto-friendly' foods that may contain artificial trans-fats include foods with vegetable shortenings, margarine, coffee creamers, fried fast food, and any food that lists partially hydrogenated vegetable oil on the label.

Vegetable and seed oils

It's not that vegetable and seed oils are inherently bad, but the current omega-6 to omega-3 ratio is between 10:1 and 20:1.2. A disproportionate level of omega-6 to omega-3 is thought to be associated with many chronic and inflammatory diseases such as obesity.12

You can balance your omega-3 to omega-6 ratio by eating more omega-3-rich foods, such as fatty fish, pasture-raised eggs, and grass-fed meats to reap the anti-inflammatory benefits of omega-3's. 

What the exact ratio of omega-6 to omega-3 should be is still up for debate, but a ratio of 4 to 1 was associated with a 70% decrease in total mortality.13 Strive for a ratio of 4:1 and as close to 1:1 as possible. 1:1 can be quite difficult without being very strict with your food choices but maybe the most optimal. 

Processed meat


Processed meats are quite popular amongst many ketogenic dieters. Common types of processed meats found on a ketogenic diet include bacon, turkey bacon, smoked meat, and sausages.

These also include food products such as spam and vienna sausages, which are keto friendly.

While you don't need to eliminate all processed meats, they also shouldn't make up the majority of your diet. Processed meats contain more advanced glycation end products than other meats.

Dietary advanced glycation end products are known to contribute to increased inflammation, which leads to diseases such as diabetes, cardiovascular disease, and obesity.14

When it comes to meat consumption, limit processed meats, and eat the bulk of your protein from whole-fresh meat sources. 

What's The Average Weight Loss During Ketosis

Now that we've gone over why you may be experiencing sudden weight gain on your keto journey, another common trap is having too high expectations when it comes to weight loss.

It may not be that you're gaining weight, but you do not see the weight come off fast as you would like, so what's the average weight loss you should expect following a ketogenic diet?

Keto weight loss during the first week

During the first week of a ketogenic diet, you may expect to lose anywhere from 1 to 5+ pounds. Bear in mind, much of the weight lost during the first week on a ketogenic diet is due to decreased carbohydrates and rapid water loss.

After the first couple of weeks on keto, the average weight loss will usually depend on how much weight you have to lose. The more fat you have to lose, the more weight per week you can expect to lose.

After the first two or three weeks on keto when the body has begun to renormalize its fluid levels, you should expect to lose anywhere from 0.5 – 1.5% of your body weight per week. The more fat you have to lose, the more towards, the higher 1.5% you can expect to be. 

 Extremely overweight individuals may get away with even higher rates of fat loss without risking much if any, muscle loss. 

Of course, this will also come down to your diet and how much you're eating. As discussed early on, if you're not eating in a caloric deficit, you won't lose weight no matter what you do.

Instead, the more fat you have to lose, the faster you can and expect to lose weight. The less fat you have to lose, a slower rate is expected merely due to having less to lose and an increased chance of losing muscle mass.

Losing weight too quickly may lead to an increased chance of muscle loss and weight re-gain if you don't develop new habits and lifestyle choices. Losing weight rapidly when you don't have as much to lose also becomes much harder as you have to either eat very little or increase activity to high amounts.

What's great at using a percentage of body weight versus an exact number every week is the rate of weight loss will scale according to how much fat you have to lose.

How To Gain Weight On Keto

As you have read, experiencing a sudden weight gain on keto isn't always necessarily a bad thing. If you're new to working out, there's a high chance that you're putting on muscle and retaining some extra fluid. 

Being new to resistance training is the prime opportunity to change your appearance drastically as you can potentially gain muscle and lose fat at the same time. If this applies to you, I would highly recommend you give my articles how to bulk on keto and the ultimate keto bodybuilding guide a read.

The Bottom line

Sudden weight gain on keto may stem from increased water retention to even gaining muscle. Unless you're overeating, there's a good chance that the increase in weight is temporary and should be nothing to worry about. 

If you still find yourself not losing weight on keto after monitoring calorie intake and managing stress, it may be time to take a break from dieting. A diet break can do a lot to reduce stress and adaptations to dieting while providing a psychological break. 

Lastly, be realistic when it comes to losing weight. There's a good chance you didn't put all that weight on in a month, so don't expect to lose it in one. Aim for a weight loss of 0.5 – 1.5% of your body weight per week. Dieting at a more sustainable rate will help preserve muscle and improve adherence. 

Remember, it's not a race to see how fast you can lose weight. You must lose weight and maintain weight loss by forming better habits and lifestyle choices developed over time.

Frequently Asked Questions

Why am I putting on weight on a low carb diet?

There might be a few reasons behind why you're putting weight on a low carb diet. It may be that you haven't reduced the carb content enough. Alternatively, you could be consuming too many fats!

What is the whoosh effect on keto?

The whoosh effect refers to the period of noticeable weight loss when you're on a low carb diet.


Founder of The Art Of Keto.

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