What Is the Special K Diet?

Special K diet

Verywell / Debbie Burkhoff 

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At Verywell, we believe there is no one-size-fits-all approach to a healthy lifestyle. Successful eating plans need to be individualized and take the whole person into consideration. Prior to starting a new diet plan, consult with your healthcare provider or a registered dietitian, especially if you have an underlying health condition.

The premise of the Special K diet, sometimes also called the "K Diet," is simple. The diet is essentially a two-week challenge to consume Special K cereal as a meal replacement for two out of your three main meals each day with the promise of quick weight loss.

The Special K diet was developed as part of a marketing strategy by the cereal creator itself. In 2002, Kellogg’s funded a study with researchers from Purdue University to determine if consuming “ready-to-eat” cereal as a meal replacement twice a day would lead to weight loss. The study was published in the Journal of the American College of Nutrition with promising outcomes.

As a result, the Special K Challenge was marketed to the masses with a primary focus on women. The promise? Kellogg’s claims that the Special K Challenge is "a simple, great-tasting way to drop up to a jean size in just two weeks." According to the cereal maker, "the Challenge takes the guesswork out of weight loss by telling consumers to replace two meals with a Special K Cereal or Meal Replacement Bar followed by a reasonable, healthy third meal."

The Special K Challenge was a popular diet option for almost a decade, as it seemed like a viable way to lose weight quickly. For this reason, it appealed to many people. However, in 2013, Special K sales—along with the sales of many other "weight loss foods"—began to decline. Americans were losing interest in eating diet foods and began shifting their focus to choosing healthy food options. Since then, Kellogg’s has altered its marketing of the cereal.

However, the premise of the diet—along with all its limitations—still exists. Additionally, the Special K diet has evolved over time to include more branded products as meal and snack replacements.

Although it’s only followed for 14 days, eating the same cereal for two meals per day restricts you from consuming a variety of foods and benefiting from a variety of nutrients. Additionally, the diet doesn't establish eating patterns beyond the two-week period, so most people are likely to resort to their usual eating habits once the challenge is complete.

What Experts Say

"The Special K Diet encourages replacing meals with cereals and bars to promote weight loss—up to 6 pounds in two weeks. The health community warns that this is unsustainable. Plus, most Special K products are low in satiating fat and protein, so you may feel hungry."

Chrissy Carroll, RD, MPH

What Can You Eat?

The essence of the Special K Diet is that it’s a portion-controlled, two-week challenge that recommends substituting two meals per day with Special K cereal. In addition, the diet allows for portion-controlled snacks, vegetables, and fruits to support short-term weight loss or weight maintenance goals.   

The diet was never intended or marketed as a long-term weight loss solution, but instead, as a jumpstart option to help you meet an initial weight loss goal.

What You Need to Know

The Special K diet is simpler and has fewer rules than many other weight loss programs. Originally comprised of just Special K breakfast cereal and fruit, the diet has evolved since 2003 to include branded shakes, meal bars, cracker chips, and popcorn chips. Many Special K products are made from lightly toasted rice, wheat, and barley. Followers of the diet challenge can expect to eat:

  • 1 cup of Special K cereal with 1/2 to 2/3 a cup of skim milk for breakfast and lunch. A protein meal bar or protein shake can be substituted for lunch.
  • Fruits, vegetables, and other Special K food options, such as protein bars, granola bars, protein shakes, crackers, cracker chips, or popcorn, should be enjoyed as snacks.
  • No restrictions are placed on the third meal of the day.

There are no set times for meals or snacks.

Pros and Cons 

  • Special K products are cost-efficient

  • Not much planning required

  • Relatively safe and no associated health risks if followed for two weeks or less

  • May cause increased appetite

  • Limited options can be boring

  • Short-term plan

  • Doesn't create healthy habits

The Special K diet may seem like a simple way to lose weight, but the restrictive eating plan has its drawbacks.



While many diets require specific powders, supplements, and/or expensive ingredients, Special K products are reasonably priced. An 11.2-ounce box of Special K retails for less than $5.


The Special K diet takes the guesswork out of what to eat at meals. You simply swap out two meals per day with a portion-controlled bowl of cereal. You'll spend less time and money planning and preparing meals. Special K cereals and other products are familiar to most people and can be easily found at your local grocery store.


The Special K diet doesn’t require you to go vast periods of time without eating or to eat questionable supplements or products. It’s a relatively safe diet to follow for the short-term only.

Due to its limited choices and because Special K products are low in fiber and protein, the Special K diet is not considered a nutritionally balanced long-term eating solution.


Increased Appetite

There is a potential for increased appetite for those following the Special K diet. In the 2002 study, the two groups who consumed Kellogg’s cereal at two meals each day reported increased hunger versus the baseline groups.


Another drawback you may experience is boredom—eating the same foods over and over again each day can be mundane.


The Special K diet is also not a long-term solution—it's marketed as a short term solution to follow for two weeks only. It also provides limited nutrients. Eating the same foods over and over can limit the overall amount and variety of nutrients you consume.

Doesn't Create Healthy Habits

By following a short-term diet or challenge with specific meal replacement products, you’re not establishing good-for-you habits or learning how to incorporate healthy, real foods into your diet for the long-term.

Is the Special K Diet a Healthy Choice for You?

The Special K diet is similar to other meal replacement diets such as SlimFast or Nutrisystem in which at least one, if not all meals throughout the day, are replaced with a specific, branded food product. What the diets offer, however, doesn't meet all optimal nutrition recommendations.

The United States Department of Agriculture (USDA) shares guidance for improving and maintaining overall health and well-being. These dietary recommendations include calorie guidance and tips for a healthy, balanced diet. The Special K diet meets some of the criteria, but not all.

The Special K Diet, like the other meal replacement diets, places some control on the foods you eat and manages overall portions. These meal replacement diets primarily work by limiting the overall daily calorie intake.

For instance, in the 2002 study, Purdue University researchers found that the two different groups eating cereal for two meals per day reduced their overall calorie intake by an average of at least 600 calories per day.

Taking in fewer calories than you use each day can help you achieve your weight loss goals, but you should achieve this reduction in a healthy and balanced way. Use this calorie calculator to determine your daily intake to meet your weight loss goals.

While the other meal replacement diets provide a variety of healthy foods and focus more on controlled portions, the Special K Diet relies primarily on Special K cereals, which limits the variety of food and nutrients recommended by the USDA. This is likely why the diet is only recommended for two weeks.

Health Benefits

While proponents of the Special K diet claim that it's a quick, cost-effective way to lose weight, the restrictive nature of this eating plan is not supported by health and nutrition experts. On the plus side, however, the diet is low in saturated fat, cholesterol, and sodium.

Special K cereal is a good source of vitamins A and D and an excellent source of vitamin C, iron, thiamin, riboflavin, niacin, folic acid, and vitamins B12 and B6, and can be consumed as part of a healthy, well-balanced diet.

Health Risks

Though there are no common risks associated with a short-term Special K diet, this eating plan restricts food groups that provide important nutrients. Special K cereals are not typically made with whole grains. Therefore, they’re low in fiber (foods higher in fiber can help you feel more full after eating them). For example, 1 cup of Special K Red Berries cereal has just 2.6 grams of fiber or about 10% of the daily value. The cereal is also low in satiating protein, providing just 2 grams per 1-cup serving.

The result of Special K's nutritional profile was evident in previous studies which reported increased appetite while consuming the ready-to-eat cereal for two meals per day. The cereal is also low in potassium but the diet recommends eating fruits and vegetables with the meals and as snacks, which are high in potassium.

A Word From Verywell 

While the Special K diet promises losing up to six pounds in just two weeks, the diet was only popular for about 10 years before sales of the products began to decline. The diet itself is not necessarily dangerous, but it doesn’t promote healthy or sustainable eating habits and is not viewed as a long-term weight loss solution by nutrition experts.

Following a regimented or highly restrictive diet with the goal of losing weight is often not the path to healthy, long-term weight loss or the answer to all of your health goals. Many factors like exercise, sleep, meditation, and more play a major role in your overall health. Aim to eat a balanced healthy diet that fits your lifestyle.

Remember, following a long-term or short-term diet may not be necessary for you and many diets out there simply don’t work, especially long-term. While we do not endorse fad diet trends or unsustainable weight loss methods, we present the facts so you can make an informed decision that works best for your nutritional needs, genetic blueprint, budget, and goals.

If your goal is weight loss, remember that losing weight isn’t necessarily the same as being your healthiest self, and there are many other ways to pursue health. Exercise, sleep, and other lifestyle factors also play a major role in your overall health. The best diet is always the one that is balanced and fits your lifestyle.

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6 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Kellogg's. Jeans don't lie. Updated September 2007.

  3. U.S. Department of Agriculture. Dietary Guidelines for Americans. Updated December 19, 2018.

  4. Gianturco P, Perez V. A meta-analysis of intervention trials examining the effects of a simple 2-week weight loss program on body weight and waist circumference. J Nutrition Health Food Sci. 2016;4(1):1-9. doi:10.15226/jnhfs.2016.00154

  5. Special K Red Berries Cereal. FoodData Central. U.S. Department of Agriculture. Published April 1, 2019.

  6. Rebello CJ, Johnson WD, Martin CK, et al. Instant oatmeal increases satiety and reduces energy intake compared to a ready-to-eat oat-based breakfast cereal: A randomized crossover trial. J Am Coll Nutr. 2016;35(1):41-9. doi:10.1080/07315724.2015.1032442

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