The Special K Diet Plan Review
Cereal Diet Plans and Weight Loss

The Special K Diet Plan (Special K Challenge) has evolved but will it still help you to lose weight in a healthy way? WLR investigates . . .

The Special K Diet Plan Review

By wlr Nutritionist Sara Kirkham

Although the Kellogg’s Special K challenge - "Drop a jeans size in 2 weeks" - isn’t marketed by Kellogg’s any longer, people still like the diet because it’s such a simple idea.

The promise of losing up to 6 pounds in two weeks by “… eating a bowl of cereal for breakfast and lunch, then a regular meal for dinner” sounds very easy. But although simplicity in an eating plan is a good thing, is this diet really that good?

Does the diet work?

This diet can easily create a calorie deficit. A small bowl of cereal provides fewer calories than many breakfasts and certainly less calories than a typical lunch. Kellogg’s also suggested swapping any snacks to a Kellogg’s cereal bar or a piece of fruit.

As with all weight loss diets, if you create a calorie deficit, you will lose weight.

However, losing weight is one thing, but maintaining that weight loss over a prolonged period of time requires an eating plan that isn’t too restrictive. This way, you can remain on the eating plan, and it should also deliver all the nutrients required for continued good health.

This is where the Special K diet crumbles into dust at the bottom of the box .

It can provide a short-term weight loss over a couple of weeks (which is actually the time period Kellogg’s suggest it is followed for), but is not sustainable (for psychological and health reasons) over a longer period of time.

What are the pros of a cereal diet like this?

Simplicity and convenience

It’s not difficult to follow or plan – you simply have to remember to buy a box or two of breakfast cereal, and have it with you at breakfast and lunchtime.

Unlike many other diet plans that may exclude several food groups, require food combining or drinking odd concoctions, this is probably one of the simplest diet plans around.

Cereal bars are even more convenient with the added ease of being able to carry them around and consume them in most work settings.

It may even help some people eat more regularly – if you are prone to missing breakfast or lunch due to lack of time, this diet does provide very quick and easy meals options.

Should create a calorie deficit

As well as being easy to follow, this diet could be quite low in calories, depending upon the evening meal consumed.

It’s quite possible – and not unusual – for us to make up for a lower calorie intake through the day at the evening meal.

Some research on intermittent fasting has reported favourable results for weight loss, and shown that many people do not actually overeat at the next meal or on non-fasting days.

At the same time, there is also research which shows that low calorie consumption can cause us to more than make up for that energy deficit at the next meal in a number of ways:

  • We tend to choose higher sugar foods
  • We choose foods higher in fat
  • We consume larger portions and consume a larger number of calories.

With more time to relax and eat a larger meal in the evening, the reduced calorie intake you have achieved through the day can easily be lost with an over-large evening meal.

However, with a palm-sized portion of protein, a small serving of a starchy carbohydrate and veggies to make up the rest of the meal, the Special K diet can hit the spot as far as calorie reduction goes.

If you consider how many calories your normal breakfast and lunch might contain, and compare it with the average caloric content of a small bowl of Special K with skimmed milk, you are clearly creating a calorie deficit... and when you create a calorie deficit, you lose weight.

Breakfast comparison Calorie content
Two slices of toast with butter and jam 318.0
Small bowl (35g) of Special K with 100ml skimmed milk 147.9
Calorie saving - breakfast swap 170.1 calories
Lunch comparison Calorie content
Tesco ham and cheese sandwich 443.8
Small bowl (35g) of Special K with 100ml skimmed milk 147.9
Calorie saving - lunch swap 295.9 calories
Snack comparison Calorie
McVitie's digestive biscuits (2) 141
Kellogg's Red Berry cereal bar 90
Calorie saving -snack swap 51
Total calorie saving for these swaps 517 calories

*Information from the wlr food database.

So if you are creating a calorie deficit of 500 fewer calories each day, you could lose around a pound a week.

And the cons?

Lack of diversity and nutrients

Eating the same foods every day, and especially the same thing twice in one day, will limit the range of nutrients in your diet.

We require a wide variety of nutrients for health, and whilst cereal will provide carbohydrates and B vitamins, it doesn’t provide all the nutrients needed for good health, such as calcium.

Swapping your usual meals for cereal reduces the opportunity to consume 5 a day. Doing this particularly limits vegetable intake.

It's easier to add a few berries to your cereal than a green salad or some carrots. This reduces your range of anti-oxidant and anti-inflammatory plant nutrient intake.

At 0.8g per 30g serving, Special K is not a high fibre cereal - porridge oats or Weetabix contain much more fibre, so would be a healthier option.

However, with 113.7 calories per serving compared to 136 (2 Weetabix) and 142 (serving of porridge oats), you can see why Special K was chosen by Kellogg’s for the weight loss plan.

Cereal Comparison Chart
Cereal Sugar Content
per 100g
Fibre Content
per 100g
Special K 17g 2.5g
Weetabix 4.4g 10g
Scott's Original Porage Oats 1g 9g
Special K vs Weetabix and Porridge - Fibre and Sugar
Special K vs Weetabix and Scott's Porage Oats - Fibre and Sugar in grams per recommended serving sizes.


Special K and most other breakfast cereals tend to be low in fibre, fat and protein – three things that promote the feeling of fullness (satiety).

Carbohydrates are the easiest type of macronutrient to digest. So the quicker digestion plus low fat, fibre and protein content of this meal may mean that you feel hungrier more quickly than usual, and may snack more between meals.

High in sugar and refined carbohydrates

Many breakfast cereals contain added sugar.

Special K contains 17g of sugar per 100g. This is classed as a moderate sugar product.

Which doesn't sound too bad until you compare it to the other cereals in the example above.

A high sugar content gives cereals such as Special K quite a high glycaemic index (GI) of 69. The GI of a food relates to the amount of glucose (a simple sugar) in a food, and the time it takes for that sugar to be absorbed into the blood stream.

  • High GI foods have a fast absorption time and will elevate blood glucose levels quite quickly
  • Low GI foods are digested and absorbed more slowly, and with a slower release of glucose into the bloodstream, these foods incite a lower insulin release and more sustained energy levels

The problem with having a high GI is that a food elevates blood glucose levels quite quickly, and we secrete the hormone insulin in response in order to bring our blood glucose levels back to normal.

Insulin is an anabolic hormone, which means it promotes the laydown of various body tissues, including body fat. When insulin is released in response to an elevated blood glucose level, it reduces the glucose in the blood stream in a number of ways:

  • It stimulates body cells to take in glucose, so lowering glucose in the blood
  • It stimulates cells to use glucose for energy – even favouring glucose over fat for fuel. This isn’t great if you are trying to use up excess fat!
Relationship between sugar levels, insulin and hunger

Effects upon health

There is an increasing body of evidence linking elevated cholesterol levels and impaired cholesterol metabolism to a diet rich in refined carbohydrates with a high GI.

Ravid et al illustrated that a high glucose concentration after a meal increases intestinal cholesterol absorption.

A diet high in sugars and refined carbohydrates also contributes to conditions such as insulin resistance, metabolic syndrome and diabetes.

These conditions are all linked with increased levels of oxidative stress. Oxidative stress is linked with higher levels of oxidized cholesterol, and therefore linked with increased risk of cardiovascular disease.

Low protein content

Protein takes a longer time to digest than carbohydrates, and in doing so, increases our satiety (feeling of fullness) and helps to prevent us from snacking.

It is this feature that is thought to contribute to the successful weight loss often seen in higher protein diets (Leaf and Antonio), and many food manufacturers are trying to promote the protein content of their products, or add additional protein to them.

Kellogg’s now offer some higher protein products, although these do not really provide a lot of protein.

Their ‘Protein, blackcurrant and pumpkin seed bars’ are 14% protein, but with each bar weighing 28g this provides only 3.92g of protein, and these still contain a moderate amount of added sugar.

Weetabix Protein provides 7.6g of protein per 40g serving, but as with most ‘high protein’ cereal products, the additional protein added is often wheat gluten, which can cause digestive upsets for some.

Unrefined whole grains are better for weight control

Researchers have found that processed foods require less energy to be digested and absorbed than whole foods.

In one study (Barr and Wright) it was found that a processed food meal of the same calorie density as a whole food meal decreased postprandial energy expenditure (the amount of energy used up in digestion/absorption) by nearly 50% compared with the wholefood meal. So an iso-calorific portion of a less refined, wholegrain cereal would provide a lower net calorie gain than a processed cereal such as Special K.

Lack of additional support for weight loss

There are no recommendations on the content or portion size of the evening meal, and if you have become over-hungry from consuming just two bowls of cereal, and overeat, you could easily undo any earlier calorie deficit.

There is also no mention of regular exercise in the Special K cereal diet to help weight loss.

How can I make this type of diet work for me?

There is no doubt that replacing many typical meals with a small bowl of cereal will create a calorie deficit and could enable weight loss. To use this to your advantage whilst avoiding the pitfalls of this diet, try the following tips:

  • Limit the serving size of cereal to a small bowl (35g) so you aren’t eating a large portion of refined breakfast cereal.
  • Add a handful of fruit to the breakfast serving (any fruit except for banana, which is more calorific than most fruits, although it does have some healthy nutritious benefits too) – adding fruit will increase fibre and micronutrient intake.
  • Reduce the cereal serving a little and add a dessertspoon of nuts or seeds and/or a spoonful of unsweetened 0% fat yoghurt or protein powder to the lunchtime serving - meals higher in protein will keep you feeling fuller for longer, and have a metabolic advantage over carbohydrate foods.
  • Adding fruit or yoghurt/nuts/seeds will also increase the volume of food consumed – whilst this may increase calorie intake, it could help to avoid snacking in between meals, which is more likely to be counterproductive.
  • Try swapping your evening meal for a bowl of cereal instead of breakfast/lunch on some days – this will create an even larger calorie deficit than swapping with typical breakfasts or lunches. This might be feasible on days that you are working (and therefore eating) later, or on days when you need a light tea because you are going out or exercising. Having a protein-rich breakfast or lunch instead will help to power you through the day too.
  • Try the cereal swaps on working days, or Monday – Friday, and choose lower calorie breakfasts and lunches than your usual choices on other days to make the diet more diverse and increase your nutrient intake. This will also provide alternatives to eating cereals for a healthier long term eating plan that will enable weight loss and then maintenance.
  • Try replacing normal meals with a bowl of cereal such as Weetabix or porridge oats, which are higher in fibre than Special K – this is still likely to create a calorie deficit compared to what you might normally eat, but the higher fibre content will help to keep you fuller for longer.
  • After two weeks, swap the cereal meals for vegetable and protein-based meals such as the ones suggested below. At the same time, if you limit/avoid snacking, keep alcohol to a minimum and reduce the size of your evening meal, you will create calorie deficits in other areas of your diet to enable you to continue to lose weight.

What weight loss results can I expect?

The Special K diet suggests you could lose up to 6lbs over 2 weeks. But you'd need to create a calorie deficit of approximately 1500 daily - very hard for most people and impossible for some.

Calorie deficit = number of calories needed to maintain weight - number of calories eaten (assuming number of calories eaten is lower than number of calories needed to maintain weight).

For Example:

If the number of calories required to maintain your weight is 2000, and you eat only 1500, you have created a calorie deficit of 500.

The amount of weight you can lose will depend on the calorie deficit you can create.  A deficit of 500 - 1000 calories a day should produce a weight loss of 1-2lbs per week.

Alternatives to a full cereal diet

A day’s menu using alternative cereals could look like this:

Breakfast: 2 Weetabix Protein with skimmed/almond/soya milk and a handful of blueberries.

Lunch: 35g porridge oats with 75ml skimmed or almond/soya milk. Add a teaspoon of flaked almonds, a teaspoon of pumpkin seeds and a dessertspoon of either Total 0% fat yoghurt or CoYo plain coconut yoghurt and a sprinkle of cinnamon.

Dinner: 2 egg omelette with added mushrooms, tomatoes and rocket and 10g of parmesan cheese, served with a large green salad. The eggs can be replaced with tofu in a stir fry for a vegan option, also using non-dairy cheese.

Other healthy breakfast ideas:

Unsweetened 0% fat yoghurt (Total) or plain CoYo coconut yoghurt – 2 large tablespoons, with added fruit if you wish (1/2 cupful) and a dessertspoon of mixed seeds or nuts.

Banana and egg pancake: 1 banana and 2 eggs make enough for 2 people. Blend together and pour into a frying pan, making small pancakes. Turn over when slightly browned.

Poached egg (1) on a bed of spinach or with asparagus spears (raw or grilled).

Scrambled egg (2) with rocket or spinach mixed into it. Grilled tomato/grilled mushroom is optional.

Healthy lunches:

Home-made or carton fresh vegetable soup

One small tin of tuna fish or a small breast of grilled chicken with salad vegetables, no dressings.

Mediterranean salad – half a reduced fat mozzarella ball, half an avocado, 2 vine tomatoes, a handful of rocket, 3 chopped olives, cucumber, 5 spears of griddled asparagus, fresh basil.

Healthy dinners:

Frittata (2 eggs) with rocket, tomatoes, red onion, mushrooms, peppers, peas and asparagus.

Grilled salmon steak or reduced fat halloumi with broccoli and baked sweet potato.

Stir fry: red onion, garlic, mushroom, kale, peppers, peas, sweet corn – meat, fish or mixed seeds/pine.

Steamed fish or grilled tofu with a cupful of dry roasted squash, and asparagus or mange tout.

Spaghetti (made from courgette/carrot/pumpkin/squash) with pan-fried (use 1 cal oil spray or limited oil) red onion, mushroom, tomato, garlic and peppers.

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Further Information

For more information visit the Kelloggs Cereal Diet website

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