Special K Vs. Slim Fast

Both Kellog's Special K cereal and Slim Fast diet shakes are marketed as effective weight loss products because of their low calorie content. While low-calorie products can assist you on a diet, other factors, such as nutrient content and ability to keep you feeling full are important as well. You should consult a doctor before beginning any weight loss plan or substantially altering your dietary intake.

Calorie Content

According to the official website for Slim Fast, one Slim Fast diet shake contains 190 calories. This is 70 calories more than 1 cup of Special K cereal, which contains 120 calories, according to Kellog's. One cup of Special K with 1/2 cup of skim milk contains 160 calories. Although consuming fewer calories than you expend is critical for weight loss, 30 calories is unlikely to make a difference--the Mayo Clinic's calorie expenditure information notes that about 10 minutes of walking could burn off 30 calories.

Protein Content

According to research from the March 2009 issue of the "International Journal of Obesity," protein intake may have a significant effect on weight loss. A study from the journal found that those who consumed diets higher in protein lost more fat and maintained weight loss after dieting than those consuming lower-protein diets. Because of this, you may want to choose a high-protein product for weight management. Slim Fast's official website notes that each shake contains 10 g of protein, while one serving of Special K provides 6 g of protein, according to Kellog's.

Sugar Content

Another important nutrient to consider in weight management and general health is sugar. The Harvard Medical School explains that sugar, particularly sugar in drinks, appears to be related to obesity. According to the nutrition information from Kellog's, 1 cup of Special K cereal contains 4 g of sugar. This is significantly less than the amount contained in Slim Fast shakes-18 g per shake, according to Slim Fast's website.


As the Mayo Clinic explains, dietary fiber is a vital nutrient that has many benefits, from potential reduction of blood pressure to aiding in weight management. The Mayo Clinic explains that fiber helps you feel fuller for a long amount of time. According to Slim Fast, each shake contains 5 g of fiber, which is 20 percent of the daily recommended intake. Kellog's Special K contains less than 1 g of fiber per cup.


Because Slim Fast shakes come in separate containers, they can be convenient for work or school. However, Slim Fast shakes are not resealable and contain milk, so they should be refrigerated. Meanwhile, Special K cereal does not need to be refrigerated, but it is sold in large boxes, so you will have to package it yourself for portability.

Vitamin and Mineral Content

Both Special K and Slim Fast contain a number of different vitamins and minerals. Slim Fast shakes contain more nutrients overall, with 23 vitamins and minerals, compared to the 15 found in Special K.