Morgan is a doctoral candidate in the field of clinical nutrition and nutritional neuroscience, having received her bachelors degree from Central Washington University.
The Slim Fast Diet is oriented around what Slimfast calls the “3-2-1” plan, a nod to the diet’s structure of two Slim Fast brand meal replacements, three 100 calorie snacks options, and one 500 calorie meal that is chosen (and prepared) by you. Meal replacements are available in two forms: the ubiquitous Slimfast ready-made “shake” (available in eight flavors), powdered protein beverages that you mix yourself by adding the powder to nonfat milk), and six flavors of “meal replacement bars”. The plan also offers “snack bars”, which differ from the meal replacement bars, and are meant to be consumed as one of the three, 100 Calorie snacks allotted to dieters. Instead of the Slim Fast line of snack bars, dieters can choose to consume 100 Calories worth of carrot sticks, nonfat yogurt, pistachios, sorbet, or pretzels, or an orange, banana, pear, or 100 Calories worth of grapes or cherries. For the self-chosen 500 Calorie meal (the only meal of the day that is self-regulated and not left up to the list of “permissible snacks/meals” via Slim Fast), dieters are permitted to select whatever they’d like, as long as it does not exceed 500 Calories. Slim Fast does advise that dieters fill half their plates with vegetables, ¼ with lean protein, and ¼ with starch, but the components are left to the choice of the individual.
The Slim Fast diet dates back to 1977, and has since marketed itself as a quick and simple weight loss solution, via the use of “meal replacements.”
As the Slim Fast Diet eliminates the majority of non-Slim Fast food consumption, it’s a very difficult plan for many dieters to stick with long term. Typically, any weight lost during the diet will be regained once the dieter begins to forgo their “Slim Fast” meal consumption, because the Calorie regulation system (provided by the Slim Fast meal structure) will be gone as well. While starting with the Slim Fast diet, losing weight, and then incorporating real food into your diet while accounting for Calories would allow for long-term maintenance, the Slim-Fast diet does nothing to teach users to make that change healthfully. Nothing short of nutrition education and behavioral change models (provided by all effective diets) can help a dieter successfully maintain a lower weight long-term.
The Slim Fast diet does require that you purchase their products for daily consumption, although the exact cost will vary dependent upon your region and grocery store. A package of eight prepared shakes (eight meals’ worth), typically costs around $10, five meal replacement bars (five meals’ worth) cost around $5, and a 12 oz container of beverage powder (12 meals’ worth) costs around $9. A package of six Slim Fast snack bars (six snacks’ worth) costs around $4.
The Slim Fast Diet, thanks to its reliance on meal replacements, requires very little time. However, the time saved on meal prep ultimately means ineffective behavioral change and poor nutrition.
The Slim Fast diets fails to provide quality nutrition through whole foods, and may leave dieters at risk for nutrient deficiencies.
The Slim Fast diet typically ranks very low in the general opinion of Dietitians and Doctors. The Slim Fast diet teaches little to no self-regulation, and provides little by way of positive behavioral change. The Slim Fast diet ultimately fails to teach dieters how to behave in a way that is physically and psychologically healthy, and does not equip dieters with ways to manage food in the “real world”, or outside of the 3-2-1 plan. Furthermore, the 3-2-1 plan fails to deliver optimal nutrition, and will likely leave dieters hungry for more, physically and psychologically.
Benefits: The Slim-Fast diet is very portable, and requires little to no food prep time.
Downsides: This diet can fail to meet appropriate nutritional standards and does not provide any nutrition education. As a result of this, there is a low likelihood of lasting weight loss.
The Bottom Line: Simply stated , the Slim Fast diet is a waste of time. There are far better options, and those in pursuit of weight loss will ultimately be disappointment by the limited meal choices and weight regain once they leave the Slim Fast structure. Pursuing the Slim Fast Structure long-term would be nutritionally inadequate.