SLIM FAST belongs to the category of meal replacements.
Losing weight quickly while maintaining good health is what any overweight person wants.
Manufacturers of slimming products have made no mistake about it, and the market is full of ever more innovative diet products.
Meal replacement protein diets have been a big hit in the weight loss industry for many years. That’s why today we’re reviewing a cure you’ve probably heard of: Slim Fast.
Presentation and promises of Slim Fast
Slim Fast is a weight loss program based on high protein meal replacements.
This program has been around for many years, and has released several versions of its famous diet.
Today, on the official website, it is possible to follow the Slim Fast protocol using Slim Fast Original products, or Slim Fast Advanced Nutrition products. It is on the latter that our investigation will focus.
The Slim Fast program is extremely simple to follow. It includes 3 key points:
- Replace 2 meals a day with a Slim Fast product (shake, smoothie or bar);
- Eat 1 balanced meal a day, with around 500 calories;
- Possibility to consume up to 3 snacks of 100 Slim Fast calories in total in a day, to satisfy hunger between meals.
Meal replacements therefore come in 3 forms: shakes, smoothies and bars. Each substitute provides 20g of protein, 5g of dietary fiber, and 1g of sugar.
Shakes are ready-to-use drinks, while smoothies come in the form of a powder to be mixed with a liquid. The main flavors are: creamy chocolate, strawberries and cream, vanilla cream, caramel latte.
The bars are available in salted butter caramel/almond, chocolate/cherry/cashew, dark chocolate/salt flavors.
The 100-calorie snacks are crisps with different flavors, or sweet bites.
The site, in English, allows you to calculate your BMI, as well as to see how many kilos you can lose, and in how long, with Slim Fast.
Slim Fast, the manufacturer
Slim Fast was created in 1977 in California, which means that this product has really been part of the slimming market for decades!
In the 90s, Slim Fast was a hit in France, and you could see its advertisements on television, and find its products on the first shelves of supermarkets.
Currently Slim Fast is no longer marketed in France. Indeed, the advent of other types of diets, but also the arrival of more trendy protein diets, have succeeded in dethroning the product from its leading position.
However, it is still possible to find Slim Fast in the Netherlands, the United States and the United Kingdom, and of course for sale on the internet.
Ingredients of Slim Fast products
Slim Fast products have a pretty mind-boggling list of ingredients! See instead:
Water(eau), Calcium Caseinate(calcium caseinate), Milk Protein Concentrate(milk protein concentrate), Canola Oil(canola oil), Cocoa (Processed with alkali), Maltodextrin(maltodextrin), Cellulose(cellulose gel), Natural and artificial flavors(natural and artificial flavors), Potassium Phosphate(potassium phosphate), Mono and Diglycerides(mono and diglycerides), Glycerin(glycerin), Potassium citrate(potassium citrate), Salt( salt), Soy lecithin (soya lecithin), Sucralose (sucralose), Carrageenan (carrageenan), Sodium citrate (sodium citrate), Citric acid (citric acid), Caramel color (caramel color). Vitamins and minerals(vitamins and minerals): Magnesium phosphate(magnesium phosphate), Sodium ascorbate(sodium ascorbate), Calcium phosphate(calcium phosphate), Vitamin E acetate(vitamin E acetate), Zinc Gluconate(zinc gluconate), Ferric Orthophosphate(ferric orthophosphate), Niacinamide(nicotinamide), Calcium panthenate(panthotenic acid), Manganese Sulfate(manganese sulfate), Vitamin A Palmiate(vitamin A palmitate), Pyridoxine Hydrochloride(pyridoxine hydrochloride vitamin B6), Thiamine Mononitrate( vitamin B1 thiamin mononitrate), Riboflavin(riboflavin), Chromium Chloride(chromium chloride), Folic Acid(folic acid), Biotin(biotin), Sodium Molybdate(sodium molybdate), Potassium Iodide(potassium iodide), Phylloquinone( phylloquinone or phytomenadione), Sodium selenite (sodium selenite), Cyanocobalamin (cyanocobalamin), Cholecalciferol (cholecalciferol).
Note that the first ingredient is WATER! Then come the proteins from the whey. These protein sources are recognized as being of excellent quality, especially by athletes.
The high protein intake, combined with an almost total elimination of sugar and fat intake, causes a phenomenon of ketosis, which is the basic principle of all protein diets.
The body makes ketone bodies and uses them for energy instead of glucose. This diet induces:
- Low insulin levels, which lead to the breakdown of fat cells;
- An increase in glucagon levels, which causes an increased release of glycogen. This eventually running out, the liver begins to use fatty acids to synthesize ketone bodies.
High-protein diets also have the ability to increase the feeling of satiety, and therefore reduce calorie consumption.
Indeed, a high protein intake produces an increase in the production of glucose in the small intestine. This peak felt in the liver sends the order to the brain to eat less.
In the Slim Fast diet, the feeling of satiety is even more favored thanks to maltodextrin, a slow carbohydrate which aims to satiate.
Finally, the composition is rich in vitamins and minerals of all kinds, not only to avoid deficiencies, but also to promote good assimilation of proteins.
Proteins have another advantage, that of allowing muscle mass to be maintained, while fat mass can melt away thanks to the reduction in calories.
Scientific studies on Slim Fast
We have found several studies on this slimming treatment.
Research compared the appetite suppressant effects of Slim Fast with other types of food, and found that Slim Fast provided a longer feeling of fullness than comparison foods.
What is important to say is that the foods in question were none other than 1 yogurt, or 1 hamburger + soda, or 1 bagel + cheese + 1 orange juice. Nothing like a balanced meal!
What we will retain from this study is that after absorption of Slim Fast, the first precursor signals of hunger only appear after about 5 hours.
Another study, involving 97 women and 36 men, following the Slim Fast program for 12 weeks, showed an average loss of 10% of excess weight.
(Source : Heber, David; Ashley, Judith M.; Wang, Hei Jin; Elashoff, Robert M., 1994: Clinical evaluation of a minimal intervention meal replacement regimen for weight reduction. Journal Of The American College Of Nutrition. 13(6): 608-614).
Side effects and contraindications of the Slim Fast diet
Apart from the presence of lactose and soy, which could cause problems for intolerant or allergic people, Slim Fast products have no side effects or contraindications.
We do not recommend this type of diet for pregnant or breastfeeding women.
It should be noted that the significant reduction in caloric intake can, in the long term, cause a slowing down of the metabolism, which increases the risk of regaining weight.
Testimonials from users of the Slim Fast cure
According to Slim Fast consumers, meal replacements generally taste good. However, many people complain about satiety, and actually need to use 100-calorie snacks, or decide to eat their evening meal very early, to overcome this drawback.
People who have used Slim Fast also report a real psychological difficulty in having only one real meal a day, as well as a lack of support to follow this type of slimming treatment.
Price and warranty
On the sites of Slim Fast, it is not possible to order the brand’s products. On the other hand, a list of the different websites where the products are on sale is available.
We have raised the price of a box of powder for 14 smoothies, i.e. 7 days of treatment, at the price of $10, i.e. approximately 8.50€.
The various sales sites do not offer a money-back guarantee.
Our opinion on Slim Fast
According to our investigation, and our experience in testing slimming products, we do not recommend this type of slimming cure.
Indeed, even if weight loss can be achieved quickly, this type of diet does not provide real support for modifying eating habits, and therefore maintaining an ideal weight over the long term.
In addition, the slowing of the metabolism caused by the drastic reduction in caloric intake increases the risk of weight gain and the yoyo effect.
Alternative to SlimFast
If you want to consult another test about an effective and serious slimming solution, I advise you to review the article below:
“PhenQ” is a slimming tablet that combines the positive slimming effects of several dietary supplements to achieve optimal weight loss!
See the analysis and testimonials on PhenQ!
Last update: September 14, 2022.