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Slim Fast, the famous slimming cure of the 90s

pack-slim-fast-regime-proteineSLIM FAST is a meal replacement product.

Losing weight fast while staying healthy is what overweight people want.

Manufacturers of slimming products have made no mistake, and the market is full of diet products, each more innovative than the last.

Meal replacement protein diets have been a big hit in the weight loss sector for many years. That’s why we’re taking a look today at a cure you’ve probably already heard of: Slim Fast.

Slim Fast presentation and promises

Slim Fast is a weight loss program based on high-protein meal replacements.

The 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. Our investigation will focus on the latter.

The Slim Fast program is extremely simple to follow. It comprises 3 key points:

  1. Replace 2 meals a day with a Slim Fast product (shake, smoothie or bar);
  2. Eat 1 balanced meal a day, with around 500 calories;
  3. Possibility of consuming up to 3 Slim Fast 100-calorie snacks in a day, to satisfy hunger between meals.

Meal replacements come in 3 forms: shakes, smoothies and bars. Each provides 20g of protein, 5g of dietary fiber and 1g of sugar.

Shakes are ready-to-use beverages, while smoothies take the form of a powder to be mixed with a liquid. The main flavors are creamy chocolate, strawberry and cream, vanilla cream and caramel latte.

Bars are available in salted butter caramel/almond, chocolate/cherry/cashew and dark chocolate/salt.

The 100-calorie snacks are chips in a variety of flavors, or sweet bites.

The website lets you calculate your BMI, and 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, so this product has been part of the slimming market for decades!

In the 90s, Slim Fast was a big hit in France, with TV commercials and products appearing on supermarket shelves.

Today, Slim Fast is no longer sold in France. In fact, the advent of other types of diet, as well as the arrival of more trendy protein diets, have succeeded in dethroning the product from its leading position.

However, Slim Fast is still available in the Netherlands, the USA and the UK, and of course on the Internet.

Slim Fast ingredients

Slim Fast products have a pretty mind-boggling list of ingredients! Take a look:
Water, Calcium Caseinate, Milk Protein Concentrate, Canola Oil, Cocoa (Processed with alkali), Maltodextrin, Cellulose gel, Natural and artificial flavors, Potassium Phosphate(phosphate de potassium), Mono and Diglycerides(mono et diglycérides), Glycerin(glycérine), Potassium citrate(citrate de potassium), Salt(sel), Soy lecithin(lécithine de soja), Sucralose(sucralose), Carrageenan(carraghénine), Sodium citrate(citrate de sodium), Citric acid(acide citrique), Caramel color(couleur caramel). Vitamins and minerals: Magnesium phosphate(phosphate de magnésium), Sodium ascorbate(ascorbate de sodium), Calcium phosphate(phosphate de calcium), Vitamin E acetate(acétate de vitamine E), Zinc Gluconate(zinc gluconate), Ferric Orthophosphate(orthophosphate ferrique), Niacinamide(nicotinamide), Calcium panthenate(acide panthoténique), Manganese Sulfate(sulfate de manganèse), Vitamin A Palmiate(palmitate de vitamine A), Pyridoxine Hydrochloride(pyridoxine hydrochloride vitamin B6), Thiamine Mononitrate(thiamine mononitrate vitamin B1), 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), Cholecalcifereol(cholecalciferol).

Note that the first ingredient is WATER! Next come whey proteins. These protein sources are recognized for their excellent quality, especially by athletes.

The high protein intake, combined with almost total elimination of sugars and fats, leads to ketosis, the basic principle of all protein diets.

The body manufactures ketone bodies and uses them as an energy source instead of glucose. This diet induces :

  • Low insulin levels, which lead to the breakdown of fat cells;
  • Increased glucagon levels, leading to increased glycogen release. As glycogen eventually runs out, the liver begins to use fatty acids to synthesize ketone bodies.

Protein-rich diets also have the capacity to increase the sensation of satiety, and therefore reduce calorie consumption.

In fact, a high protein intake produces an increase in glucose production in the small intestine. This spike in the liver signals the brain to eat less.

In the Slim Fast diet, the sensation of satiety is further enhanced by maltodextrin, a slow carbohydrate designed to satiate.

Finally, the composition is rich in vitamins and minerals of all kinds, not only to avoid deficiencies, but also to promote good protein assimilation.

Another advantage of proteins is that they help maintain muscle mass, while fat mass can melt away thanks to the reduction in calories.

Example of a balanced meal

Scientific studies on Slim Fast

We have identified several studies on this slimming cure.

One study compared the appetite-suppressant effects of Slim Fast with other types of food, and found that Slim Fast provided a longer feeling of satiety than comparison foods.

What’s important to say is that the foods in question were none other than 1 yoghurt, or 1 hamburger + soda, or 1 bagel + cheese + 1 orange juice. Nothing resembling a balanced meal!

What we can learn from this study is that, after taking Slim Fast, the first warning signals of hunger only appeared after around 5 hours.

(Source : Study Finds Slim-Fast Meal-Replacement Shake Controls Hunger Longer Than a Hamburger and a Soda ENGLEWOOD CLIFFS, N.J., Dec. 12 /PRNewswire-FirstCall/).

Another study, involving 97 women and 36 men following the Slim Fast program for 12 weeks, showed an average 10% loss 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 people with intolerances or allergies, Slim Fast products have no side effects or contraindications.

We do not recommend this type of diet for pregnant or breast-feeding women.

It should be noted that the significant reduction in caloric intake can, in the long term, slow down the metabolism, increasing the risk of weight regain.

Testimonials from Slim Fast users

According to Slim Fast users, meal replacements generally have a pleasant taste. However, many people find the satiety a problem, and indeed need to use the 100-calorie snacks, or decide to eat their evening meal very early, to make up for this disadvantage.

People who have used Slim fast also report a real psychological difficulty in eating only one real meal a day, as well as a lack of support for following this type of slimming cure.

Price and guarantee

It is not possible to order Slim Fast products on our websites. However, a list of the various websites where the products are on sale is available.

We have listed the price of a box of powder for 14 smoothies, i.e. a 7-day cure, at $10, i.e. approx. 8,50€.

The various sales sites do not offer a money-back guarantee.

Our opinion on Slim Fast

According to our survey, and our experience in testing slimming products, we don’t recommend this type of slimming cure.

Although weight loss can be achieved quickly, this type of diet offers no real support for changing eating habits, and therefore maintaining an ideal weight over the long term.

What’s more, the slower metabolism triggered by the radical reduction in calorie intake increases the risk of weight regain and the yo-yo effect.

Leave a Comment


  • Gaelle

    Avez vous testé chocolat slim merci pour vos tests

  • chatpitre69

    is there a product that helps you lose weight fast, effectively and without fuss?

    • Carl

      Losing weight is a global process that must be done with respect for time, your body’s limits and your metabolism.

      Rapid weight loss can harm your body and the likelihood of regaining the weight becomes very high.

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