Does the Slim Fast Optima Diet Really Work?

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Slim Fast is one of the few weight loss programs that have been clinically studied.

One study that examined if Slim Fast works was conducted in the Obesity Center at the University Hospital of Ulm in Ulm, Germany, in 1999. The study, designed to test whether an energy restricted diet combined with the meal replacement Slim Fast is a useful tool for sustained weight loss, clearly found that Slim Fast can be used successfully for long-term weight control and improvements in biomarkers of disease risk.

Can I lose weight drinking Slim Fast? - The Study Design

The 100 participants in the study, all over 18 years of age with Body Mass Index (BMI) between 25 and 40, were prescribed a balanced diet of 1200-1500 calories per day. They ate three meals (breakfast, lunch, and dinner) and two snacks each day, with 19-21% of their daily calories coming from protein, 48-54% from carbohydrates, and 25-34% from fat.

The study was divided into two phases:

Phase 1
During Phase 1 – three months of weight loss – participants were randomly assigned to one of two groups.

For the 50 participants in Group A (the control group), the balanced diet outlined above (3 meals and 2 snacks) was composed of conventional foods that the participants selected themselves.

For study participants who were assigned to Group B (the Slim Fast users), the prescribed diet was changed to replace 2 of the main meals with Slim Fast meal-replacement shakes, soups or hot chocolate, and the two snacks were replaced with Slim Fast nutrition snack bars.

Phase 2
Both groups were prescribed the same diet during Phase 2, a 24 month period of weight loss and weight maintenance. All study participants were prescribed the same number of calories, and all were instructed to replace one meal and one snack with the energy-controlled and nutrient dense Slim Fast replacements.

How Much Weight Will I Lose on Slim Fast? - The Results

Phase 1
After Phase 1, participants in Group A (the control group) had lost an average of 1.3 kg, while those in Group B (the Slim Fast group) had lost an average of 7.1 kg! For men, the difference was 1.1 kg in the control group versus 8.4 kg with Slim Fast; for women 1.2 kg in the control group versus 6.8 kg with Slim Fast.

What does Slim Fast do? It Reduces Your Hunger by 19%

When food intake before and after Phase 1 was compared, it was obvious that the participants in the Slim Fast group saw a greater decrease in calorie consumption. They ate less food.

Group A's calorie intake decreased from a baseline of 1797 cal/day to 1663 cal/day, while Group B's (the Slim Fast group) decreased from 1814 cal/day to 1475 cal/day – an astounding 19%!

Fat intakes saw a similar decrease, with Group A going from a baseline of 37.6% to 32.9%, and Group B from a baseline of 36% to 26.4%.

This significant difference between the control and Slim Fast groups suggests that Slim Fast decreases cravings and suppresses appetite.

Will Slim Fast Lower My Disease Risk as Well as My Weight?

Women in Group A lost some weight (although only 1/5 of that seen in Group B), but they did not show any improvement in key biomarkers for disease risk, with the exception of a slight decrease in serum cholesterol. Men in Group A saw no significant weight loss and no change in biomarkers for disease risk.

In contrast, both men and women in Group B, the Slim Fast group, experienced significant weight loss as well as changes in key biomarkers for disease risk. They showed improvement in plasma triacylglycerol, blood glucose, and insulin concentrations, as well as a significant improvement in systolic blood pressure.

The Results: Phase 2

After completing the 3-month Phase 1, participants entered the 24-month Phase 2. During Phase 2, both groups followed the same dietary plan, replacing one meal and one snack with Slim Fast products.

During these 24 months, both groups lost weight at a rate of .07% of their initial body weight per month. Group B, which used Slim Fast for the additional 3 months of Phase 1, lost and maintained an average of 5.34% more of their body weight than Group A. It should also be noted that concentrations of serum triacylglycerol (a biomarker for disease risk) decreased significantly in both groups during Phase 2 (from 2.13 to 1.77 mmol/L in Group A, and from 2.23 to 1.4 mmol/L in Group B).


What is important about this study is that although both groups consumed the same amount of calories, the Slim fast group lost more weight.

At the end of Phase 1, there was a highly significant difference between groups in terms of percentage weight changes: Group A (control group) saw a decrease of approximately 1.5% of initial body weight, while Group B (Slim Fast group) saw a much larger 7.8% decrease. At the end of Phase 2, participants in Group A had lost 5.9% and those in Group B 11.3%.

This study's comparison of energy-controlled meal and snack replacements (specifically Slim Fast) with a standard weight loss diet clearly showed that the group using Slim Fast lost significantly more weight than those following the standard diet, despite both groups being prescribed the same energy intake.

When all participants followed the same diet during Phase 2, replacing one meal and one snack with Slim Fast products, the rate of weight loss in the control group caught up with the Slim Fast group. Both groups maintained their average weight loss and lost additional weight over the following 2 years.

The weight loss results of the study's two year dietary intervention were comparable with those of drug treatment, but without the adverse events associated with such treatment and with only minimal and transient gastrointestinal side effects. Participants who used Slim Fast for both Phase 1 and 2 even attained the 8% weight loss standard that was recently established for dietary management of obesity with low-energy diets.

In addition to significant weight loss and improvement in biomarkers of disease risk, benefits of meal-replacements such as Slim Fast include convenience, low cost, and a minimal need for professional intervention. Long-term dietary interventions using Slim Fast or other meal replacement products are an effective way to improve weight control and lower disease risk among obese patients.

So, Does Slim Fast Work?

It depends. The study shows that if you use Slim Fast products as meal replacements along with a low-calorie diet, you can potentially lose more weight than if you eat only conventional food. I have met people who said they lost weight thanks to Slim Fast. For a review of Slim Fast Optima click here.

Where to Buy Slim Fast Cheap?

You can buy Slim Fast Optima at a discount from Amazon.

About the price

Hi i am monisha Jude. I want to buy this product. Can you pls tel me the price. I am from Bangalore India...

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