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SlimFast Review - 15 Things You Need to Know

SlimFast is a well-established line of meal replacement shakes and bars. The company claims that the current version of the product has been perfected following more than fifty clinical studies, offering more options than ever before. However, the SlimFast program works in conjunction with a sensible, calorie-restricted meal plan and regular exercise. There are many diet products that work well in tandem with calorie counting and a consistent exercise plan, and SlimFast products do not contain ingredients that are formulated to rapidly burn fat.

Nonetheless, our research team wanted to look into the current offerings to determine how they stack up. Read on to learn about the modern line of SlimFast options, and to get the Bottom Line on the product as a whole.

SlimFast can be purchased through their Official Site.

SlimFast Readers: Noom is offering our readers a free trial, for a limited time. Click here for this special offer!

What is SlimFast?

SlimFast is a weight loss program that supposedly makes it easy to lose weight. It provides different options. The SlimFast plan is not limited to a specific set of foods to consume. You can choose delicious food options that suit your preferences. It’s not just about eating fruits and vegetables or making do with shakes and smoothies.

This SlimFast review, by the way, is for the new system under a new administration. Unilever sold the SlimFast brand in 2014. With this transfer of ownership come some tweaks and improvements. This new system takes into account numerous clinical studies to improve the SlimFast diet plan with more diet choices.

As a branded weight loss method, the commercial aspect of it is noticeable. If you go to the website SlimFast.com, the official website of this weight loss plan, you will see not only diet plans and recipes but also for-sale products that are essential for you to follow the SlimFast diet plan.

NOTE: To avoid confusion, here’s a brief clarification. SlimFast is a brand name that refers to a diet plan and a range of products. If you want to do this weight loss plan, you will have to follow the SlimFast diet plan and purchase SlimFast products which include meal replacement shakes and smoothies as well as SlimFast snacks.


SlimFast Competitors

Other similar products: , Plexus XFactor, 18 Shake, 310 Shake

How Did SlimFast Start?

SlimFast is said to have been in practice for more than 40 years.

The SlimFast brand (diet plan and products), as mentioned earlier, used to be owned by Unilever.

At present, the company responsible for the development and manufacture of SlimFast products is KSF Acquisition Corporation located in West Palm Beach, Florida, USA.

We couldn’t easily find information about KSF Acquisition Corporation online. What we learned, though, is that this company is an investee of Kainos Capital, which acquired the SlimFast brand from Unilever back in 2014.

Slimfast claims


SlimFast Claims

The SlimFast plan promise is simple. It claims to provide significant weight reduction without having to get hungry and without having to struggle with tasteless meals.

It promises the shedding of pounds with one sensible meal for the day complemented by meal replacements and tasty SlimFast snacks. Moreover, it claims that results become noticeable in just one week.

As stated on SlimFast.com, you can achieve 50% more weight reduction by using the SlimFast diet plan as compared to reduced-calorie diets.


SlimFast Products And Ingredients

Here’s a summary of SlimFast’s products:

SlimFast Shakes

  • The shakes are individually bottled for ease of use
  • They are available in 5 flavors: Rich Chocolate Royale, French Vanilla, Strawberries & Cream, Cappuccino Delight and Creamy Milk Chocolate
  • The shakes contain 20 grams of protein, 5 grams of fiber, 19 grams of sugar, 1 gram net carbohydrates, and 24 vitamins and minerals.
  • Every bottle of the SlimFast shake contains the same amount of caffeine in a cup of coffee.
  • This new formulation (as compared to the Unilever formulation) is claimed to be 99.8% lactose-free.

SlimFast Smoothies

  • The smoothies are sold in mixes. The tubs provide enough product for approximately 12 smoothies
  • The smoothies come in 3 flavors: Vanilla, Creamy Chocolate and Mocha Cappuccino
  • Each smoothie serving contains 20 grams of protein, 5 grams of fiber and 24 vitamins and minerals.
  • Each serving provides the same amount of caffeine you can get from a cup of coffee.
  • The smoothies are gluten-free.

SlimFast Bars

  • These are available in multiple flavors: Peanut Butter Chocolate, Creamy Chocolate Mousse, Double Chocolate Cookie Dough, Whipped Triple Chocolate, Chocolate Chip Cookie Dough, Salted Caramel Macadamia Nut, Nutty Caramel and Nougat, and Whipped Peanut Butter Chocolate
  • Each pack contains 100 calories, 15 grams of protein, 5 grams of fiber, and 1 gram of sugar.
  • SlimFast bars are also meant to provide 4 hours of hunger control.

SlimFast Chips

  • These are available in two flavors: Sour Cream & Onion and Mesquite BBQ
  • Each pack contains 100 calories, 5 grams of protein, and 5 grams of fiber.
  • Each snack pack should keep hunger at bay for 4 hours.

Unfortunately, we couldn’t find information about the specific ingredients used in SlimFast’s products (shake, smoothie, and snacks). The only information available is that these products are gluten-free and high in fiber.

SlimFast also sells special lines of products, like:

  • SlimFast Keto
  • SlimFast Diabetic Weight-Loss
  • SlimFast Advanced Energy
  • SlimFast Advanced Nutrition

These product lines contain various powders, pre-made shakes, supplements, and more.

does Slimfast work

Does SlimFast Work?

When followed correctly, SlimFast does work. This structured diet program can deliver the weight loss it promises if you stick to how it’s meant to be used. However, the claim of losing weight without being mindful of the sizes of the portions you eat is not accurate.

SlimFast involves the reduction of the number of calories you take so you can’t just go on consuming delicious food without imposing limits.

Benefits & Results

SlimFast Benefits And Results

The SlimFast website features various testimonies from users of the SlimFast diet plan. These include male and female users. They claim to have lost weight in the range of 20 lbs. to 42 lbs. These user testimonials are posted on SlimFast.com.

The testimonials come with respective full names and brief backgrounds, making the testimonials appear to be more valid, and not mere fabrications.

For those who don’t have health issues but are trying to lose weight, SlimFast should be a compatible weight-loss option.

If you can handle a low-calorie diet, you should be able to follow the SlimFast diet plan.

However, it is recommended consulting your doctor first before committing to the SlimFast plan. This is particularly important for those who are taking medication for their conditions.

Slimfast and weight loss

Details On SlimFast And Weight Loss

There are no scientific or clinical studies specifically aimed at exploring the effectiveness of adopting a SlimFast only diet plan. However, the makers of SlimFast are citing a long list of research publications made to appear that they support the idea of using the SlimFast diet plan and SlimFast products.

We couldn’t find links to the specific research publications so we couldn’t ascertain if the research was conducted to prove or disprove the claims of SlimFast. The research appears to support health benefit potentials associated with SlimFast’s different components, not studies intentionally conducted to explore the effectiveness of SlimFast products.


How To Use SlimFast?

SlimFast is designed to enable a low-calorie diet that is easy to follow. Here’s a summary of how this diet plan works.

  • You will have to eat six times per day.
  • The six times include eating one sensible meal*, and two meal replacement** shakes or smoothies.
  • With the six times that you eat per day, you have to consume a total of 800 to 1,500 calories per day, well within the standard definition of a low-calorie diet.
  • Each SlimFast meal replacement shake or smoothie has about 120-130 calories.
  • Each SlimFast snack has 100 calories.
  • The amount of calories in the single “sensible” meal you eat for the day depends on liking. It could be from 500 to 1000 calories. You just have to avoid overeating for this meal.
  • In addition to eating six times a day, you also need to exercise for at least 30 minutes daily.
  • You also have to drink plenty of water (at least eight glasses per day).
  • Once you achieved your target weight, you can switch to having two sensible meals per day, and one meal replacement. The 30-minute daily exercise routine should also be maintained even after achieving your desired weight.

A sensible meal is one that is similar to what you have been used to eating before you started the SlimFast plan.

It should not be filled with comfort food but something that comes close to one of the meals you consume to achieve a balanced diet. For a guide on what a sensible meal is like, refer to the recipes on SlimFast.com.

SlimFast offers two types of meal replacements: shakes and smoothie mixes. The smoothie mix may be added to milk or other beverage. You need to make sure that the milk you use does not contain more than 50 calories. Otherwise, the calorie count for your smoothie replacement will be significantly raised.

SlimFast snacks can be 15-gram protein bars.

The standard SlimFast diet plan is mainly intended for women (1 meal + 2 meal replacements + three snacks). For men, SlimFast meal replacement and snack intake just need to be augmented to 200 calories.

This means that instead of using one scoop of the SlimFast meal replacement, two scoops will be needed (to get 200+ calories).

Instead of eating one energy bar or bar, for example, twice the amount will have to be taken.


The SlimFast Taste

SlimFast is touted as a diet plan that lets you eat delicious food. As such, it’s worth evaluating the taste.

In reality, it would be difficult to come up with a truly objective assessment of the taste of SlimFast products since taste is rather subjective. However, based on what users are saying, there are those who say that the meal replacements contain too much sugar.

Some say the coffee products seem to taste like they contain burnt coffee beans. Still, there are those who say that they like the taste of SlimFast products.

Perhaps, a more sensible way to put it is to say that SlimFast tastes just like how a typical diet would taste.

The adjective “delicious” as used in SlimFast’s marketing apparently refers to the standard taste anyone would expect in ordinary “delicious” food—that is sweet food should be sweet and savory should be savory.

SlimFast recipes, meal replacements, and snacks are not meant to cut down on sugar, salt, and other typical ingredients that create the flavor everyone is accustomed to.

The goal is more on controlling the amount and type of meal eaten. It’s also about choosing the right food to eat.

Side Effects

Potential SlimFast Side Effects

Like most other products, SlimFast is far from perfect. It is not free from side effects. Different people have different reactions to its products and SlimFast recipes.

Some users report having experienced diarrhea after using SlimFast products.

This is something that cannot be totally ruled out since too much consumption of protein does have adverse effects, one of which is diarrhea.

SlimFast promotes low-calorie intake, which may lead to minor side effects such as constipation, fatigue, and nausea.

It been reported that the use of sugar substitutes in the sugar-free versions of SlimFast shakes might cause gas build-up in the stomach and possibly diarrhea in some users.

To avoid the unwanted effects of imposing a low-calorie diet, you should consult a diet or health expert.

Product Warnings

SlimFast Product Warnings

As a low-calorie diet, it’s important to be aware that the reduced intake of calories may have an impact on blood sugar levels. It’s important to work with a nutritionist when trying any form of weight loss plan that involves alterations on typical food intake.

Additionally, a SlimFast diet may also interfere with medications. Adjustments may have to be made to avoid health problems or complications.

Low-calorie diets should only be adopted by those who have a BMI of at least 30. It is also not advisable for pregnant women and breastfeeding mothers.

SlimFast.com says that it is possible to drink alcohol while taking the SlimFast diet plan. However, alcohol can reduce the weight loss efficacy of this diet plan especially if you take in a lot of calories from mixers.

Any SlimFast Lawsuits?

We did not find lawsuits against SlimFast, at least for the new SlimFast under KSF Acquisition Corporation. Likewise, we didn’t find FDA advisories regarding SlimFast meal replacement and snack products.

What we found was an advisory for SlimFast Lipo Fast Burner Capsules Weight Loss for Men. This is apparently one of the products when the brand was still under Unilever.

The FDA advisory warns that SlimFast Lipo Fast Burner is not a registered product and has not undergone the evaluation of the agency. The public is hence advised not to buy it.

Since the SlimFast products available on the SlimFast.com website don’t include the products mentioned in FDA advisories, it’s safe to say that there are no health risks or concerns reported regarding them.

SlimFast Alternatives

If you don’t like the taste of SlimFast’s meal replacements or you can’t handle the system it imposes, you can try other weight loss plans. Similar products include:


This is a comprehensive low-calorie diet plan (about 800 calories per day) that also involves the use of meal replacements. However, it’s not something you can do on your own like SlimFast. The plan entails medical supervision as well as counseling and lifestyle education. You will also have to take in vitamin and mineral supplements following the Optifast plan.


If you prefer something that affords greater flexibility, Medifast is something you might want to consider. It lets you choose a plan that involves 4 Medifast meals (meal replacements), 2 self-prepared meals, and 1 healthy snack. This plan lets you consume around 1,300 calories per day.

DIY Shakes And Snacks

SlimFast is mainly about taking a low-calorie diet by substituting two of your three meals for the day with meal replacement (shakes or smoothies) and eating three snacks (for the day) with 100 calories each.

If you are not fond of the taste of SlimFast’s meal replacements and snacks, you can just create your own. You just have to make sure you get enough nutrition with them and that they are around 100 calories each.

Recommended ingredients would include lactose-free yogurt, non-fat milk, raw cacao powder, flaxseed, various berries, peanut butter, and unsweetened almond milk.

What Users Are Saying

“It’s regular Slimfast – which I have used in the past to get my weight back under control. The negatives are that you really need a blender (I use a stick blender) to mix this well enough that you don’t get a clumpy mess. Also, there is just the very slightest of a chalky undertaste. Not bad but there. I know that a lot of people knock Slimfast for how sweet it is, but I have used it more than once in the past with good results. I take prednisone periodically to treat a chronic illness and it brings the weight on like crazy.”

“I use Slimfast to lose weight and to maintain my weight.”

“I’ve had watery bowels for 36 hours after drinking only 3 shakes! In between running to the bathroom, I’ve only been able to eat slices of bread and take small sips of electrolyte water! I’ve lost 4lbs so far, just not how I imagined!”

Bottom Line

The Bottom Line on Slim Fast

So, are you heading out to buy a case of SlimFast Advanced Shakes? Well, we like the longevity of the company and it’s affordable, but we’re hesitant about this one because the research doesn’t directly link it to weight-loss, there are no dedicated peer-reviewed studies and elements in the formula that could disrupt or slow the digestive process, like fiber, to reduce hunger and slow the onset of appetite are missing. We’re also concerned about the fact that beverages are not as effective as solid foods in terms of satiety.

Do you want to trim down a bit? If so, we suggest going with a program that’s backed by clinical research – we just tend to err on the side of our scientific research.

Among the best products we’ve seen this year is one called Noom. It features personalized, custom meal plans, expert articles and resources, food tracking, exercise tracking and more. There’s even human coaching. We’ve found some pretty amazing user reviews and customer service rocks.

Also, the makers of Noom are so confident in their program, they’re offering a free trial to Dietspotlight readers.

Learn More About Noom »
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What are the side effects of drinking Slim Fast?

SlimFast side effects may include digestive discomfort, diarrhea, and stomach pain.

What is SlimFast made of?

SlimFast ingredients include fat free milk, water, sugar, cocoa (processed with alkali), gum Arabic, calcium caseinate, cellulose gel, canola oil, potassium phosphate, cellulose gum, soybean lecithin, mono and diglycerides, artificial flavor, carrageenan, maltodextrin, and dextrose.

How much is a can of Slim Fast?

At most retailers, you can purchase eight shakes for $10, which means that each can is $1.25.

Where to buy SlimFast?

SlimFast products are available in various retail stores like Walmart, CVS, Kmart and Walgreens. You can also find it in some convenience stores, according to SlimFast reviews.

How many Slimfast shakes a day?

SlimFast meal replacement shakes are suggested twice daily when following the diet plan. However, depending on your caloric needs, this may be different for you. Ultimately, the idea is to burn more calories than you take in to lose weight.

Where can I buy SlimFast?

SlimFast can be purchased using their Official Site.

Do the Slim Fast shakes really work?

Slimfast provides an easy way to meet calorie goals for the day. By controlling portion size and limiting caloric intake, you can lose weight and keep it off.

Who came up with Slim Fast?

Slimfast was first released by the Thompson Medical Company in 1977.

Does SlimFast come with a guarantee?

SlimFast may come with a guarantee, depending on the policies of the retailer it is sold at.

Are Slim Fast shakes vegetarian?

SlimFast does offer some vegan products.

How do you make a Slim Fast shake?

You can put one scoop of the SlimFast mixture and mix it with at least 8 ounces of whatever fluid of your choosing.

How long does it take to lose weight on Slim Fast?

It can take between 8-10 weeks to see significant weight loss with SlimFast.

How much water should you drink on Slim Fast?

Users should drink at least 2 liters of water while using SlimFast products.

Is Slim Fast keto approved?

SlimFast does have a line of keto approved products.

27 SlimFast Reviews

  • SlimFast
    Your NamePeter (Verified Purchase)

    Just started with slimfast and it seems to be working, lost 3 lbs in 2 weeks , but it may have had cause of irregularity, do not know if any one else has had the same problemTell us your thoughts about SlimFast.

    • christine

      Tried slim fast in the part. What l found is losingtje natial way.you can easily. Weight more weight by eating less. Excefcisingmore. For now my excerise is mainly walking for an hour. Not leisure. Walk more like brisk. Walking. I lost 3 pounds in a week.. so can too without slimfast diet.

  • I have no problem with the Slim Fast
    John Rupp (Verified Purchase)

    I have no problem with the Slim Fast diet program. I have lost almost 25 lbs. I plan on staying with it for another 5 lbs.I been losing 8-10 lbs per month. Plus have not had any health issues.

    • Alyssa

      How does it work? Do you drunk all day long? I plan on trying it since I just had another baby almost 9 months ago and I wanna get my old body back soon real soon cab you please help I would be greatly appreciative and thankful

      • Alyssa

        I meant drink lol ??

  • I am not sure
    reema (Verified Purchase)

    It is about 5 days now I started taking slim fast shake.i have severe gastric problem. But I am not sure it is because of this product.i wanted to know if I consume for long term, is there any health issues with this product. Thanks

    • Glenn (Editor)

      Hi Reema. Considering you mentioned you experience severe gastric problems, you may want to reach out to a healthcare professional. However, the one we’re keeping our eye on is Dietspotlight Burn. It contains ingredients backed by science and customers aren’t talking about harmful side effects. Click above to read about the sample offer.

  • mix the powder myself
    Connie Belt (Verified Purchase)

    My thoughts are, that i can never find French Vanilla on the shelves at Walmart in Paducah, Ky. I love this product and it is very frustrating not to be able to find it!! I even went on line to purchase it and they were sold out! But last week they had it, but was only going to let me buy 2, when I was wanting 10 cans. I like the powder so I can mix it myself. Thank you for listening. Connie Belt

    • Your Name

      ITell us your thoughts about SlimFast I’m very overweight ,want lose 70 lb so going give it ago I love the coffee latte which sells out fast in UK. Read all comments which find helpful thankyou and good luck to all xx

  • I will quite SlimFast immediately.
    maby (Verified Purchase)

    slim fast contain to much sugar I start to take tons of water after using this product for one month .I will quit it inmmediately.

    • Ana

      I started taking the slim Fast shake Friday and Saturday morning, but had to stop it Saturday, made me feel so bad that i couldn’t stand all day, nausea, headache, been sick all day Saturday and Sunday. Had to stop it.
      Never gonna take it again, If anyone is thinking about having it, think and search before doing it.

  • Disappointed with the plastic bottle
    John Frohock (Verified Purchase)

    I have been a long time user of slim-fast shakes. Today I am quitting. The reason is inconvenience of the new plastic bottles. I use to have my shake on the run. Pop the top and drink it on the drive to work. Now I have to remove the cap, remove the aluminum foil and figure out a place to put them while I drink my shake. The top of the bottle feels funny when drinking from it, and the bottle is to small; falls over in the cars’ cup holder. Looks like the price went up when you shifted to plastic as well. I’m dissapointed.

  • Questions about pricing and packaging
    Judith Rubiel-Perez (Verified Purchase)

    I went to the pharmacy to pick up meds and slimfast and was shocked at what I saw. Now your company is cheating us out of your product. I use to get a 12 pack now its an 8 pack. It use to be 11 ounces, now its 10 ounce. The 6 packs are now 4 packs for the same price. What the heck is going on? I feel your company is starting to screw the consumer. Does your company think that us consumers are stupid, do you think just because you put your product into a plastic bottles that we well be happy? Not me.. If your going to give us the same amount in your plastic bottles then fine and dandy, but don’t take away the volume. I think you need to talk to your marketing dept or your CEO and tell them that the public is not happy. The sales person said she had several complaints since your product hit the shelves. Its bad enough our gas and cost of living is going up, and now the one thing I felt I could afford to help me with my weight problem has gone up. I think you need to do some changes before people start to boycott your product…A concerned consumer.

    • david

      I agree with your comment. I will go to another brand. It is the price. slimfast take note, the price would usually be around $1.00 a can. the price per can has now gone up 40%. I don’t need that headache.

  • it's really expensive

    At 7 or 8 dollars for a 6 pack, it’s really expensive. I found some shakes at Aldi that taste just like them, same vitamins, less calories, and it’s 2.99 for a six pack on sale. Regular price is 4.29.

    • Mae

      What’s the name brand and do they offer a powder you can mix because I am lactose intolerent?

    • cass

      whats the name of this cheaper drink?

    • Jennifer

      I was wondering if Aldi had something like it. I just started the Slimfast diet and really like it, but was wondering if there was a cheaper version. Thank you for letting us know. I will get Aldi’s from now on. It’s my favorite place to grocery shop anyway!

  • it's good product
    Fion (Verified Purchase)

    I do love this program, it’s worked for me, and I continue exercise 3 times a week,also control myself do not eat after 6 pm. avoid from sweet. it’s good product.

  • Slimfast
    lynn (Verified Purchase)

    Slimfast worked for me. i lost 3 lbs in the first week on the 3-2-1 plan & still losing about 2 lbs a week.

    • Shelly

      Hey , you said you lost 3 lbs the first week. I was wondering how much exercising your doing with the diet to get those results, and what exercises are you doing? I wanted to try the SlimFast 3-2-1 Plan, but I wasn’t completely sure if it worked. Thanks.

  • All Slim Fast shakes in a can from 2009 have been recalled.
    Kelly Southard (Verified Purchase)

    Yes, I would throw them away. All Slim Fast shakes in a can from 2009 have been recalled. The powder and slim fast bars are ok. It’s just the cans.

  • My brother said That I should throw this away as it had been recalled. Is this correct?
    Darlene Briggs (Verified Purchase)

    i have 3 six-packs of Slim Fast Diet Drink that I purchased in 2009. My brother said That I should throw this away as it had been recalled. Is this correct? Please advise.

    • Lawrence Smith

      Hello: I read your article on the ingredients in slimfast. For five years I have been using slimfast once a day in the morning. I usually mix a quart bottle in the night and it last about two days. During this five year period I had colitis of the stomach. Only recently did I hear that these problems can be caused by diet. I decided to eliminate foods form my diet to see what could be causing the colitis. I got down to milk and slimfast. When I stopped drinking milk with slimfast my symptoms finally went away. I thought at first it was the lactose, so I went for several days without any milk or slimfast, the symptoms are gone. They I started to see if I could drink milk with no lactose. For several days the symptoms have still been gone and I dont have to take the medicine which cost me $100 a month any longer. I believe the slimfast has been causing me colitis all these years. I am still off the medicine and slimfast and wont use the product any more. I would like to tell other people who may have colitis about this problem. Can you suggest places I can contact? Thanks very much Lawrence Smith

      • Htay RN

        Lawrence, colitis of the stomach?? Colitis refers to the colon and has no referal to the stomach. Slimfast is not intended to be used “for five years” And a quart lasted you two days? That’s two servings you were drinking for one breakfast. With this is mind, I question your ability to mix the proper concentration. Don’t slam the product if you are not follwing direction of proper use.

      • Kelly

        I used slim fast once a day for three days and ended up dehydrated. I drank a ton of water and even ate balanced meals. My stomach didn’t agree with the slimfast and I am not lactose intolerant. Slim fast also is the cause of my immune system crashing. I ended up with bloating and gas. Slimfast was the only thing I did differently. I went to my doctor and she claimed slimfast is not good for anyone. I didn’t read the ingredients until after I took it to my doctor. There is way too much sodium. My doctor said that’s why I was suddenly dehydrated. For me to cut it out of my diet altogether!!! Now that I have, I feel so much better! Also slimfast claims it curves hunger. I call BS. I WAS SO HUNGRY THAT I ATE more than I ever did. I think I ll stick to my regular diet instead of slimfast!!!

    • Glenn (Editor)

      Hi Darlene. Considering the date on the bottles is 2009, they may be out of date. As a replacement, there’s one that we’ve been hearing buzz about and it’s Dietspotlight Burn. It contains clinically-tested ingredients and customers are sharing positive results. Click above to read about the sample offer.