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SlimFast Review - Does This Meal Replacement System Work? Are poor taste and side effects deal breakers?

By Summer Banks on Sep 21, 2016
SlimFast Review

Convenience and efficacy are the two biggest factors in modern weight loss programs, and we’ve heard consumers discussing the pros and cons of Slim Fast for a while now. We decided to pick apart the ingredients, side effects, customer service and clinical studies. Additionally, we dissected hundreds of customer reviews and comments. Then we condensed and summarized to give you the information you need.


What You Need To Know

Slim Fast is a meal replacement shake containing fat free milk, water, sugar, cocoa, gum Arabic, calcium caseinate, cellulose gel, canola oil, potassium phosphate, cellulose gum, soybean lecithin, mono and diglycerides, artificial flavor, carrageenan, maltodextrin, and dextrose. Users are instructed to replace breakfast and lunch with these 11 oz. shakes and to supplement with a few small snacks. The shakes seem fairly portable, so the user can consume them at home, in the car, or at the office.

Slim Fast was introduced in 1977 and today is owned by Unilever. You can purchase Slim Fast from online retailers, although you can’t purchase the shakes directly from Slim Fast website. We like that Slim Fast is readily available and the longevity of the company, but read on…

Poor Taste – “Not the Best?”

The first concern about Slim Fast ingredients was taste. “Meal-replacement shakes are intended to substitute regular foods” said our Research Editor. “If the drinks aren’t flavorful, will you still want to use them?”

“I purchased Cappuccino Delight. Delightful it’s NOT. The taste reminds me of burnt coffee beans,” said one customer.

“Too much sugar, way too sweet and chocolaty. Does not feel like a meal,” said another user.

Side Effects – “Digestive Issues?”

As we read through more and more reviews, Slim Fast side effects was a concern. “It gave me gas and diarrhea. Never tried it again,” said a customer.

“The first gave me stomach pain. Within an hour the diarrhea began again,” said another. “18 grams of sugar – it is so sweet. It stays in your system for days,” commented a dieter.

Our research has shown that side effects can hamper the ability of a supplement to produce long-term results. If Slimfast casues slight digestive discomfort, a user is unlikely to stick with it.

The Science- “Any Proof?”

Slimfast does mention some studies relating to its effect on weight loss. Unfortunately, there’s no links to the information and we found that the parent company performed some of the tests. At DietSpotlight, we look for all of the research prior to making suggestions. If a company doesn’t offer science-based evidence, we become skeptical about it.

The Bottom Line – Does Slim Fast Work?

So, are you heading out to buy a case of Slim Fast? Well, we like the longevity of the company and that it seems affordable, but we’re hesitant about this one becuase of research isn’t readily available to customers. We aslo have concerns due to customer commenting about poor taste and some negative side effects.

If you still need to trim down a bit, we suggest going with a supplement with no mention of negative reactions and a formula containig some clincially-tested ingredients.

Among the best supplements we’ve come across in 2016 is one called Leptigen. It features a proprietary blend of four ingredients – some clinically-tested – which have been shown to help burn fat and boost metabolism. We can’t find talk of negative side effects and online reviews are showing customers seeing great results.

Better yet, the makers of Leptigen are offering a Special Trial Offer. It’s always a good sign when the makers of a product are willing to stand behind it.

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About the Author:

Summer Banks is an ISSA-Certified Fitness Nutrition Specialist and has reviewed over 2000 diet products. She has years of nursing training, experience as a manager responsible for 15 supplement brands, and completed coursework on Food and Nutrition from Stanford University. full bio.

How Does SlimFast Compare?

Previous SlimFast Review (Updated November 5, 2014):

What You Should Know

Slim-Fast is a well established company that has been around for many years. It produces a wide variety of products that range anywhere from shakes to candy bars. Claims have been made that these products can help you to lose weight by reducing your calorie intake, but providing you with the proper nutrition and vitamins that your body needs. It is said that Slim Fast is easy to follow and it won't make you hungry. We will now take a closer look so it may be determined if these claims hold any relevance.


The contents of Slim Fast Ingredients, in most of their products, are 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 dyglicerides, artificial flavor, carrageenan, maltodextrin and dextrose.

Product Features

Slim Fast does not appear to contain any special ingredients that really stick out as a "weight loss supplement". Basically, it is believed that the main purpose of the product is to make sure that your body is receiving the proper amount of nutrition by really making an attempt to include all of the daily dietary needs by combining the product with what Slim Fast likes to call "sensible meals". According to a source, you may be able to achieve these results by either using their products as a meal replacement, or by combining them with other foods that you may already have in your pantry or refrigerator. They recommend that you eat 2 meals a day that includes one of their products for each one, and one sensible meal at night with snacking in between. Of course, the snacks would also be Slim Fast products. It appears that Slim Fast's main goal may be to encourage you to eat less of regular everyday foods and replace them with Slim fast products. This will result in less food and less calories, but it may be delivering the proper amount of nutrition to your body while doing so.

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  • One advantage of this is that it appears that you still get to eat regular foods with the available meal plan system.
  • Slim Fast products can be found nearly anywhere from shopping centers to drug stores.
  • Slim Fast provides online support and helps to plan your menus


  • Most nutritionist may believe that this is not a long term solution to weight loss.
  • Nutritionist may also believe that the caloric intake is not enough.
  • It seems to contain too much sugar, probably resulting in an energy boost then a crash.
  • This does not appear to contain an effective metabolism booster.


Slim Fast appears as though it could be an effective weight loss regimen. However, there may be some concerns about the amount of sugar that is included in these products. These days manufacturers tend to put less sugar in products due to the crash and burn effects that it can have, especially when following a diet with such low caloric intake. Also, it may not be realistic to believe that this is a lifelong solution to weight loss due to the fact that someone simply may want to go their entire lives having to buy Slim Fast products in order to maintain their weight.

SlimFast Questions & Answers:

We read hundreds of customer reviews about Slim Fast and put them into this helpful FAQ.

What are the side effects of Slim Fast?

According to some customer reviews, Slim Fast side effects may include digestive discomfort, diarrhea, and stomach pain.

What are the ingredients in Slim Fast?

Slim Fast 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.

Does Slim Fast work?

Slim Fast is clinically proven to aid in weight-loss with regular use as part of a healthy eating program.

If you are looking for a supplement for weight-loss, you may want check out Leptigen. It’s backed by some amazing customer reviews.

How much does Slim Fast cost?

Slim Fast cost depends on the retailer, but for an 8-pack at Walmart, it costs about $9.98.

How should I take Slim Fast?

Slim Fast is a meal replacement shake, and it can be taken twice a day.

Can I take Slim Fast if I have a health condition?

As with any meal replacement or weight-loss supplement, you should consult your doctor before using Slim Fast, especially if you are pregnant, under 18 years of age, nursing, or suffering from any health condition.

What do users like about Slim Fast?

Slim Fast customers enjoy the weight-loss results with regular use.

What do users NOT like about Slim Fast?

Some customers of Slim Fast do not like the bad taste and it caused indigestion, according to reviews.

How do I contact the Slim Fast customer service department?

You can call Slim Fast at 1-800-754-6327. They also have various social media platforms you can contact them through.

What flavors does Slim Fast come in?

Slim Fast meal replacement shakes are offered in Creamy Chocolate, Strawberries and Cream, Vanilla Cream, and Caramel Latte.

Does Slim Fast offer other products?

Slim Fast as a brand does offer other products, including snacks, smoothies, and bars.

Does Slim Fast come with a guarantee?

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

Do you know of any special deals or discounts on Slim Fast?

No special deals or discounts are available for Slim Fast. If you are looking for a great deal on a great weight-loss supplement, you may want to give Leptigen’s Special Trial Offer a try. Customers love the results and the ingredients, something that is important to us. Click here to check it out.

35 User Reviews About SlimFast

Leave comments below
  • 1
    Harpers B

    I started using the product 2 weeks ago and so far I’m pleased with the taste and product price, I mixed it up with skim milk and slowly enjoyed my shake I also add some good protein to go along with my shake like a boiled egg, fresh fruit or 1/2 cup sugar free jello and so far I’m satisfied nutritionally. I’m glad it has helped me to cut down and out the late night fast food and walk and swim at my local gym, thanks slimfast I appreciate what the shake offers.


  • 2
    Nancy Davis

    ..I have been using your slim fast shakes for 15 years,but with your new Slimfast Advanced (11.01ozs) I can”t get it shook up after HARD shaking I still have lumps of shake mix left over


    Anna (Editor)

    Hi Nancy! For detailed product and usage instructions, please refer to the Slimfast official website for more information.


  • 3

    Why does it cause constipation?


    Adrian (Editor)

    Hello Carol. All users are different and can experience different side effects, but please make sure to consult with your physician before taking this product.


  • 4
    Your Name

    Slimfast makes me bloat. Equate brand doesnt


  • 5
    Your NamePeter

    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.



    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.


  • 6
    John Rupp

    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.



    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



    I meant drink lol ??


    Stephen (Editor)

    it can be taken twice a day.


  • 7

    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


    Stephen (Editor)

    Hey, Reema! We’ve not heard complaints of long term use, according to SlimFasts’ studies. If you are experiencing discomfort we suggest stopping and asking your doctor if these problems persist.


  • 8
    Connie Belt

    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


  • 9

    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.


  • 10

    nursing infants….good or bad?


  • 11
    John Frohock

    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.


  • 12
    Judith Rubiel-Perez

    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.



    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.


  • 13

    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.



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



    whats the name of this cheaper drink?



    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!


  • 14

    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.


  • 15

    How much sodiun is in a slim fast drink


  • 16

    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.



    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.


  • 17

    what happened when your menstrual cycle won’t for a month with slimfast


  • 18
    Betty Hamilton

    When will Slim Fast be back in Southfield Mi Or Liviona MI


  • 19
    Kelly Southard

    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.


  • 20
    Darlene Briggs

    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.


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