Updated: 01/10/2017 - Site operated by Leptigen
By Summer Banks Dec 14, 2016

Why are people talking about SlimFast? Our attention turned toward ingredients, side effects, clinical research, peer-reviewed studies and customer service quality. Additionally, we dissected hundreds of dieter reviews and comments to see if anyone was successful in reducing caloric intake and weight. Then, we condensed and summarized to give you the information you need.

SlimFast Readers: Click here to find out why we're giving away samples of our product, Leptigen.

What is SlimFast?

First off, SlimFast is a meal-replacement system offering ready-to-drink shakes, 100-calorie snacks and nutrition bars. The ingredients include amorphophallus konjac [1], rhizome, apple pectin, oat fiber, fat free milk, water, sugar, gum arabic, canola oil, milk protein concentrate, cellulose gel, coffee powder, mono and diglycerides, potassium phosphate, hydrogenated soybean oil, natural and artificial flavors, maltodextrin, dl-alpha-tocopheryl acetate, phytonadione, thiamine mononitrate [2], riboflavin, niacinamide, pyridoxine hydrochloride, and folic acid. You’ll replace one meal and incorporate a snack as needed, ideally to curb appetite and keep blood glucose level between meals.

SlimFast was introduced in 1977. The official website and local grocery stores sell the product line. The longevity of the company and the affordability are positives, but read on…

Poor Taste – “Is it Flavorful?”

The first concern about SlimFast ingredients is taste. “Meal-replacement shakes [3], nutrition bars and snacks are intended to substitute regular foods,” said our Research Editor. “If the dieter doesn’t like the flavor, that is more than enough to keep them from sticking with the SlimFast products. If you don’t maintain a reduced-calorie diet, you are less likely to shed weight.”

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

“Too much sugar [4], way too sweet and chocolaty. Does not feel like a meal,” said another user.

On the other hand, we found SlimFast reviews that didn’t mention poor taste.

“Fills me up and tastes good,” reported a dieter.

SlimFast Side Effects – “Digestive Issues?”

As we read through more and more reviews, SlimFast side effects were a concern. “It gave me gas and diarrhea. [5] Never tried it again,” said a customer.

“The first gave me stomach pain. Within an hour the diarrhea [6] began again,” said another.

While SlimFast side effects were a concern for some, others didn’t mention adverse reactions.

“No gastrointestinal issues to speak of,” reported a customer.

“There’s no effects on my digestive system [7],” stated another.

Our research has shown that it often takes a tiny thing, like SlimFast reviews talking about side effects, to slash the dieter’s chances of success. If Slimfast meal replacement shakes do cause some stomach or digestive issues, that could be an issue.

The Science- “Any Research Behind the Shake?”

SlimFast does mention some studies relating to its effect on weight-loss. There’s even scientific evidence supporting using meal replacements to cut calories. Unfortunately, when we searched PubMed and various medical journals, we were unable to find any peer-reviewed studies to prove it works. It does contain protein and human studies have shown it to “[induce] sustained reductions in appetite.” [8] We’d like to see a little more soluble fiber, as that ingredient can slow the digestive process. [9]

At DietSpotlight, we look for solid science. When there’s no clear link to clinical studies, we get concerned. We’ve found far too many readers asking, SlimFast – does it work? We’d really need research to say yes, as it pertains to this specific brand.

The Bottom Line – Do SlimFast Products Work?

So, are you heading out to buy a case of SlimFast meal replacement? 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. [10]

Do you want to trim down a bit? If so, we suggest going with a supplement with a formula containing clinically tested ingredients shown to help promote weight-loss. It’s not that we’re putting down SlimFast products, we just tend to err on the side of our scientific research.

Among the best products we’ve seen this year is one called Leptigen. It features four clinically-tested ingredients which have been shown to help accelerate metabolism, ignite fat loss and fight hunger. We’ve found some pretty amazing user reviews and customer service rocks.

Also, the makers of Leptigen are so confident in their supplement, they’re offering a Special Trial Offer.

Previous SlimFast Review (Updated November 5, 2014):

What You Should Know About Slim Fast

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. You can find 100-Calorie Snacks, Meal Replacement Shakes and Smoothies and Eat Less Pills on their website. 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. Easy to follow, Medifast is an alternate weight-loss program that offers specific foods to be consumed on a regular basis that include soups, entrees, bars, shakes in a four day meal plan.

Slim Fast Ingredients

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.

Slim Fast 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". Similar to these sensible meals, Shakeology is a line of meal-replacement shakes high in protein discovered to reduce cravings. Although these proteins shakes are found to support a high supply of protein, the side effects still cause a concern for negative reactions. According to a source, you may be able to achieve these results by either using Slim Fast's 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 two meals a day that includes one of their products for each one, and one sensible meal at night with snacking in between. As it pertains to appetite suppressants, a good source for weight loss can be found in caffeine, one in particular product that resembles same results is Hydroxycut. Needless to say, this thermogenic can be taken once or twice a day, like Slim Fast. Caffeine is found to coincide with with healthy weight loss by suppressing the appetite and increasing energy levels. Of course, their 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 stimulant will result in less food and less calories, but it may be delivering the proper amount of nutrition to your body while doing so. You can find identical results in PhenQ affirming the supplement elevates energy levels with it's secret ingredient, caffeine.

Advantages of Slim Fast

  • 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

Disadvantages of Slim Fast

  • 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 SlimFast meal replacement and other SlimFast products and put the most common questions into this helpful FAQ.

What are the side effects of SlimFast?

According to some customer reviews, SlimFast side effects may include digestive discomfort [1], diarrhea, and stomach pain.

Can Slimfast give you diarrhea?

We didn’t find any specific ingredients in Slimfast products that are associated with diarrhea, but some users have reported this side effect.

What is SlimFast made of?

SlimFast ingredients include fat free milk, water, sugar, cocoa (processed with alkali), gum Arabic [2], calcium caseinate, cellulose gel, canola oil, potassium phosphate, cellulose gum, soybean lecithin, mono and diglycerides, artificial flavor, carrageenan, maltodextrin, and dextrose.

Does SlimFast work – how effective is SlimFast?

SlimFast meal replacement shakes are not directly clinically tested or proven, but research shows meal replacements, in general, can help reduce caloric intake. So, how good is SlimFast for weight loss? It’s likely as effective as other options that offer protein, fiber and vitamins in a shake (or snacks/foods).

How much are SlimFast shakes? 

SlimFast cost typically ranges from around $5 to more than $15, depending on the SlimFast products and quantities.

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 times can I drink SlimFast in 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.

How do you make SlimFast?

Many of the SlimFast products are ready-to-eat/drink. But, there are some powders out there that can be mixed with water, juice or milk. To reduce the total number of calories, you can use almond, soy or coconut milk with your SlimFast meal replacement shakes.

Is there gluten in SlimFast?

The description for SlimFast meal replacement shakes say they are gluten-free. We didn’t see the same claim in any information on the snacks and other foods.

What does SlimFast taste like?

Some SlimFast reviews claim the meal replacements taste a little gritty or powdery. However, there are an equal number of reviews talking about how good SlimFast products taste – so it looks like it’s 50/50.

What flavors does Slimfast have?

As of early 2017, Slimfast meal replacement shakes were available in Creamy Chocolate, Vanilla Cream, Strawberries & Cream, Caramel Latte and Mocha Cappuccino.

Can I take SlimFast if I have a health condition?

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

What do users like about SlimFast?

SlimFast customers enjoy the weight-loss results with regular use.

What do users NOT like about SlimFast?

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

How do I contact the SlimFast customer service department?

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

What flavors does SlimFast have?

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

Does SlimFast offer other products?

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

Does SlimFast come with a guarantee?

SlimFast 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 SlimFast?

No special deals or discounts are available for SlimFast. 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.

SlimFast Scientific Abstracts:

Soy Protein

Soy protein consumption was linked with changes in serum LDL cholesterol levels of -0.23 mmol/l (95% confidence interval, -0.28 to -0.18 mmol/l) or a decrease (5.5%) in comparable research and -0.16 mmol/l (95% confidence interval, -0.22 to -0.11 mmol/l) or a decrease (4.2%) with crossover studies (p < 0.001 parallel versus crossover). Net serum HDL cholesterol levels were 3.2% greater (p < 0.007) in parallel studies with soy in comparison to control. Fasting serum triacylglycerol levels were lower (10.7%) for soy in comparison to control (p < 0.008). In conclusion, soy protein intake of 30 g per day was linked with substantial improvement in lipoprotein risk factors for coronary heart disease. In comparison with crossover randomized clinical trials, parallel randomized clinical trials had substantially higher quality grades and were linked with greater improvements in serum LDL cholesterol. Intake of 1 to 2 servings of soy protein every day has substantial positive effects on serum lipoprotein risk factors for cardiovascular heart disease. [1]

Vitamin B12

In some individuals, cognitive function quickly declined at younger ages, yet stayed intact within others until older ages. Using multivariate regression analyses, following adjustments for risk factors, the concentrations of vitamin B12 holotranscobalamin, total homocysteine, and methylmalonic acid showed a cognitive decline, while folate did not. Doubling concentrations of vitamin B12 holotranscobalamin (from 50 to 100 pmol/L) was linked with a 30% cognitive decline (−0.137 to −0.083). Doubling total homocysteine from 10 to 20 μmol/L or methylmalonic acid from 0.25 to 0.50 μmol/L was showed to have a cognitive decline of 50%. Following adjustments for every vitamin marker at the same time, the links of cognitive decline with methylmalonic acid as well as vitamin B12 holotranscobalamin remained substantial. [2]


Consumption of dark chocolate (cocoa products) substantially decreased serum low-density lipoprotein and total cholesterol levels (mean differences (95% confidence interval) were −5.90 mg/dl and −6.23 mg/dl. There were no statistically important effects noticed for high-density lipoprotein (mean differences (95% confidence interval): −0.76 mg/dl (−3.02 to 1.51 mg/dl)) as well as and triglyceride (−5.06 mg/dl (−13.45 to 3.32 mg/dl)). The data is consistent with the helpful traits of cocoa products on total and low-density lipoprotein cholesterol and no significant effects on high-density lipoprotein and triglyceride within short-term intervention trials. [3]

Gum Arabic

Before and after analysis in the group displayed substantial decreases in body mass index by 0.32 (95% confidence interval: 0.17 to 0.47; P<0.0001) as well as body fat percentage by 2.18% (95% confidence interval: 1.54 to 2.83; P<0.0001) after consumption of 30gm per day Gum Arabic for a period of 6 weeks. Participants experienced side effects of the Gum Arabic only during the first week. In conclusion, Gum Arabic was the cause of a substantial decrease in body mass index and boy fat percentage in the healthy adult females. These effects could be helpful in the treatment of obesity. [4]

Slim Fast meal replacements shakes and products claim to help with weight loss by helping control caloric intake.

SlimFast Ingredients and Supplement Facts

Serving Size: 1 bottle
Serving Per Container:
Amount per Serving % DV
Fat free milk *
Water *
Sugar *
Canola oil *
Maltodextrin *
Milk protein concentrate *
Cellulose gel *
Cellulose gum *
Natural & Artificial flavors *
Mono & diglycerides *
potassium phostate *
soy lecithin *
Calcium phosphate *
Carrageenan *
Sucralose potassium *

Other Ingredients: None

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About the Author:

Summer Banks, a content strategist at Leptigen, has researched over 5000 products in the past 10 years. 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.

Rating: 3.6. From 30 votes.
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User Comments

37 Comments on "SlimFast Review"


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I absolutely love Slim Fast! I have tried several things to loose weight and nothing has worked for me. I started slim fast 5 weeks ago and have lost 11 pounds and several inches. It taste great to me. I have a morning shake, morning snack, lunch shake, afternoon snack and eat a regular dinner. I drink 5 bottles of water a day and do not work out. It has been the best thing for me.

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.

Hi Harpers. Good job on making those changes. If you want to boost those results, you may want to consider adding Leptigen. Click above to read about the sample offer.

..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

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

Why does it cause constipation?

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.

Slimfast makes me bloat. Equate brand doesnt

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.

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 ??

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

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 Leptigen. It contains ingredients backed by science and customers aren’t talking about harmful side effects. Click above to read about the sample offer.

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

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

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.

nursing infants….good or bad?

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.

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.

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.

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!

whats the name of this cheaper drink?

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

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.

How much sodiun is in a slim fast drink

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.

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

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

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.