The SlimFast Diet: Why It’s Bad for You and What’s Better

Imagine a diet where you can magically slurp on drinks that leave you feeling full, so that you can enjoy a healthy, well-balanced meal later in the day. You’ll sneak in a few snacks, lose weight quickly, feel great and you’ll never struggle with the scale again. Sounds nice, doesn’t it?

That’s the fantasy that diet food giant SlimFast is peddling. And I won’t mince words: it’s exactly that, a fantasy. While it might sound nice on paper (or on a slick website), the SlimFast diet is neither healthy nor a good long-term strategy to lose weight. Let’s dig into why.

What Is the SlimFast Diet?

SlimFast came about in the late 1970s, designed as a powder that was mixed with low-fat milk. The idea was to replace breakfast and lunch with these powdered meal replacement shakes and then enjoy a “sensible dinner” of 600 calories.

Nearly 40 years later, the basic premise is still the same. How SlimFast “works” is that you replace two meals a day with shakes or — in a true sign of the times — smoothies or bars. You “indulge” in three 100-calorie snacks throughout the day (made by SlimFast, of course) and then wrap up the day with a 500-calorie meal of your choice, hopefully made from real food.

As long as you’re enjoying this calorie-reduced diet (borderline starvation mode for some folks), exercising regularly, drinking plenty of fluids, aren’t nursing, pregnant, under 18 or following a doctor-prescribed diet, you’ll see results! (But individual results may vary, of course.)

There’s quite a few variety under the SlimFast umbrella these days. From the humble meal replacement shakes, an empire was born. Shakes come in a range of flavors, from “creamy chocolate” to “caramel latte.” There are meal replacement bars and smoothies, snacks like “s’mores drizzled crisps” and, terrifyingly, an “Eat Less Pill.”

If you’ve been a follower of my site for anytime — or even have just taken a quick browse — you can probably guess some of the reasons I detest SlimFast and similar products like Herbalife, Soylent and the lot. But I’ll get to that later. First, let’s unpack what exactly it is you’re drinking.

In theory, replacing a meal with a shake doesn’t seem so terrible. In fact, I often start my days with a homemade protein shake. But there’s nothing homemade about the SlimFast diet — it’s more science experiment.

Bad Ingredients

The ingredients in the SlimFast diet should give anyone pause. Let’s dissect the SlimFast Advanced Nutrition Creamy Chocolate Shake as an example.

It doesn’t start off so badly, as water is the first ingredient in this shake. Because ingredients are listed in the order of how frequently they appear (essentially how much of the ingredient is in the product), this means that water is the most active ingredient. So what else is it mixed with?

Canola oil. Is canola oil bad for you? You bet. Canola oil is chock-full of GMOs, since over 90 percent of it is made from GMO corn. The dangers of GMO foods range from an increase in antibiotic resistance, problems with the endocrine system, reproductive issues, increases in allergies — and that’s just what we know about.

Canola oil is also a partially hydrogenated oil, meaning it’s made from a triple processing technique requiring deodorization, high heat and the toxic solvent hexane. (1) It’s this process that causes a serious amount of trans fat to be produced, which raises bad cholesterol and lowers the good type.(2). I recommend olive oil, coconut oil or ghee instead.

But enough about canola oil! What else is in these shakes?

Maltodextrin. Maltodextrin is a highly processed white powder used to thicken foods or liquids — that shake has to feel hefty somehow! (3) It’s also used as a preservative to help processed foods last longer. Because it’s cheap to produce, you can find it in products ranging from salad dressing to body lotion.

Maltodextrin has a similar calorie count to table sugar, but its glycemic index is much higher. That means it’ll cause your blood sugar to spike quickly then crash. This isn’t just dangerous for anyone who has diabetes or doesn’t want their energy to plummet mid-day. One study found that maltodextrin can keep healthy gut bacteria from growing while increasing bacteria like E. coli, raising the risk of autoimmune diseases. (4)

Natural and artificial flavors. Why? I’d rather eat food and enjoy their actual flavors then inject artificial flavors into my drinks.

Carrageenan. SlimFast shakes are full of carrageenan. What is carrageenan? It’s an ingredient that’s extracted from edible seaweed and used to thicken and stabilize foods and drinks.

While the scientific community often debates on exactly what side effects carrageenan can have on people — it’s been linked to everything from fetal toxicity to liver cancer — one that’s fairly agreed upon is that carrageenan is super inflammatory. Because inflammation is at the root of most diseases, I say it’s not worth taking your chances, and it’s best to avoid carrageenan.

Other icky ingredients. And of course, there are more unfortunate ingredients in SlimFast. I counted six different types of sweeteners in the ingredients list — don’t let names like tapioca syrup and brown rice syrup fool you. There’s also more water, powdered milk, salt and a “vitamin and mineral blend.”

“But I’m desperate,” you say. I just want to lose those last five pounds. If you’re trying to do that on the SlimFast diet, good luck.

Why SlimFast Diet Is a Bad Idea

It’s unsustainable. For starters, diets like this one are not sustainable over the long run. While you might lose a few pounds while you’re on it, SlimFast does not set you up for success. It sets you up to become a slave to a billion dollar multinational corporation. (5)

Whatever issues you have with food, whether it’s emotionally eating, not knowing how to cook healthy meals or looking for a quick fix, it’ll still be there. Unless you’re committed to staying on SlimFast for the rest of your life, choosing this diet will not address the underlying problem. And I promise, real life will get in the way.

The ingredients are not good for you. Essentially, you could take a big glass of water, dump some sugar in it, add a crushed up multi-vitamin, add a few drops of milk, chuck in some cocoa powder and oil and have a drink very similar to SlimFast — and hey, it’d be cheaper!

It’s expensive. Speaking of prices, SlimFast doesn’t come cheap. At two shakes and three snacks a pop, you’re going to be shelling out quite a bit of money. You can certainly get more bang for your buck with fresh or frozen fruits and veggies.

Sugar can make you fat. Because SlimFast foods are so full of sugar, you might be running a hamster wheel when it comes to keeping the weight off. Sugar affects leptin, the “starvation hormone.” Leptin is secreted by fat cells. As our fat cells increase, they secrete leptin, which tells the brain that we’re full and don’t need more food.

But if you’re consuming so much sugar that your brain becomes resistant to leptin, it never receives the signal that you’re full. It’ll keep seeking out more food, hoping to finally get that “I’m full” memo from leptin. Oops.

You’re not eating enough calories. SlimFast shakes are about 180 calories a pop. If you drink two a day, add in the three 100-calorie snacks and the 500-calorie dinner, you’re consuming only 1,160 calories a day. This is far fewer calories than the USDA recommends men and women eat daily.

Remember, according to SlimFast, you should also be exercising regularly.  The average person isn’t going to have very much energy to exercise when they’re eating fewer than 1,200 calories a day. Actually, they probably won’t have too much energy in general.

Better Options

So I’ve finally convinced you to stay away from SlimFast and its products. But if you are struggling with your weight, what can you do?

For starters, I recommend trying my healing diet. I bet you’ll be surprised at how many foods you love are on there. I guarantee that if you phase out processed foods, sugary drinks and transition to whole foods, you will see a difference.

But maybe you’re someone who prefers following set rules and you’re looking for the best diet plans to lose weight. Whether you opt for the Mediterranean diet, choose Paleo or decide to try low-carb or keto, these diets all encourage enjoying real foods.

You can also try replacing a meal with a shake made from recognizable ingredients. My Superhuman Shake for Muscle and Strength is a great way to fuel up before a workout. This Berry Protein Smoothie tastes like dessert but is full of protein.

When you’re choosing your workout plan, incorporating bodyweight exercises alongside high-intensity interval training workouts, or HIIT, will help you see results quicker.

Final Thoughts

I know that trying to lose weight and get in shape can be difficult. But there is no quick fix, and products like SlimFast aren’t designed to help you reach your physical potential. They’re created to keep you buying them. After all, if gimmicks like SlimFast actually worked, they’d be out of business by now, since no one would have trouble losing weight.

Choosing the right foods and ingredients will make you feel so much better in the long run — and the way you look will reflect that, too.