The chemical-packed, sugary meal replacer has somehow been around for 40 years

By Jeremy Glass
Updated March 22, 2018
Credit: Photo by DonNichols via Getty Images

If you’re old enough, you may still remember the original TV commercials that aired in the ‘80s and ‘90s. "A shake for breakfast, a shake for lunch, then a sensible dinner.”

“Give us a week! We’ll take off the weight!”

It all seems too good to be true: a diet where you can chug milkshakes instead of eating fruits and vegetables and actually lose weight. It’s not too good to be true. It's SlimFast. Also, yes, it’s definitely too good to be true.

Launched in 1977 by Thompson Medical Company, SlimFast was marketed as an alternative to the trendy weight-loss solutions at the time: grapefruits, Weight Watchers, and The Scarsdale Diet. The shakes were presented as a palpable and delicious solution to their weight problems. But what is the reality of this promise? Do these delicious smoothies live up to their expectations?

“SlimFast is terrible for you,” says certified nutritionist and a nutritional chef Melissa Eboli. “You'd be better off taking a scoop of sugar and adding it to water than drinking all of the chemical non-food, sugar-laden ingredients that make up SlimFast.”

Here’s how the meal-replacement shake is supposed to work: “Replace any two meals with SlimFast shakes, bars or cookies, enjoy one sensible meal of your choice and three 100-calorie snacks in between,” the company site says. While consumers shouldn’t be afraid to skip Sunday brunch, they should try to abstain from drinking sugar-sweetened beverages like juice and sodas. Along with this diet, the recommendations extend to drinking plenty of water and exercising regularly.

However, nutritionists have never backed SlimFast because of the myriad drawbacks that plague those who try the shake.

“Those shakes often contain less than 200 calories,” says Dr. Rachele Pojednic, a Boston-based Assistant Professor of Nutrition at Simmons College and former research fellow at Harvard Medical School’s Institute of Lifestyle Medicine. “This is often significantly lower than what most people are eating at a meal. The biggest problem with these kind of meal replacement diets is that they don’t tend to teach behaviors that people can stick to and rely on in the real world. Once they stop drinking the shakes, people tend to go back to eating meals that are significantly higher in calories, and they put the weight back on.”

Dr. Pojednic also says that fad diets such as these often don’t work because they aren’t sustainable.

“I believe that you should never do something with your diet that you’re not willing to stick to for the rest of your life,” Dr. Pojednic says. “You can cut calories in a similar fashion with nutrient dense foods like fruits and vegetables, and this way you are learning how to portion out real food rather than relying on expensive shakes that don’t really support healthy, long term behavior change.”

While we’d like to believe the magical solution to weight loss lies in a drink, the reality is much more complex. So what can be done to lose weight and maintain that weight loss? Diet and exercise. It’s the answer all those shake-sippers were afraid of hearing in the first place.

“Eat organic whenever possible,” Eboli says. “Stay away from processed foods, fried foods, and unhealthy food over all. Be conscious of caloric intake as well and don’t drink SlimFast. For starters, it is made from non-organic whey protein, which is inflammatory and turns into sugar once metabolized. The remainder ingredients are sugar, chemicals, and preservatives, which can definitely can contribute to weight gain.”

The reason SlimFast is often lumped into the “fad diet” category is because it is simply that: A fad diet that has somehow been around for 40 years. These kinds of weight-loss products, meal-replacement smoothies, and little cheats will always be around in some form. Just remember, if it seems too good to be true, it almost certainly is exactly that.