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Was Slim-Fast the Original Liquid Diet Grift?

In the 1990s, Slim-Fast was so ubiquitous you certainly couldn't turn on the TV without hearing the line, ‘Give us a week, we’ll take off the weight’

By the time my brain was old enough to process what was being advertised by the “grown-up commercials” on television, Slim-Fast was already there. Even with my rudimentary, elementary-school-level understanding of body types simplified into three main categories — small, medium and large — Slim-Fast’s advertisements weren’t difficult to understand: They helped people move from the large category into one of the other two categories. There was simply no other way to interpret the Slim-Fast pledge (“Give us a week, we’ll take off the weight”); the belt cinched tightly around the Slim-Fast container; or the commercial’s slide-whistle sound effect.

What I was too young to realize at the time was that Slim-Fast had arrived on the market with a vastly different product offering rooted in misguided dietary science, only to have the rug quickly yanked out from under it. And that it would take a national media assault against a rival brand in order for it to ascend to the throne of nutrient supplementation.

How did Slim-Fast get its start?

When Slim-Fast first came to market in 1977, it represented the Thompson Medical Company’s attempt to land atop the wave of popularity being ridden by the liquid diet craze of the era. The key components of the liquid diet had been popularized by osteopath Robert Linn in his 1976 book The Last Chance Diet, in which Linn advocated for supervised fasting as a valuable tool to help overweight individuals lose cumbersome pounds. 

Linn had dispensed with nearly 70 pounds of his own body weight while subsisting on a nutrition plan consisting of three daily servings of red, predigested liquid protein manufactured by the Peerpark Corporation of Hackensack, New Jersey.

Unfortunately for Thompson Medical and nearly a dozen other players in this precariously positioned industry, the liquid diet’s popularity had already crested and was about to violently crash. In September 1977, the Food and Drug Administration ordered a recall of all products containing Peerpark’s predigested protein due to bacterial contamination, affecting roughly one dozen brands, Slim-Fast among them. In the process, an FDA spokesman issued a statement effectively burying the credibility of the liquid protein diet, stating, “There’s just no evidence to support the theory advanced by the proponents of the high protein diet that this or any other fad diet results in successful long-term weight loss.”

Fortunately for Thompson Medical, they had a precautionary ace up their sleeve. They’d been shrewd enough to diversify their product line so that they had more to offer customers than merely a ruby red liquid protein. Alongside their ill-fated cherry protein, Thompson had already begun to distribute a chocolate protein powder under the Slim-Fast name by the middle of 1977. In the months and years that followed, the Slim-Fast brand lived on in the form of its fallback option: the meal replacement shake. 

Is that when they got Tommy Lasorda as their spokesperson?

You’re getting nearly a full decade ahead of yourself.

The best thing that ever happened to the Slim-Fast brand wasn’t the once portly skipper of the 1988 World Series Champion L.A. Dodgers. Instead, it was the Cambridge Diet.

As the brainchild of Alan Howard of Cambridge University, the Cambridge Diet was promoted as a superior alternative to the liquid protein diet fad that preceded it. After “eight years of clinical study,” Howard and his team had reached the conclusion that consumers of their product would lose copious amounts of weight if they ingested nothing other than Cambridge Diet drinks three times daily, amassing a grand total of 330 calories in the process. Somehow, it was believed that whatever damage this austere nutrition plan would inflict on consumers’ bodies would be greatly attenuated by the inclusion of “all the body’s daily recommended needs of vitamins and minerals.”

The Cambridge Diet drinks sold incredibly well. In 1982, The Bellingham Herald reported that in Whatcom County, Washington, alone, it was estimated that 25 percent of shoppers were purchasing Cambridge Diet drinks. However, the same article addressed the controversy surrounding the Cambridge Diet’s plan of “scientific starvation,” and it included the warning from the FDA about the diet, which said, “There is clinical evidence that patients on severe caloric restriction may need twice as much protein and potassium as the Cambridge Diet supplies.”

Thompson Medical seized upon this opportunity and began advertising Slim-Fast in direct opposition to the Cambridge Diet in both newspaper ads and television commercials. They’d also learned a valuable lesson from the criticism and controversy that had led to the filing of a wrongful death lawsuit against the Cambridge Diet in 1982, and the company’s subsequent bankruptcy filing. 

Rather than advertising Slim-Fast as a product to be consumed in isolation from all other nutritive sources, Slim-Fast’s users would be advised to consume “a sensible dinner” as their third meal of the day, and also advised to mix the Slim-Fast formula with 1-percent or 2-percent milk if they felt the desire to consume more calories. 

What was the slickest element to all of this? On a per-serving basis, this early formulation of Slim-Fast actually delivered fewer calories to dieters than the Cambridge Diet, at 90 calories to 110, and only 5 grams of protein per serving. 

Not only did this render Slim-Fast to be even less nutritionally satisfying than the Cambridge Diet by at least one critical measurement, it also rained a deluge of doubt upon any purported benefits that Slim-Fast may have provided over and above what could have been similarly accomplished with a few minor dietary tweaks.

What do you mean by that?

Even when a serving of the improved, 1990s formulation of Ultra Slim-Fast was mixed with a cup of 2-percent milk, it tallied 240 calories and 14 grams of protein. Given the known nutritional value of a cup of 2-percent milk, it’s easy to deduce that the added Slim-Fast formula contained only 100 calories and roughly five grams of protein more than an ordinary cup of milk. 

If the value of the Slim-Fast formula was primarily owed to its protein and vitamin content, a Slim-Fast shopper would have received a greater quantity of complete protein with fewer calories simply by eating one large egg, which they could have washed down with a multivitamin and that same glass of milk, thereby exceeding all of Slim-Fast’s advertised benefits in the process. Come to think of it, they could have matched most of the advertised per-serving benefits of the Slim-Fast-infused milk just by drinking another half a cup of milk.

This is all to say nothing of the fact that in 1990, Slim-Fast was still declaring their nutrition plan to be sufficient relative to a recommended daily caloric intake of 1,055 calories. By comparison, daily caloric intakes of between 1,000 and 1,400 calories are the present guidance range established by the Department of Agriculture for developing nutrition plans for children between the ages of two and eight.

Wow! So it sounds like Slim-Fast was a scam from the get-go!

“Scam” is a harsh word. I’d prefer to say the Slim-Fast brand preyed on the lack of nutritional knowledge most consumers possessed during that era. Based on the fact that Consumer Reports revealed how sales of Slim-Fast dipped precipitously between 1991 and 1992 — down almost half — while one-fifth of the brand’s customers claimed to have gained at least five pounds while drinking it, I have to assume many people believed they were guzzling down a liquid fat burner and meal obliterator as opposed to a reputed meal replacement. 

Please keep this in mind: If any part of a company’s weight-loss pitch asks you to consume small quantities of their product and next to nothing else, your weight loss can’t be explained by the addition of anything that company is making; it’s being driven by the absence of everything else.