Dr. Andrea Middleton - Is It Bad For You? Approved by Dr. Andrea Middleton

Is SlimFast Bad For You?

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Short answer

SlimFast is not good for you. It’s a processed meal replacement shake designed to provide nutrition alongside a reduced calorie diet. Though it’s generally effective for weight loss, reducing your daily intake to 1,200 calories might not be safe for everyone—there are more nutritious ways to lose weight.

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Long answer

SlimFast has been around for quite some time. The diet shake was formulated in 1977 and gained popularity in the early 1980s. As the name suggests, SlimFast was touted as a quick, easy way to lose weight. The original product line included flavored shakes intended to replace two daily meals: breakfast and lunch. For dinner, consumers were simply encouraged to “eat sensibly” and try to keep the calories under 500.

Believe it or not, this simple plan can actually work well for weight loss. SlimFast offers a structured program, which provides clear guidelines for people who struggle with counting calories. And it’s generally effective: studies have consistently shown that portion-controlled meals or meal replacements (like SlimFast shakes) help people lose more weight.

But is SlimFast safe? It’s not terrible for you... but there are definitely healthier alternatives.

First, let’s consider the product. SlimFast shakes are incredibly processed: the original formulation includes five grams of fiber and 10 grams of protein at only 181 calories per shake, which isn’t so bad. However, SlimFast also includes a whopping 18 grams of sugar and “milk protein concentrate.” Some variations also include sugar alcohols, which can cause stomach cramps and digestive problems. In moderation, this might not seem terrible... but SlimFast requires that dieters consume two shakes a day.

Here’s why it’s risky to rely entirely on one company to provide the majority of your daily nutrition: in 2009, ABC News reported that SlimFast recalled all shakes due to a possible bacteria contamination which posed a threat of serious illness.

And when it comes to the SlimFast program itself, eating a mere 1,200 calories per day might not be safe for everyone. For men ages 21 to 40, that’s only about half of the national recommended guidelines. The plan also falls short of daily nutritional guidelines for women in that same age group.

Consuming too few calories per day does serious damage to your body. Initially, you become fatigued easier and it’s harder to concentrate. But as your body enters starvation mode, it begins to feed on lean muscle tissue and your vital organs undergo serious strain. And starvation is not only dangerous—it’s unsustainable. Your body needs nutrients, and cravings become overpowering. This can lead to binge eating and, ironically, weight gain.

There’s no miracle drug—or shake, in this case—that will help you slim down instantly. Rather, the key ingredient to a successful weight loss plan is balance.