The SlimFast Shakes plan is a weight loss diet. It includes having two meal replacement drinks daily, one calorie-controlled meal, and three low-calorie snacks.
Today’s Slimfast Shakes is different than you might remember: Gone are the days of just rocking. The original plan promises you can lose weight with delicious snacks, meal replacements, and one sensible meal a day.
With the Slimfast Shakes plan, you eat two Slimfast Shakes meal replacements, three 100-calorie snacks (Slimfast snack bars, fruits, vegetables, and even nuts), and one 500-calorie meal provided. With this plan, you can eat up to 6 times a day.
The program says you can safely lose 1-2 pounds per week with this strategy.
They also offer products called Slimfast Advanced Nutrition, which provides high-protein, meal-replacement shakes or smoothies with less sugar than many other brands. They have more protein than the original Slimfast products. The Advanced plan also offers 100-calorie snacks and meal replacement bars.
This article examines the potential benefits and risks of the SlimFast Shakes plan. It also gives information about menu options and some alternative products.
Please note that the author of this article has not tried any of these products. All information presented is purely research-based and was correct at the time of publication.

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What is the SlimFast Shakes?
The SlimFast Shakes is a weight loss plan formulated by the company that focuses on meal replacement drinks and snack bars. Shakes come in regular, low-sugar, and high-protein varieties, and the snacks are 100 calories each. The company claims that weight loss results are possible within a week.
2021 U.S. News and World Report Best Diets rank the SlimFast shake diet as #26 in the Best Diets Overall, giving it an overall score of 2.8/5. Its ranking is based on the success rate for short-term weight loss but scores lower on nutritional content and mixed results for long-term weight loss.
Brand information
SlimFast was first launched in 1977 as a meal replacement shake.
The company eventually began offering snacks and products specifically for people with diabetes or on a ketogenic diet.
SlimFast states that it has “40+ years of proven weight loss success.” However, reviews are mixed depending on the source.
More positive reviews often say that the products are useful, tasty, and initially lead to weight loss. Less positive reviews reflect that sticking to the diet over the long term can be difficult, making it difficult to maintain weight loss.
How does it work
The SlimFast plan has a three-phase structure that includes meals, replacement shakes, and snacks.
A person can choose one of the following types of plans:
- Favorite Foods: This includes one meal a day and snacks based on preferences. There is no limit to the types of food a person can eat, as long as they stay within the recommended calorie range.
- Low Carb: This plan includes foods with below-average carb counts. A person can have a combination of homemade and packaged meals and snacks.
- Keto: This includes a variety of keto-friendly drinks, meals, and snacks.
- SlimFast Original: This is the company’s original diet plan and includes snacks, meals, and shakes.
Regardless of a person’s choice, their diet typically includes:
One 600-calorie meal
No foods are off-limits, as long as the meal falls within the total recommended number of calories. Depending on a person’s preference, this meal may be keto, low carb, or vegetarian, for example.
SlimFast states that males should add 200 calories to each meal replacement daily.
To help with meal planning, a person can find sample recipes on the SlimFast website.
Two replacement shakes
A person can buy their shakes as mixes or ready-to-drink products. Among the many flavors are strawberry, chocolate, vanilla, and cappuccino.
According to the company, each SlimFast shake contains 24 essential vitamins and minerals, along with 4–5 grams (g) of fiber and 10–20 g of protein, depending on the type a person chooses.
Three snacks between meals
SlimFast offers a range of sweet and savory snacks. Some are designed for ketogenic or diabetes-friendly diets. For example, the keto options include trail mixes, Cheddar Cheese Crisps, and bars.
Overall, anyone following a SlimFast plan should drink plenty of water and exercise for 30 minutes a day.
Once a person has reached their target weight, they can move to the SlimFast maintenance plan. This involves replacing one meal a day with a SlimFast shake or snack, eating two “sensible” meals of choice, and snacking between meals.
SlimFast Together
A person can download the SlimFast Together app for free on Google Play or the App Store.
The app offers:
- A quiz to help people find the best plan for them
- Tools to help plan and customize meals, including a calorie and macro calculator
- A recipe search function
- The option of purchasing SlimFast products in-app
- An automatically generated grocery list for pick-up or delivery
- Tools for tracking weight loss, water intake, and physical activity
How to get started with SlimFast
A person can sign up on SlimFast’s website or download the company’s Together app from GooglePlay or the App Store.
Signing up involves providing basic contact information, including an email address and a physical address. Next, a person answers questions designed to direct them toward the right plan for them. Regardless of the company’s recommendation, a person can choose the plan they like the best.
On the company’s website, as well as its app, a person can:
- Record their meals, exercise, and water intake
- Order SlimFast Shakes products
- Create meal plans
- View recipes
- Shop for ingredients from local stores
- Track their progress
Pros of the SlimFast Shakes Diet
Although healthcare professionals do not recommend the SlimFast plan, it does have a few practical advantages.
- Products available: SlimFast products are available in most supermarkets, grocery stores, and drugstores in the United States. They are also available online.
- Costs less than some other plans: Other diet plans like Jenny Craig, Nutrisystem, and Weight Watchers require you to commit to a long-term program to get a lower price. But SlimFast does not require a commitment. You can try a subscription food service or plan for a day or a month without having to cancel.
- Easy-to-follow instructions: No food is off limits for a reasonable meal, and the products are portion-controlled, making it easy to follow.
- Provides built-in calorie counting: No need to download an app, keep a diary or log food. Pretty much all the math is done for you—except for one daily meal, which you have to keep track of.
- Promotes exercise: SlimFast is an advocate of exercise, although no formal program is provided. Some studies have shown that exercise combined with meal replacement programs such as SlimFast can lead to weight loss.6 However, these studies often included guided support or education programs as part of the research.
- May cause weight loss: The SlimFast diet restricts daily calories and possibly leads to short-term weight loss. But research shows that meal replacement diets like SlimFast do little to support long-term weight management.
Cons of the SlimFast Shakes
The SlimFast Shakes program has some major drawbacks, especially if you follow it for a long time.
- Includes processed foods: The program is primarily based on processed foods. Most health professionals recommend reducing the number of processed foods you consume for optimal health and increasing your intake of fresh or frozen fruits and vegetables, lean meats, seafood, and whole grains. Studies continue to show a link between processed foods and chronic diseases, so long-term consumption of these products is not recommended.
- Limits to healthy cooking: You may not learn healthy cooking methods on the SlimFast diet plan and there is no need for cooking on the program. And since you can consume a hearty 500 to 800 calories in your main meal, it can be tempting to simply eat out or buy ready-to-eat processed foods.
- Ignores portion control: If you reach your target weight on the SlimFast diet, you will eventually need to disconnect yourself from the program and maintain your weight loss. Because diet products are already portion-controlled, you may not have the skills you need to make this transition without gaining weight.
- No long-term maintenance plan: Once you reach your target weight, it is recommended to gradually reduce your SlimFast consumption and increase your regular food intake. But beyond that, there is no structured plan to help get you off the diet.
- No personalized support: While it doesn’t have personalized nutritional guidance, the program does have a Facebook page and offers recipes on its website. These resources may not be enough for some people.
- Doesn’t taste good: Not everyone likes the taste of SlimFast. Those wishing to try this diet may benefit from tasting a few different products before purchasing anything in bulk.
- High in added sugar: SlimFast shakes are high in sugar, including added sugar. If you ate too many sweets before the diet, you may want to switch back to these foods. Studies show that consuming foods high in sugar and saturated fat can increase your risk of heart disease.
Is the SlimFast Diet a Healthy Choice for You?
Rapid weight loss is likely on the SlimFast diet, and its proponents claim you can stay on the program as long as you want. However, nutritionists do not recommend SlimFast as a long-term nutrition plan.
As with most calorie-restricted meal replacement diets, no matter how long you stay on calories, you’re likely to gain weight once you return to a normal eating pattern. Staying on the diet for a long time excludes many healthy foods and important nutrients from most meals.
The U.S. Department of Agriculture’s 2020–2025 Dietary Guidelines for Americans recommends consuming a variety of nutrient-dense foods and beverages for a balanced diet. These include:
- Vegetables and dark green leafy vegetables (cabbage, spinach, broccoli, chard, green beans)
- Beans and legumes (whole beans, lentils, peas)
- Dairy products (reduced-fat milk, cheese, yogurt)
- Fruits (apple, strawberry, melon)
- Grains (quinoa, brown rice, oats)
- Lean meats (chicken breast, fish, turkey breast)
- Nuts and seeds (walnuts, almonds, sunflower seeds)
- Fats (olive oil, avocado oil)
The USDA also recommends limiting foods and beverages that contain higher amounts of added sugar, saturated fat, and sodium. While the SlimFast Diet does not restrict any foods, it restricts all recommended foods for two out of three meals each day. Additionally, some SlimFast snacks can be high in sodium, and a few shakes contain added sugar.
While the SlimFast diet plan can help many people lose weight successfully in the short term, it is not a long-term weight loss solution or a sustainable eating plan. The diet does not teach important skills such as healthy meal planning and preparation necessary for sustained weight loss.
The typical recommendation for calorie intake is about 1,500 calories per day for weight loss, although this number varies with age, gender, weight, and activity level. The SlimFast Diet provides 1,200 calories per day for women and 1,600 calories per day for men; this may not be enough calories for some people. Use this calculator to determine the right amount of calories for you.
Studies on SlimFast
Research into the SlimFast plan indicates that it can promote weight loss. However, other weight loss programs may be just as effective.
A 2006 study that compared SlimFast with the Atkins diet, the Weight Watchers Pure Points program, and the “Eat Yourself Slim” plan found that all participants reported significant — and comparable — losses in weight and body fat over 6 months, compared with the control group. All the participants had overweight or obese at the beginning of the study.
A smaller study of 63 people with obesity found that following the SlimFast plan for 6 months led to an average 7% loss of body weight.
According to one review of six randomized controlled trials of SlimFast and similar meal-replacement programs, these plans can safely and effectively lead to significant, sustainable weight loss. However, several of the researchers involved were affiliated with SlimFast.
Some research indicates that SlimFast may help adolescents with obesity lose weight in the short term. However, the team found that this plan may not help adolescents maintain weight loss.
It is important to note that these studies typically involve participants with overweight or obesity. Therefore, it is difficult to know how effective the SlimFast plan might be for people with more moderate weights.
In addition, many of these studies are older and may not reflect current weight-loss strategies.
Summary
The SlimFast Shakes plan can lead to significant weight loss for some people, at least in the short term. However, maintaining results can be difficult.
Also, SlimFast Shakes products can be prohibitively expensive, especially in the long run.
Restricting calories and portion sizes and getting exercise and diet tips from health professionals and expert sources can be just as effective.
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