what are the side effects of drinking slim fast

The Slimfast diet plan is a combination of shakes and bars, which are available at grocery and drug stores. The diet and its products have evolved over the years to provide more variety in weight loss to people.

Many have had success with short-term weight loss using Slimfast (or another shake diet like Herbalife), an easy-to-use low-calorie plan. However, Slim-fit is not recommended as a long-term diet.

According to the Experts

“Diets that promote eating bars and shakes instead of real foods aren’t sustainable and often aren’t healthy. You might lose weight, but replacing your meals with highly processed meal replacements won’t deliver long-lasting, satiating results.”

—Kelly Plowe, MS, RD

What is Slim Fast?

what are the side effects of drinking slim fast
Slimfast in 1980s

Slimfast Diet was introduced as a diet shake line in 1977. Early shakes came in chocolate, vanilla, and strawberries. Its diet plan has a variety of shakes for breakfast and lunch with a sensible dinner.

During the 1990s, SlimFast expanded its line to include meal replacement bars. As low-carb diets came into fashion in the mid-2000s, the company launched low-carb and low-sugar options along with slim carb. In 2009, Slimfast again updated its schedule to a 3-2-1 plan that included three snacks, two meal replacements (shake or bar), and one dinner.

How does Slimfast works?

At present, the diet plan of Slimfast says to eat six times a day. Here is an example of how it works.

  • A complete meal of your choice (500 calories for women, 800 calories for men)
  • Two shakes or smoothies
  • Three 100-Calorie Snacks 4

You can buy Slimfast snacks or make your kind of snacks at home. The plan allows you to eat outside or cook at home for your main meal. You can enjoy alcohol in moderation, but it is recommended to limit alcohol consumption.

According to Slimfast, women on the diet consume about 1,200 calories per day in the plan and men consume 1,600 calories per day. This allows weight loss at a safe rate of about 1 to 2 pounds per week.

What’s on the food list?

The main center of the Slimfast diet is its shakes, which come in a variety of formulas and flavors. The new Advanced Nutrition Shakes and Smoothies provide more protein and less carbohydrate than the original shake. Here’s a look at the nutritional makeup of different SlimFast shakes:

  • Original Slimfast Chocolate Royale Shake Mix – contains 190 calories, 4 grams fat, 1 gm saturated fat, 30 grams carbohydrates, 4 grams fiber, 22 grams sugar, 10 grams protein. The primary (first) ingredient in the original SlimFast Chocolate Royale Shake Mix is ​​sugar followed by sunflower oil, cocoa, and other ingredients. Other flavors of the original Slimfast shake mix have a similar, but not identical, nutritional profile.
  • The original Slimfast Rich Chocolate Royale Shake (pre-made) contains 180 calories, 5 grams fat, 1 gm saturated fat, 24 grams carbohydrates, 5 grams fiber, 19 grams sugar, 10 grams protein. The primary ingredient in the original Slimfast Chocolate Royale is fat-free milk, followed by water, sugar, oil, and other ingredients. Other flavors of the original Slimfast shake are similar in nutrition.
  • Advanced Nutrition Slimfast Creamed Chocolate Smoothie Mix is ​​mixed with 8 ounces of skim milk and it has 190 calories, 3 grams fat, 0.5 grams saturated fat, 19 grams carbohydrates, 5 grams fiber, 13 grams sugar, 20 grams protein. Ingredients include whey protein isolate, soy protein isolate, cocoa, sunflower oil, thickeners, and sweeteners.

If you compare the ingredients and nutrition for these products to a specific smoothie that you make at home from scratch with fresh fruits, fiber-rich seeds, and other healthy ingredients, you are likely to be disappointed. It would be unusual to find oil or artificial sweeteners in most traditional smoothie dishes.

But many people who buy Slimfast enjoy the convenience of the products. Making a nutritious smoothie away from home is usually not an option.

Complex foodsNon-compliant foods
1. Slimfast shake, snacks and food bar

2. One “sensible” meal a day

3. Alcohol

4. Coffee
No foods are explicitly banned on the Slimfast diet, but calories are restricted.


On the Slimfast plan, you will eat six times a day. Replace any two meals with a Slimfast shake, have a portion-controlled meal a day, and enjoy three 100-calorie snacks in between.

Diet centers around Slimfast products, which are formulated so that people can successfully lose weight on the program. Shake lines of Slimfast come with low sugar and high protein varieties.

Slimfast’s advanced nutrition program has a 100-calorie snack pack program. There is a wide variety of foods to choose from so that you find something to satisfy your sweet or salty cravings. For example, you can buy salted sour cream and onion baked chips when you want something salty and cinnamon bun curly crisps when you need to satisfy your sweet tooth.

The nutritional facts for each snack vary, but each flavor provides both protein and fiber. When you fill foods with fiber and protein, you need to be satisfied after eating (and consequently eat less).

What are the side effects of drinking slim fast?

If you are considering a slim fast diet program, be aware of the possible side effects to decide if this is the program for you. There are some unpleasant side effects of drinking slim fast shake and eating meal replacement bandages, but many find that they are not troublesome enough to skip the use of the products altogether. Side effects can range from headaches to bloating, and some even feel tired during this plan. Let’s get to know what are the side effects of drinking slim fast?

Short term side effects of slim fast diet

Slim-Fast Shake and Nutrition Bar aim to replace two daily meals with a low-calorie option. Unfortunately, many dieters rely on meal-replacement products alone, resulting in very limited calorie intake, rapid weight loss, nutritional deficiencies, and health complications. Most of the side effects are temporary and will end as the body adjusts to the diet.

Transient side effects of drinking Slim Fast include the following:

  • Headache
  • Constipation
  • Intense hunger
  • Loose Stool
  • Discomfort
  • Gas and bloated

These side effects usually disappear with continued use of shake and bar, but may persist in some people. Dieters who are lactose intolerant may experience significant bloating and gas when using a milk-based slim fast shake.

Potentially Serious Side Effects of Slim fast

Serious side effects are usually the result of rapid weight loss and rarely occur with proper use of the product. Some dieticians report hair loss, gallstones, low blood pressure, abnormal blood sugar levels, abnormal QT intervals, ECG abnormalities, and cessation of menstruation.

Using shakes and nutrition bars as directed will usually not reduce your total daily calorie intake to dangerous levels. However, if your dinner is inadequate in calories or nutritional intake, you may experience the potentially dangerous side effects of Slim-Fast.

Health complications

Doctors often recommend a low calorie and very low-calorie diet to obese patients at risk of weight-related health complications, such as diabetes, high cholesterol, and high blood pressure. These diets are very beneficial when used as directed and under medical supervision. However, the National Institute of Diabetes and Digestive and Kidney Diseases warns that these diets can be dangerous when used by light or moderately overweight dieters.

Gall bladder disease

Gallbladder disease is the most common serious side effect associated with rapid weight loss. According to the University of Maryland Medical Center, rapid weight loss increases cholesterol production by the liver, resulting in super-saturation and increased risk of gallstones. Losing more than 3 pounds per week to the functioning of the gallbladder reduces the ability to contract and expel bile. This risk is as high as 12 percent after 8 to 16 weeks on a restricted-calorie diet.


Changing food with slim fast shakes can cause fatigue or weakness. This is because the body will have fewer calories available for use.

stomach problems

Slim fast can upset the stomach of some people. This may be due to dietary changes or artificial sweeteners used in some types of slim fast.

Weight gain and ups and downs

Slim-Fast only helps in weight loss if the user eliminates more common food calories from their diet than shakes. If the shake is consumed in addition to the normal diet, they can contribute to weight gain.

The use of products as directed may promote weight loss, but as long as low-calorie levels are not maintained, weight can easily return.


Slim fast may cause hunger feelings as the body may demand more calorie intake. The body often reduces calorie intake over time

Muscle loss

While very-low-calorie diets cause considerable loss of fat, they also cause dangerous muscle loss. Also, it is very difficult to lose weight once eating habits are normal. Unless you commit to eating healthy, engage in regular exercise, and change your lifestyle, you will regain the pounds you shed during your diet.

Seek medical advice

If you are using Slim-Fast products and experience any serious side effects, you should consult your doctor before continuing to use these products. To ensure that your weight loss efforts are successful, consult your doctor and follow the program guidelines carefully before starting any new diet program.

Minimum risk of side effects

Short-term use of meal-replacement products can help jump-start a weight loss program and provide a convenient way to shed a few pounds. When used as directed, Slim-Fast offers many health benefits with minimal risk of side effects.

Does Slim Fast Work?

Slim-Fast is a popular weight loss program that acts as a meal replacement system. The efficacy of such a program is difficult to measure because the results can be highly individualized and depend on many factors. In theory, diets that restrict calories and provide adequate nutrition should result in weight loss. The National Institutes of Health (NIH) has been reporting for years about the results of low-calorie diets and weight loss. By using different meal strategies, Slim-Fast consumers should be able to lose a certain amount of weight over time. However, how dramatic or rapid the results will vary from one person to another.

Advantage and disadvantage

Slimfast is just like other meal plans and it also has pros and cons which are given below: 

1. Easily available

2. Less expensive than Other commercial schemes

3. Easy to follow

4. Part controlled
1. Heavily processed food

2. Does not teach healthy eating skills, such as portion control, calorie counting, or low-calorie cooking

3. No face to face support

4. The taste

The pros

  • Provides easy access: You will find products in almost every supermarket, grocery store, and pharmacy across the country. You can also find products online.
  • Cost Less: Some diet plans, such as Jenny Craig, Nutrisystem, and Weight Watchers have to commit to a long-term program to get the lowest price. Slimfast does not require any commitment. You can try it for a day or a week or a month without canceling the membership meal service or plan.
  • Provides easy-to-follow instructions: No foods are off-limits and portion control is created when purchasing packaged snack products. Also, one meal per day that gives you pleasure allows you to consume more calories than some other diets that recommend a 300 or 400 calorie meal.
  • Built-in provides calorie counting: no need to download an app, log a magazine or food item. Almost all math is done for you, except for just one daily meal.
  • Exercise encourages: However, no formal program is provided. Some scientific studies have demonstrated successful weight loss with 5K meal replacement programs such as Slimfast, although many studies included guided support or education programs as part of the trial.


  • Processed foods are included: The program is primarily built on processed foods. Most health experts recommend that you reduce the amount of processed food that you consume and increase the intake of fresh or frozen fruits and vegetables, lean meats, seafood, and whole grains for optimal health.
  • Limits healthy cooking: You cannot learn how to cook healthy on a Slimfast diet plan. Cooking is not required in the program. And since you can consume hearty 500 to 800 calories in your staple food, you can easily eat outside or buy more processed food.
  • Clutter portion control: If you reach your goal weight on a Slimfast diet, you will eventually have to distance yourself from the program and lose weight. Because diet products are already controlled, you cannot develop the skills necessary to make it through this important transition without gaining weight.
  • Provides no maintenance plan: Once you reach your goal weight, you are advised to gradually reduce your use of Slimfast and increase your intake of specific foods. But beyond this, there is no structured plan that allows you to discontinue products altogether. If you have a habit of eating junk food on the diet, then you can be tempted to eat these foods after the diet is complete and lose weight.
  • Provides no personal support: However, the program offers a Facebook page and recipes on the website. Many large diet forums (such as Sparkpiece) have dedicated groups following Slimfast.
  • Reduces quality taste: The taste of Slimfast shake has been criticized online, but it is important to keep reviews in perspective. Consumers are often more motivated to post reviews online if the product is not liked. But to stay on the safe side, you may want to invest in just a few products until you are sure that you enjoy yourself enough to stay on the diet long enough to reach your goal.

How does it compare

The SlimFast Diet Plan has a 30-year track record of helping people lose weight successfully in the short-term. Many people who have used SlimFast do so to reach a quick, short-term goal, such as wanting to slim down for an upcoming event.

However, it is not a long-term weight loss solution or a healthy diet plan. The diet does not teach skills like healthy meal planning and preparation, essential for sustained weight loss

“In 2019 US News adn World Report best Diet gives the Slimfast 27 rank in the best diet and gives score 2.9/5.”

Its ranking is based on its high scores for shand-term weight loss and diabetes prevention and management, and high scores for nutrition, heart-health, and long-term sustained weight loss.

USDA Recommendations

The US Department of Agriculture (USDA) Dietary Guidelines provide recommendations for a healthy, balanced diet. The following nutrient-dense foods are considered part of a healthy diet:

  • Beans and legumes (all beans, lentils, peas)
  • Dairy (low-fat milk, cottage cheese, yogurt)
  • Fruits (apples, berries, watermelons)
  • Grains (quinoa, brown rice, oats)
  • Lean meat (chicken breast, fish, turkey breast)
  • Nuts and seeds (walnuts, almonds, sunflower seeds)
  • Oil (olive oil, avocado oil)
  • Vegetables and dark, leafy greens (bananas, spinach, broccoli, Swiss chard, green beans) 

Slimfast is a meal replacement diet but It’s hard for the Slimfast to meet the USDA’s definition of a healthy meal plan. The USDA recommends consuming approximately 1,500 calories per day for weight loss, but this number varies based on age, sex, weight, and activity level. Use this calculator to determine the correct number of calories for you.

Similar diet

Here’s how the SlimFast diet compares to similar meal-replacement schemes like Jenny Craig and Nutritionist.


Accessibility: Products can be purchased at your local grocery or drugstore.

Cost: An 11-ounce container of SlimFast protein powder makes 12 servings and retails for about $ 10.

Type of meal: Slimfast diet replaces two meals with Slimfast shake, bar, or cookies, three 100-calorie snacks in between meals and one regular meal a day.

Jenny Craig

Accessibility: Meals must be ordered online or taken from the Jenny Craig Diet Center

Cost: Meal plans range from $ 15 to $ 23 per day, plus shipping. A month’s meal can cost between $ 550 to $ 800.

Type of food: All food entrees are all frozen and need to be heated. Many people on the plan say that it is one of the most tasting summer and ready-to-eat food services on the market.


  • Accessibility: Products are ordered online or by phone. Wal-Mart also carries some nutritional products.
  • Cost: One-time delivery of a four-week meal plan for between $ 455 and about $ 680, depending on the plan selected.
  • Types of food: Three meals and two snacks each day include real food such as waffles with fried eggs and coffee, low-fat string cheese with carrot sticks, and grilled chicken sandwiches with a side salad.