You might've seen SlimFast shakes at stores in the refrigerated section and assumed they were just a tasty shake, but there's an entire diet system built around the supplements. There are benefits and drawbacks to a program that relies on meal replacements, rather than actual meals.
On one hand, you might not be able to maintain your progress without the supplement. On the other hand it might be the amount of structure you need to successfully lose weight. Before you make up your mind, it's worth learning more about the system itself and some of the research behind it.
The SlimFast Diet
Typically, a diet is based around eating quality foods in specific quantities. The SlimFast diet plan is based more around supplements than whole food. To do the diet, you'll replace two meals per day with either a SlimFast shake, bar or cookie, according to the SlimFast website. You can choose any two meals to replace.
Your third meal of the day is a 500-calorie meal of real food. You're also allotted three 100-calorie snacks per day between meals, which are made by SlimFast. They also recommend drinking plenty of water through out the day and exercising at least 30 minutes.
One of the goals of the diet is to keep your meals as flexible as possible. Since you can choose which meals you replace with shakes or bars, you can plan ahead if you're going out to eat or have a special holiday meal.
The website also doesn't specify what you should eat for your 500 calorie meal, although they recommend avoiding sugary beverages like juice and sodas. If you decide to sign up for the diet, there's a meal plan, shopping list and recipes included.
For men, the recommended calorie intake is higher, according to the SlimFast website. They ask that men add 200 calories to each SlimFast meal, which can be an extra scoop of the meal replacement powder or an extra bar.
Read more: Good Post-Workout Shakes to Lose Weight
Various SlimFast Shakes
There's a host of different SlimFast protein products available on their website. They have an entire line of keto-friendly products. The keto diet is a high-fat, low-carb and moderate-protein diet. According to the SlimFast site, one keto shake has:
- 4 to 5 grams of net carbs
- 8 grams of protein
- 15 grams of fat
- 190 calories
The shakes are also free from artificial sweeteners, flavors, colors and gluten.
There's a diabetic formula, designed for people with Type 2 diabetes. The basic SlimFast nutrition facts of this shake, according to the website are:
- 9 grams of fiber
- 10 grams of protein
- 180 calories
Advanced Energy shakes are a line of meal replacement shakes from SlimFast that have added caffeine for an energy boost. These have:
- 20 grams of protein
- 5 grams of fiber
- 1 gram of sugar
- 1 gram of net carbs
- 24 vitamins and minerals
- As much caffeine as a cup of coffee
The SlimFast Advanced Nutrition shakes have the same nutrition facts as the Advanced Energy without the added caffeine. Both the Advanced Nutrition and Advanced Energy shakes have more protein than the SlimFast Original, which has 10 grams of protein.
The benefit of a diet like SlimFast is that there's plenty of structure. If you thrive on structure or don't know very much about nutrition, this can be helpful. While there's a structure to the diet, there's also some wiggle room that makes it easier to maintain your social life with your one 500-calorie meal per day.
If you find that you get hungry on most diets, the 100-calorie snacks in-between meals should help. On any diet you have to be careful that you're not lacking nutrients. SlimFast seems to do a good job of including vitamins, minerals and fiber in its products. Assuming that you use your 500-calorie meal wisely, you should have most of your nutrient needs met.
Pros of SlimFast
An article from Vanderbilt University Psychology reviewed research on the SlimFast diet and concluded it was an effective way to lose weight and maintain weight loss. The SlimFast website even has a section with over 40 clinical studies that show how effective it is.
A 2006 study published in the BMJ compared four popular weight-loss diets, including the SlimFast diet and Weight Watchers, and concluded that they were all effective at reducing weight. There probably isn't anything magical about SlimFast; it's the general principles they use for weight loss that work.
Adding up all the elements of the SlimFast diet, you arrive at about 1,340 calories per day for women and 1,740 calories for men. According to an article from the Office of Disease Prevention and Health Promotion, the average adult female needs 1,600 to 2,400 calories per day depending on activity level, and the average male needs 2,000 to 3,000.
For the average adult, the SlimFast diet puts you in a calorie restriction, which should make you lose weight. Losing weight from calorie restriction and exercise can help reverse the effects of something called metabolic syndrome, according to a March 2017 study published in Medicine and Science in Sports and Exercise.
It helps reduce LDL cholesterol, which is the bad kind. It also reduces obesity and hypertension. The study above looked at subjects who lifted weight in addition to their calorie restriction, so as long as you lift weights as part of your 30 minutes of recommended exercise per day, you should see similar benefits.
Read more: What Are the Benefits of a Protein Shake?
Cons of SlimFast
While the shakes contain essential nutrients like vitamins, minerals and fiber, the diet itself is heavily reliant on supplements. One problem of using so many products is that you aren't learning how to cultivate proper eating habits.
Eating a proper diet takes effort, especially if you cook your meals at home. You need to know how to shop at a grocery store, how to cook the food and what foods to eat. Eating shakes helps temporarily, but you don't want to become reliant on products.
While the calorie restriction from the SlimFast diet helps you lose weight, it might not be as effective as focusing on exercise. A May 2016 study published in Obesity Reviews showed that while diet and exercise each helped subjects lose weight, the group that exercised reduced more visceral fat. That means exercise can help you lose body fat instead of overall weight, which is important if you simply want to lean out.
- Obesity Reviews: "A Systematic Review and Meta‐Analysis on the Effects of Exercise Training Versus Hypocaloric Diet: Distinct Effects on Body Weight and Visceral Adipose Tissue"
- Medicine and Science in Sports and Exercise: "Effect of Resistance Training and Caloric Restriction on the Metabolic Syndrome"
- Health.gov: "Dietary Guidelines for Americans, 2015-2020: Appendix 2. Estimated Calorie Needs per Day, by Age, Sex, and Physical Activity Level"
- The BMJ: "Randomised Controlled Trial of Four Commercial Weight Loss Programmes in the UK: Initial Findings From the Bbc 'Diet Trials'"
- Vanderbilt University: "Health Psychology Home Page"
- SlimFast: "Diabetic Weight Loss"
- SlimFast: "Keto Meal Shake Mix"
- SlimFast: "How Does the Slimfast® Plan Work?"