At Verywell, we believe there is no one-size-fits-all approach to a healthy lifestyle. Successful eating plans need to be individualized and take the whole person into consideration. Prior to starting a new diet plan, consult with your healthcare provider or a registered dietitian, especially if you have an underlying health condition.
The 21-Day Smoothie Diet, created by health coach Drew Sgoutas, claims that replacing some of your meals with smoothies will lead to quick and easy weight loss. As with so many weight-loss plans, including restrictive diets like this one, the details are important.
As part of a balanced diet, smoothies can help you lose weight. But ingredients, portion size, and your overall eating plan will make all the difference. A diet consisting of mostly smoothies, however, may not work for everyone as a solution for long-term weight loss success.
Sgoutas (who is not a registered dietitian), created the 21-Day Smoothie Diet to help his clients lose weight. His e-book, "The Smoothie Diet," contains 36 smoothie recipes, shopping lists, and a three-week schedule that details which smoothies to prepare each day. The e-book also offers a "detox" plan with recipes and instructions for replacing three meals a day with smoothies for a total of three days.
The 21-Day Smoothie Diet advises eating normally (but still "healthy") one day per week and includes a recommended food list for that day. Sgoutas suggests repeating the 21-day cycle any time you would like to lose weight, but there is limited research to suggest that a smoothie diet is an effective method for weight loss.
In the short term, followers of this diet may lose weight. But to keep it off, they might have to stay on the diet past the 21-day period, which is not a healthy long-term solution since it means that important food groups containing vital nutrients are continuing to be restricted.
For most people, two homemade meal-replacement shakes per day, plus a "regular" meal, may not provide the right balance of calories, protein, carbohydrates, and healthy fats the body needs. Any meal-replacement diet is tough to stick with for the long haul since these replacements often aren't as satisfying as solid food.
What Experts Say
"The Smoothie Diet promises rapid weight loss, but pounds shed may be regained when transitioning back to normal eating habits. While increasing fruit and vegetable intake is smart, some people may struggle to meet protein requirements on this diet without proper planning."
—Chrissy Carroll, RD, MPH
What Can You Eat?
On the 21-Day Smoothie Diet, followers prepare and drink two smoothies a day as meal replacements. The smoothie ingredients vary, focusing on lots of fruits and vegetables with some protein and healthy fats.
The diet's e-book offers some guidance on the one solid-food meal followers are advised to consume each day (including recommendations for what to eat and some "whole food" recipes), as well as suggestions for low-sugar, high-fiber snacks. You are also allowed to eat normally one day per week, so long as the meals adhere to the recommendations in the e-book.
What You Need to Know
The strict "detox" plan replaces all three daily meals with smoothies for three days. On the 21-day plan, you'll consume two meal-replacement smoothies (breakfast and lunch), one solid-food meal, and a few snacks. Though not a part ofSgoutas’ "official" smoothie diet, some plan for a "flex day" to make the diet more sustainable.
However, Sgoutas points out that if the regular meals are too high in calories, the diet probably won't be effective for weight loss. Also of note: The e-book suggests that this diet is not for people with food allergies.
What to Eat
Lots of fruits and vegetables
Nutritious meal once per day
What Not to Eat
No solid food for two meals a day
The recipes included in the 21-Day Smoothie Diet contain plenty of fruits and veggies, tend to be low in calories, and provide important phytonutrients. While fruit offers healthy nutrients, it also contains naturally occurring sugar, which may not work for you if you're trying to reduce your sugar intake. Some smoothies also call for honey, which only adds more sugar.
Additionally, most of the diet's smoothies are very low in protein, and a few fall short in healthy fats. Sgoutas does emphasize getting enough protein throughout the day and recommends at least 50 grams daily by eating a little with each meal and snack. However, some people might find it difficult to meet their daily protein needs on this plan, especially those who don't spend a lot of time meal planning.
If you are using a smoothie as a meal replacement, make sure it contains each essential macronutrient: protein, fat, and carbohydrates. You might consider consulting with a nutritionist or registered dietician for more guidance—though they would likely suggest that you avoid a smoothie-based diet and try other, healthier strategies instead.
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Pros and Cons
Pros
Emphasis on fruits and vegetables
Less calorie-counting and food tracking
Shopping lists included
Cons
Restrictive
High in sugar
Preparation could be time-consuming
Not sustainable
Lacks scientific support
A lot of the Smoothie Diet's rules and instructions are spelled out in the included e-book. While it seems simple, preparing two or three smoothies a day (and cleaning the blender afterward) takes time. And while you can easily prep a morning smoothie for a quick breakfast on the go, it's more difficult to have a smoothie for lunch if you're away from home and don't have access to all your ingredients and a blender.
Unlike other eating plans, the Smoothie Diet doesn't require carbohydrate counting, a food diary, or calorie counting. It does, however, recommend being aware of the calorie count in the daily solid-food meal. Recipes and weekly meal plans (smoothie plans, that is) are also provided in the e-book, as are shopping lists broken down by smoothie and by week. Despite these conveniences, however, experts remain concerned about the Smoothie Diet's overall effectiveness and sustainability.
Is the Smoothie Diet a Healthy Choice for You?
In general, fruit smoothies tend to contain calories from carbohydrates and a small amount of fat. But to provide a well-rounded meal, they also need a good source of lean protein. Protein helps build muscle, which you need to maintain a healthy metabolism. A diet consisting of mostly smoothies would likely fall short of meeting your daily intake of protein.
Smoothie diets like the 21-Day Smoothie Diet are popular, but you'll also find similarities between this diet and other short-term, low-calorie, meal-replacement diets such as SlimFast. Be aware that these diets do not meet expert advice on healthy eating plans.
The USDA 2020–2025 Dietary Guidelines for Americans recommends consuming a variety of nutrient-dense foods and beverages while staying within the recommended limit of 2,000 calories a day for weight management.The 21-Day Smoothie Diet does not adhere to federal guidelines since it excludes many healthy foods that make up a balanced diet.
For weight loss, the USDA recommends a daily caloric intake of about 1,500 calories. While Sgoutas recommends approximately 1,500 calories per day in the e-book, the smoothie recipes in "The Smoothie Diet" clock in at much less than that, making it difficult to reach the 1,500-calorie target without overindulging in the one daily solid-food meal.
Creating a calorie deficit is often the best way to lose weight successfully and sustainably. But a healthy daily calorie goal is different for everyone, because of factors such as age, sex, weight, and activity level. Use this calculator to determine the calorie goal that might work for you.
USDA nutrition guidelines suggest filling your plate with a balanced mix of protein, fruit, vegetables, grains, and dairy. That's for each meal—not just one per day. It's difficult to get all those nutrients and food groups into a meal-replacement smoothie and still have it be tasty and low in calories at the same time.
Health Benefits
It is likely that people will lose weight quickly when they start the 21-Day Smoothie Diet because they are cutting calories (while also potentially cutting nutrients like protein and healthy fats). But replacing meals with liquids, and living on so few calories, isn't something that most people can safely continue to do for the long term.
Health Risks
There is no strong scientific evidence to support the notion of detox diets—in part because there is no clear definition of what a "detox diet" does. The body naturally "detoxes" itself through digestion and excretion (such as bowel movements and sweat). Detoxification is a primary function of organs like the liver and kidneys. No one food or food combination can do this on its own.
The high sugar from the Smoothie Diet could be an issue for people with certain medical conditions (which is why it's not recommended for people with diabetes). In addition, it is possible to lose muscle mass if you lose weight too quickly. And if someone following the weight-loss diet goes back to their regular eating habits and increases their calorie intake, they are unlikely to maintain their weight loss long-term. This could be why the e-book suggests repeating the 21-day diet as often as necessary.
Keep in mind that "detox" diets are not indicated for some people, including children, pregnant and nursing people, and people with certain health conditions. Before starting any diet be sure to discuss it with your healthcare provider first.
A Word From Verywell
While you can get recipe ideas from "The Smoothie Diet" e-book, consider making your own healthy smoothies and using them as one part of a sensible, balanced eating plan. For best results, measure each ingredient and tally the complete calorie count for your drink. This could save you from making a common weight loss mistake—underestimating the impact of liquid calories.
Remember, following a long-term or short-term diet may not be necessary for you and many diets out there simply don’t work, especially long-term. While we do not endorse fad diet trends or unsustainable weight loss methods, we present the facts so you can make an informed decision that works best for your nutritional needs, genetic blueprint, budget, and goals.
If your goal is weight loss, remember that losing weight isn’t necessarily the same as being your healthiest self, and there are many other ways to pursue health. Exercise, sleep, and other lifestyle factors also play a major role in your overall health. The best diet is always the one that is balanced and fits your lifestyle.
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