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, the details are important.

As part of a balanced diet, smoothies can help you lose weight. But ingredients, portion size, and 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.

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 detailing 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 three days.

The 21-Day Smoothie Diet advises eating normally (but still "healthy") one day per week and includes a recommended food list. Sgoutas suggests repeating the 21-day cycle any time you want to lose weight, but there is limited research 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 past the 21-day period, which is not a healthy long-term solution since it means that important food groups containing vital nutrients are restricted.

For most, 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 Can You Eat on the Smoothie Diet?

On the 21-Day Smoothie Diet, followers prepare and drink two smoothies as meal replacements daily. Smoothie ingredients vary, focusing on fruits and vegetables with protein and healthy fats.

The smoothie diet's e-book offers 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, as 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 of Sgoutas’ "official" smoothie diet, some plan for a "flex day" to make the plan more sustainable.

However, Sgoutas points out that if regular meals are too high in calories, the diet probably won't be effective for weight loss. Also of note: The e-book suggests this diet is not for people with food allergies.

The recipes included in the 21-Day Smoothie Diet contain plenty of fruits and veggies, which tend to be low in calories and packed with important phytonutrients. While fruit offers healthy nutrients, it also contains naturally occurring sugar, which may not work if you're trying to reduce sugar. Some smoothies also call for honey, which only adds more sugar.

Additionally, most of the diet's smoothies are low in protein and a few fall short in healthy fats. Sgoutas emphasizes getting enough protein throughout the day and recommends at least 50 grams daily by eating a little with each meal and snack. However, some might find it challenging to meet their daily protein needs on this plan, especially those who don't spend a lot of time meal planning.

If you use a smoothie as a meal replacement, ensure it contains each essential macronutrient: protein, fat, and carbohydrates. Consider consulting with a nutritionist or registered dietician for more guidance—though they would likely suggest you avoid a smoothie-based diet and try other, healthier strategies instead.

Pros and Cons of the Smoothie Diet

Most 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 daily (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 challenging 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 are also provided in the e-book, as are shopping lists broken down by smoothie and 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 contain calories from carbohydrates and a small amount of fat. But to provide a well-rounded meal, smoothies also need 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 protein goal. Incorporating a conventional or organic protein powder can help make up for some of this shortfall.

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. These diets do not meet expert advice on healthy eating plans.

The USDA 2020–2025 Dietary Guidelines for Americans recommends consuming nutrient-dense foods and beverages while staying within the recommended limit of 2,000 calories daily for weight management. The 21-Day Smoothie Diet does not adhere to federal guidelines since it excludes many healthy foods for 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, gender, weight, and activity level. Use this calculator to determine the calorie goal that might work for you.

Health Benefits

People will likely 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 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 because there is no clear definition of what a "detox diet" does. The body naturally detoxes 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. If someone following this weight-loss diet goes back to 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.

A Word From Verywell

While you can get recipe ideas from "The Smoothie Diet" e-book, consider making healthy smoothies and using them as 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- or short-term diet may not be necessary for you, and many diets out there 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.