What Is the Smoothie Diet?

Smoothie diet

Verywell / Debbie Burkhoff 

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 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 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 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, many 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, you will 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.

There is also some guidance in the e-book for the one solid-food meal you will consume each day (recommendations for what to eat, and some "whole food" recipes), as well as suggestions for low-sugar, high-fiber snacks. To reiterate the above, 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

Some smoothie recipes (on this diet and elsewhere) can be very thick. It's tempting to thin them out with fruit juice, but juice can add a lot of calories and unnecessary sugar. Water will make your smoothie easier to drink and ice will add thickness. Try decreasing the amount of juice and adding water or ice to get the right thickness and flavor for you to keep the sugar levels down.

On the "detox" plan, all three daily meals are replaced with smoothies. On the 21-day plan, you'll consume two meal-replacement smoothies (breakfast and lunch), one solid-food meal, and a few snacks. If the idea of subsisting on nothing but smoothies seems unrealistic to you, plan for a "flex day," in which you consume one smoothie and two regular meals instead.

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 2 meals a day

The recipes in the 21-Day Smoothie Diet contain plenty of fruits and veggies, which are an essential part of a healthy diet. They tend to be low in calories and rich in phytonutrients. The smoothie recipes contain a lot of fruit. While fruit offers healthy nutrients, it also contains a lot of naturally-occurring sugar. Some smoothies also call for honey, which adds even more sugar.

Most of the diet's smoothies are also low in protein, and a few fall short in healthy fats. Sgoutas does emphasize getting enough protein throughout the day, recommending at least 50 grams daily by eating a little with each meal and snack. 

However, some people may need additional guidance on this issue—and without proper planning, could fall short of meeting their protein needs. If you are using a smoothie as a meal replacement, make sure it contains each essential macronutrient: protein, fat, and carbohydrates.

Pros and Cons

  • Emphasis on fruits and vegetables

  • Less calorie-counting and food tracking

  • Shopping lists included

  • Restrictive

  • High in sugar

  • Preparation could be time-consuming

  • Not sustainable

  • Lacks scientific support

A lot of this diet's rules and instructions are spelled out in the e-book, leaving less to figure out on your own. But 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 many other eating plans, however, a benefit of this particular smoothie diet is that it doesn't require carbohydrate counting, a food diary, or calorie counting. It does recommend being aware of the calorie count in the daily solid-food meal, however. Since recipes and weekly meal plans (smoothie plans, that is) are provided, there is not a lot of decision-making or tracking involved, which is a boon for some people who follow this diet and are short on time.

The e-book contains shopping lists broken down by smoothie and by week, which simplifies grocery-store visits during the three-week duration of the diet. But, even with these benefits, experts have concerns about the Smoothie Diet's effectiveness and sustainability.

Is the Smoothie Diet a Healthy Choice for You?

In general, fruit smoothies tend to contain plenty of calories from carbohydrates and perhaps a small amount of fat. But they also need a good source of lean protein. Protein helps build muscle, which you need to maintain a healthy metabolism. Try adding a tablespoon or two of chia seeds to a smoothie. The seeds will thicken your drink and provide a boost of fiber as well.

Smoothie diets like this one are popular, but you'll also find similarities between the 21-Day Smoothie Diet and other short-term, low-calorie, meal-replacement diets such as SlimFast. Be aware that these diets don't meet expert advice on healthy eating plans.

For weight loss, the U.S. Department of Agriculture (USDA) recommends a daily caloric intake of about 1,500 calories. Sgoutas does recommend approximately 1,500 calories per day in the e-book—but the smoothie recipes in The Smoothie Diet clock in at much less than that, making it difficult to reach the 1500-calorie target without overindulging in the one daily meal.

Creating a calorie deficit is often the best way to lose weight successfully and sustainably. But the right number of calories 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.

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 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

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.

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). Organs, like the kidneys, are meant to naturally detox the body. No one food or food combination can do this by itself.

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). This 175-calorie peanut butter smoothie is creamy and sweet without the addition of any extra sugars.

In addition, it is possible to lose muscle mass if you lose weight too quickly. If someone goes back to their regular eating habits and increases their calorie intake, they may find the pounds creeping back. 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 women, and other 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.

Use fresh or frozen fruit, such as blueberries, strawberries, mango, peaches, or apples. But also, branch out and use ingredients such as watermelon, spinach, or kale to get additional vitamins and minerals.​ Try this ​sweet green smoothie to get vitamin-packed green veggies with your morning meal.

If weight loss is your goal, avoid using high-fat ingredients to get a creamy texture. A smoothie made with ice cream, gelato, frozen yogurt, or a large amount of peanut butter is delicious, but it may be too high in calories, fat, and sugar to help you lose weight. Bananas, either frozen or at room temperature, provide a thick, smooth texture without the added fat and calories.

If you love the taste of peanut butter, opt for an all-natural brand and keep your portion about one tablespoon. If you are looking to reduce the calories you can consider powdered peanut butter keep in mind that it may not be as filling. Experiment to find smoothies that work for you, and other healthy recipes that provide lots of nutrition without a lot of 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, and 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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