The 21 Day Smoothie Diet: Is it a Healthy Weight Loss Diet?

About the 21 Day Smoothie Diet

The 21 Day Smoothie Diet is a weight loss diet created by Drew Sgoutas, a Health Coach and self-proclaimed nutrition expert. He developed this diet plan to help his clients lose weight in a healthy way and keep the weight off long-term. Drew also claims that replacing meals with smoothies can teach your body to crave healthy foods instead of sugar. The focus of the diet is on consuming more healthy fruits and vegetables and taking a break from processed foods. Since the creator claims that this diet is healthy, he states that it is not a fad diet. However, the Centers for Disease Control and Prevention says that fad diets are any diet that promises fast weight loss results [1].

The 21 Day Smoothie Diet plan is available as an e-book. It includes smoothie recipes, meal and snack tips, and shopping lists. The general guidelines of the diet are to replace two meals each day with a smoothie while also being allowed to eat one regular meal and two snacks each day.

What You Eat on the 21 Day Smoothie Diet

To follow the 21 Day Smoothie Diet, you are instructed to replace two of your meals, usually breakfast and lunch, with smoothies each day. You can also eat one regular low-calorie meal and two low-calorie snacks each day. The smoothie recipe ingredients vary in each recipe, but each smoothie contains fruits and vegetables. Some recipes have a small amount of protein and healthy fat.

There is an option to begin the 21 day diet with a 3-day detox. For the 3-day detox, you replace three meals a day with smoothies and only eat two low-calorie snacks. You do not eat a regular meal.

Healthy Smoothie Recipe Examples

Here are some examples of healthy smoothie recipes that may be similar to those in the 21 Day Smoothie Diet plan [9].

Kale Smoothie

Ingredients

• 2 cups kale leaves
• 1 banana (chopped and frozen)
• 1 cup blueberries
• ½ low-fat milk (or milk substitute)

Directions

• Add all ingredients to your blender and blend until smooth.

Chocolate Peanut Butter Banana Smoothie

Ingredients

• 4 oz soy, almond, or non-fat milk
• 2 tbsp natural peanut butter
• 1 banana (chopped and frozen)
• 1 tbsp cocoa powder (unsweetened)
• 1 packet of Splenda
• 2/3 cups of ice

Directions

• Add all ingredients to your blender and blend until smooth enough to drink.

Blueberry Antioxidant Smoothie

Ingredients

• 1 cup blueberries
• 1/2 banana (chopped and frozen)
• 1 handful of spinach
• ½ cup plain yogurt (or non-dairy yogurt)
• ½ low-fat milk (or milk substitute)

Directions

• Add all ingredients to your blender and blend until smooth enough to drink.

Mango Papaya Smoothie

Ingredients

• 1 cup mango
• 1 cup papaya
• 1 handful of spinach
• ½ cup plain yogurt (or non-dairy yogurt)
• ½ low-fat milk (or milk substitute)
• 2 tbsp fresh lime juice
• ¼ tsp almond extract

Directions

• Add all ingredients to your blender and blend until smooth enough to drink.

Potential Benefits  

Weight Loss

There are claims that the 21 Day Smoothie Diet may help you lose weight quickly. The main reason that this diet may help you lose weight is because it is a low-calorie diet. When you eat a low-calorie diet, you have a caloric deficit. A caloric deficit of 500 to 1000 calories less than your needed daily caloric intake for weight maintenance is necessary to lose one to two pounds in a week [2]. You can use a calorie calculator to find out how many calories you need to eat to lose weight.

The 21 Day Smoothie Diet book says that you do not need to count calories when following the diet plan but claim that the diet is roughly 1,500 calories a day. Overall, it is not the smoothies themselves that help you lose weight. It is the caloric deficit in your energy consumption. 

Detox

There is an option to begin the diet with a 3-day detox plan, where you replace three meals every day with smoothies and eat two low-calorie snacks each day. Detox plans generally suggest that they can help remove toxins from your body and help you lose weight because they cleanse your digestive system and prepare it for nutrient absorption [3].

Typically, detox diets only allow you to drink smoothies with strict ingredient guidelines, and snacks would not be allowed. There is also a lack of studies showing that detox diets are safe and effective in what they claim [3]. While this diet claims that drinking smoothies can help you detox, the research is inconclusive. 

Reduced Sugar Cravings

Substituting fruit for sugar can reduce your sugar cravings because your body digests fruit slower than artificial sugars, leaving you more satisfied [7]. However, research suggests that eating whole fruit is more effective than drinking fruit drinks, such as smoothies [5]. 

It is also important to recognize if the smoothie recipes include added sugar alternatives, such as Splenda or honey, they may increase your sugar cravings [7]. 

Increased Nutrition Intake

According to USDA 2020-2025 Dietary Guidelines for Americans, 90% of Americans do not eat the recommended daily amount of vegetables, and 80% do not eat the recommended daily amount of fruit [6]. The USDA recommends that adults eat 2 ½ cups of vegetables and 2 cups of fruit each day (based on a 2,000 calorie/day diet) [6].

If you do not meet these daily recommendations, drinking smoothies can be an easy way to add more fruits and vegetables to your diet.

Increased Fiber

The USDA recommends that adults consume 14 grams of fiber per 1,000 calories of their recommended daily caloric intake [6]. It may be hard to consume enough fiber if you do not eat enough fruits, vegetables, and whole grains [6]. Drinking smoothies packed with fruits and vegetables can help you meet the guidelines for fiber consumption [4]. Consuming the recommended amount of fiber can reduce your risk for coronary heart disease and chronic illnesses [4,6]. Consuming more fiber can also improve your digestion [4].

Other Benefits

The 21 Day Smoothie Diet is an easy diet plan to follow. If you purchase the book, you are provided with the smoothie recipes and weekly shopping list. You also do not need to count calories when following the diet.

Another benefit is that it is not a liquid diet. You are allowed to eat one solid meal and snacks, making the diet more sustainable for the full 21 days than other diets.

Potential Risks

You May Drink Too Many Calories

If you do not follow smoothie recipes or count the calories of your smoothies, you could potentially drink too many calories, especially if you are adding ingredients without measuring. Healthy fats and proteins are calorie-dense, and adding them to your smoothies without measuring will increase the calories of your smoothie.

It is also easy to underestimate the number of calories in a liquid form since it appears as a smaller amount than the ingredients would be unblended. If your smoothies are too high in calories, you might not lose weight.

Increased Blood Sugar

Fruit is naturally high in sugar. Even though fruits contain natural sugars, they still have the potential to spike blood sugar levels [4]. Consuming too much fruit can be risky for people with type II diabetes [4]. Anybody who needs to monitor their blood sugar levels should not begin a smoothie diet without consulting their doctor first.

Some recipes also include added sugar substitutes, such as artificial sweeteners and honey, which can also raise blood sugar levels.

Lacking Nutrients

Even though smoothies are packed with fruits and vegetables, following the 21 Day Smoothie Diet may leave you lacking protein and fats since smoothies are not nutrient complete. Aside from drinking smoothies, you are allowed to eat one solid meal and two snacks. However, the meals and snacks may not provide enough protein and fats unless they are carefully selected to contain those nutrients.

According to USDA guidelines, adults need to consume 5 ½ ounces of protein each day and have a total lipid consumption of at least 10-35% of daily caloric intake (based on a 2,000 calorie/day diet) [6]. Since smoothies are low in protein and fat, you would need to eat enough protein and fats in the one daily meal and two snacks.

You may be Hungry

Liquids are not as filling as solid foods since liquids are digested faster than solids. Studies have shown that eating a fresh fruit salad is much more filling than drinking fruit smoothies, even if the calorie consumption is the same [5].

Low-calorie diets generally leave you hungry because you eat fewer calories than you need to maintain your weight. The USDA recommends that adult women consume between 2,000 and 2,400 calories per day and that adult men consume between 2,400 and 2,800 calories per day to maintain body weight [6]. A caloric deficit higher than the recommended 500 to 1,000 calories per day for weight loss will cause hunger [2].

Other Risks

There is a lack of evidence the 21 Day Smoothie Diet is safe and effective, and it does not follow the USDA guidelines of a balanced diet [6]. Due to this, it is not a sustainable diet, and it is not safe to follow long term.

Frequently Asked Questions

Wrapping Up

While the 21 Day Smoothie Diet may appear harmless, there is a lack of scientific evidence to support the claims. Following the diet may help you lose weight, but this is due to the low-calorie consumption, not the smoothies themselves. There is also no proof that drinking smoothies can detox your digestive system or retrain your body to crave healthy foods. Following the diet may also cause nutrient deficiencies. In order for smoothies to replace a meal, they must contain enough protein, fats, and carbohydrates to support your body’s function.

The bottom line is that no diet is magic. Healthy weight loss is an ongoing lifestyle that consists of eating a healthy balanced diet, eating enough calories to sustain your body, and engaging in regular physical activity [8]. If you are looking into doing the 21 Day Smoothie Diet, discuss the diet with your doctor or a registered dietician before you begin, as it may put your health at risk.

References:

1. Centers for Disease Control and Prevention. (2021, September 13). Healthy Weight. https://www.cdc.gov/healthyweight/index.html
2. Harvard Health. (2020, July 11). Calorie counting made easy. https://www.health.harvard.edu/staying-healthy/calorie-counting-made-easy
3. (2019). “Detoxes” and “Cleanses”: What You Need To Know. https://www.nccih.nih.gov/health/detoxes-and-cleanses-what-you-need-to-know
4. (2020, October 16). Smoothies: Are They Good for You? https://www.webmd.com/diet/smoothies-good-for-you#1
5. Rogers, P. J., & Shahrokni, R. (2018). A Comparison of the Satiety Effects of a Fruit Smoothie, Its Fresh Fruit Equivalent and Other Drinks. Nutrients, 10(4), 431. https://doi.org/10.3390/nu10040431
6. Dietary Guidelines for Americans 2020-2025 (2020) https://www.dietaryguidelines.gov/sites/default/files/2021-03/Dietary_Guidelines_for_Americans-2020-2025.pdf
7. Harvard Health. (2013, July 1). How to break the sugar habit-and help your health in the process. https://www.health.harvard.edu/staying-healthy/how-to-break-the-sugar-habit-and-help-your-health-in-the-process
8. Centers for Disease Control and Prevention. (2022, January 24). Healthy Weight Loss. https://www.cdc.gov/healthyweight/losing_weight/index.html
9. DiGiacinto, J. (2021, August 13). 9 Healthy Smoothie Recipes (That Are Also Delicious). Healthline. https://www.healthline.com/health/healthy-smoothie-recipes

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