Obesity has become a global public health concern, driving the need for evidence-based dietary strategies for weight loss and maintenance. Weight management depends on complex factors, including the amount and type of food consumed, as well as meal timing. This article provides a comprehensive review of several popular "system 21" style diets, examining their effectiveness, nutritional value, and potential drawbacks. These diets often promise rapid weight loss through a combination of calorie restriction, specific food choices, and exercise.
Understanding the Principles of Weight Management
An energy deficit is the most important factor in weight loss. Dietary management focuses on the concept of "eat less, move more." A low-calorie diet typically involves consuming 1,000-1,500 calories per day, with deficits of 500-750 calories per day being recommended for weight loss. While low-calorie diets often restrict fats or carbohydrates, neither has been definitively proven more effective for weight loss as long as a calorie deficit is maintained.
Meal timing is also an important factor; higher-calorie breakfasts combined with overnight fasting may help prevent obesity. Ultimately, there is no single best strategy for weight management.
The 21-Day Fix Program
The 21-Day Fix is a weight loss and exercise program marketed by Beachbody, promising to help individuals lose up to 15 pounds (7 kg) in just three weeks. The program includes a workout guide and a diet control plan. It's especially popular among Beachbody enthusiasts, with many testimonials and before-and-after photos showcasing its supposed effectiveness.
Components of the 21-Day Fix
Workouts: The program includes two DVDs featuring six 30-minute workouts:
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- Upper Fix: Resistance training for the upper body.
- Lower Fix: Designed to tone the lower body and burn fat.
- Total Body Cardio Fix: A full-body cardio workout with weights.
- Cardio Fix: A cardio workout without weights.
- Pilates Fix: A Pilates-based workout focusing on core strength.
- Yoga Fix: A yoga workout to improve flexibility and balance.
The workout schedule encourages users to complete at least one workout every day.
Diet Plan: The 21-Day Fix program focuses on controlling food portions using specific containers. In the introductory guide, a mathematical formula estimates calorie needs:
- Multiply current weight in pounds by 11 (calorie base or BMR).
- Add 400 calories (for exercise).
- Subtract 750 calories (deficit) to determine the target calorie intake.
This calculation determines a suitable plan and shows users how many servings of each color-coded food container they can consume each day. Each food container is sized differently and is used for a specific food group:
- Green container (1 cup): Vegetables
- Purple container (1 cup): Fruits
- Red container (3/4 cup): Protein sources
- Yellow container (1/2 cup): Carbs
- Blue container (1/3 cup): Healthy fats
- Orange container (2 tbsp): Seeds and dressings
Users are also allowed to consume between two to six teaspoons of nut butter and oils, depending on the plan package and customer goals.
Four "Container Plans" exist with different calorie target ranges:
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- Plan A: 1,200-1,499 calories
- Plan B: 1,500-1,799 calories
- Plan C: 1,800-2,099 calories
- Plan D: 2,100-2,300 calories
Progress Tracking: Those following the 21-Day Fix are encouraged to track their weight loss progress by taking "before" pictures and measuring body parts to assess how many inches have been lost after three weeks. After completing the program, "before" images and measurements are compared to "after" images and measurements to estimate total progress.
Foods Recommended on the 21-Day Fix
The 21 Day Fix program encourages healthy eating and emphasizes fresh produce, lean proteins and healthy fats. Examples of foods to eat include:
- Vegetables: Kale, watercress, collard greens, spinach, Brussels sprouts, broccoli, asparagus, beets, tomatoes, peppers, cauliflower, etc.
- Fruits: Blueberries, blackberries, strawberries, pomegranate, guava, star fruit, passion fruit, watermelon, cantaloupe, oranges, tangerines, apples, etc.
- Carbs: Sweet potato, plantains, quinoa, beans, lentils, edamame, cassava, peas, nonfat refried beans, brown rice, potatoes, buckwheat, amaranth, etc.
- Proteins: Sardines (fresh or canned in water), skinless chicken or turkey breast, lean ground chicken or turkey (≥93% lean), fish (cod, salmon, tuna, catfish, tilapia, trout), whole eggs, egg whites, 1% greek yogurt, Shakeology, tofu, etc.
- Healthy fats: Avocados, almonds, cashews, peanuts, pistachios, walnuts, pecans, hummus, coconut milk and cheeses (feta, goat, cotija and parmesan).
- Seeds and dressings: Pumpkin seeds, sunflower seeds, sesame seeds, ground flax seeds, olives and 21 Day Fix dressing recipes.
- Oils and nut butter: Extra-virgin olive oil, extra-virgin coconut oil, flaxseed oil, walnut oil, pumpkin-seed oil, nut butter (peanut, almond, cashew, etc.) and seed butter (pumpkin, sunflower, tahini).
- Seasonings and condiments: Lemon or lime juice, vinegar (cider, white wine, or red wine), mustard, herbs, spices (except salt), garlic, ginger, unsweetened hot sauce, flavor extracts and 21 Day Fix seasoning mix recipes.
- Approved beverages: Water, fruit-infused water, sparkling water, coffee, green tea and unsweetened iced tea.
Three times a week, dieters can replace one carbohydrate portion with an approved treat, such as dried fruit, dark chocolate chips or a cookie made using a 21 Day Fix recipe that’s included in the package.
Foods to Avoid on the 21-Day Fix
Though the 21 Day Fix package does not explicitly state that certain foods are off limits, it advises only consuming approved foods. As a whole, the Beachbody organization discourages unhealthy foods and emphasizes nutrient-dense foods for those following their nutrition programs. When following Beachbody nutrition programs, the following are not recommended:
- Added sugars: Sugary beverages, sweetened yogurts, candy, baked goods, table sugar, etc.
- Refined carbs: White pasta, sugary cereals, white bread, bagels, white rice, corn chips, tortillas, etc.
- Processed foods: Fast food, processed meats (hot dogs, deli meats, bacon), packaged snacks, canned foods packed in syrup, energy bars, etc.
- Greasy and fried foods: Fried chicken, French fries, potato chips, burgers, pizza, deep-fried foods, etc.
- Alcohol: Beer, wine, liquor, etc.
Potential Benefits of the 21-Day Fix
- May Help You Lose Weight: The 21 Day Fix meal plan suggests several practices proven to promote weight loss, such as cutting out added sugars and processed foods. Individuals following the 21 Day Fix are guided to eat a fiber-rich diet and drink plenty of water, all of which have been shown to be particularly effective for promoting weight loss.
- Supports Healthy Eating: The foods emphasized on the 21 Day Fix meal plan are healthful, nutrient-dense options including vegetables, good carbs, and protein. The color-coded containers ensure participants consume a variety of nutritious foods from different food groups each day. Unlike weight loss plans that recommend processed, nutrient-poor foods like fast food, frozen dinners, and packaged snacks, the 21 Day Fix encourages whole, healthy foods.
- Containers Teach Portion Control: Using the color-coded containers is an easy way to control portions and may deter dieters from overeating, which may aid weight loss.
- Exercise Is Part of the Program: The 21 Day Fix includes a three-week exercise program with 30-minute workouts targeting different body areas. Since the program emphasizes daily exercise, participants are likely to continue physical activity after the three-week period, creating a healthy lifestyle.
Potential Drawbacks of the 21-Day Fix
- The Focus Is on Short-Term Weight Loss: As indicated in the name, the 21 Day Fix program focuses on a short-term, three-week duration. Customers can indeed lose weight while following this plan, but there is a high likelihood of regaining the weight once the program is over. Any successful weight loss plan should focus on gradual, sustainable changes over time rather than rapid fat loss.
- Beachbody Pushes Dieters to Purchase Supplements: Within the Beachbody meal plan, dieters are urged to purchase Beachbody products like Shakeology protein shakes and supplements.
- May Be Too Restrictive for Some: The 21 Day Fix program focuses on controlling food portions using specific containers. While this can be an effective way to prevent overeating, relying on these containers and counting calories may be inconvenient for some people. Moreover, this is not a realistic long-term solution, and constantly monitoring portions and food intake could lead to disordered eating patterns in some individuals.
- Dieters Determine Their Own Calorie Needs: A major flaw in the 21 Day Fix program is that dieters must calculate their own calorie needs. For example, using the calorie calculation formula from the 21 Day Fix, someone weighing 145 pounds (66 kg) would only consume 1,245 calories during the program. This is a very low caloric intake, especially for those with busy, physically demanding jobs. Eating too few calories while engaging in intense activity can lead to hypoglycemia (low blood sugar) and mood changes leading to loss of appetite.
The Mayo Clinic Diet
The Mayo Clinic Diet is the official weight-loss program developed by Mayo Clinic experts. It focuses on eating delicious healthy foods and increasing physical activity. The program emphasizes that the best way to keep weight off for good is to change your lifestyle and adopt new habits that you enjoy and can stick with. It focuses on changing your daily routine by adding and breaking habits that can affect your weight. Simple habits, such as eating more fruits and vegetables, not eating while you watch TV, and moving your body for 30 minutes a day, can help you lose weight.
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Phases of the Mayo Clinic Diet
- Lose It!: This two-week phase is designed to jump-start your weight loss, so you may lose up to 6 to 10 pounds (2.7 to 4.5 kilograms) in a safe and healthy way. In this phase, you focus on lifestyle habits that are associated with weight. You learn how to add five healthy habits, break five unhealthy habits and adopt another five bonus healthy habits.
- Live It!: This phase is a lifelong approach to health. In this phase, you learn more about food choices, portion sizes, menu planning, physical activity, exercise and sticking to healthy habits. You may continue to see a steady weight loss of 1 to 2 pounds (0.5 to 1 kilograms) a week until you reach your goal weight.
Key Principles of the Mayo Clinic Diet
- Portion Control and Meal Planning: The Mayo Clinic Diet makes healthy eating easy by teaching you how to estimate portion sizes and plan meals. The program doesn't require you to be precise about counting calories.
- Healthy Weight Pyramid: Mayo Clinic experts designed the Mayo Clinic Healthy Weight Pyramid to help you eat foods that are filling but low in calories. Each of the food groups in the pyramid emphasizes health-promoting choices.
- Physical Activity: The program recommends getting at least 30 minutes of physical activity every day and even more exercise for further health benefits and weight loss. It provides an exercise plan with easy-to-follow walking and resistance exercises that will help maximize fat loss and boost mental well-being.
- Customization: The Mayo Clinic Diet provides a choice of five different eating styles at several calorie levels. You can have sweets but no more than 75 calories a day. For practicality, consider thinking of your sweets calories over the course of a week.
Safety and Considerations
The Mayo Clinic Diet is generally safe for most adults. For most people, eating lots of fruits and vegetables is a good thing - these foods provide your body with important nutrients and fiber. Also, the natural sugar in fruit does affect your carbohydrate intake - especially if you eat a lot of fruit. This may temporarily raise your blood sugar or certain blood fats. If you have diabetes or any other health conditions or concerns, work with your doctor to adjust the Mayo Clinic Diet for your situation. For example, people with diabetes should aim for more vegetables than fruits, if possible.
The Food Lovers Fat Loss System
The Food Lovers Fat Loss System is touted as the no-diet weight loss plan for people who love to eat. Developed by a company called Provida with certified nutritionist Robert Ferguson, MS, it is a relatively simple diet plan focused on pairing the right foods and eating every few hours. Dieters learn about fast and slow carbs and how to pair them with lean protein and healthy fats on the Fat Loss Plate. Dieters can expect to lose up to 3 pounds per week, depending on starting weight.
Key Components
The 21 Day Metabolism Makeover: The plan starts with this, followed by the Food Lovers for Life long-term maintenance diet plan. Each day, the plan unveils a simple diet strategy to help dieters develop healthy lifestyle habits that support long-term weight loss. Habits like keeping a food, water and exercise log, eating breakfast, controlling sodium, choosing healthy fats, drinking lots of water, finding a buddy, eating more fiber, and getting enough sleep are just a few examples.
The Fat Loss Plate: Dieters eat three meals and snacks every 2-3 hours using the Fat Loss Plate with approved foods in proper portions. Most meals contain about 15 grams of protein and 30 grams of carbs and total calories vary but are never less than 1,200 for women and 1,500 for men.
Hydration: Dieters are instructed to drink 12 8-ounce glasses of water daily, plus 8 ounces for each 20 minutes of exercise.
Portion Control: No counting calories or fat grams, but portions are controlled. There are three versions of the fat loss plate to choose from:
- Version A: 1 protein +1 fast carb + 1 slow carb (Spaghetti and meatballs with a side salad)
- Version B: 1 protein +3 slow carbs (Entree salad with grilled chicken)
- Version C: 1 protein and 1 fast carb (turkey sandwich)
One tablespoon of healthy fat is allowed per meal only with lean protein and low-fat fast carbs. For the first five days, snacks are either one portion of a whole food such as an apple or any food that doesn't exceed 150-250 calories. "Accelerator snacks," which are recommended starting on day 6, must also contain at least 7 grams of protein.
Recommended Foods
The plan involves using the "fat loss plate" in one of three variations. Here are the recommended foods to choose to make a healthy fat loss plate:
- Lean protein: pork tenderloin, sirloin steak, extra lean ground beef, skinless poultry breast, fish, low-fat dairy, and eggs
- Fast carbs: pasta, couscous, potatoes, bagels, English muffins, rolls, blueberries, cherries, grapes, apples, and dried fruits
- Slow carbs: artichokes, carrots, peppers, tomatoes, zucchini, green beans, broccoli, eggplant, asparagus, squash, raspberries, strawberries, blackberries, lemons, limes, and legumes
- Free carbs: bok choi, cabbage, cauliflower, celery, cucumbers, onions, chili peppers, lettuce, mushrooms, radishes, spinach, and sprouts
- Fats: butter, peanut butter, cream cheese, mayonnaise, cheese, bacon, sausage, light salad dressing, nuts and seeds
Limited amounts of coffee, tea, diet drinks, and club soda are allowed.
Foods to Avoid
Foods not recommended because, according to the plan, they are likely to slow metabolism: white, bleached, and enriched flours; alcohol; soda; saturated fats; trans fats; partially hydrogenated oils; high fructose corn syrup and other sugars; foods high in sodium; and most processed foods.
Maintenance Phase
The plan's five-week Food Lovers for Life phase is a little more liberal. It's a maintenance plan that follows the three-week initial phase. Alcohol, refined flour, sugar, and fried foods are allowed in this phase but are strongly discouraged. For example, instead of eating deep-fat-fried foods, dieters are encouraged to eat oven-fried foods.
Expert Opinions
Marisa Moore, MBA, RD, LD, a spokeswoman for the Academy of Nutrition and Dietetics (formerly called the American Dietetic Association), says, "There are lots of good aspects to the Food Lovers Fat Loss System, but it is gimmicky and makes unrealistic promises like your metabolism will be faster or more efficient after 21 days, which is not grounded in scientific evidence."
Ron Dudek, PhD, an obesity and diabetes researcher at East Carolina University, says, "The real important part of the eating plan is the reduction in the amount of carbohydrates and learning to make a Fat Loss Plate, the rest is frosting on the cake."
Supplements
The plan recommends taking a daily multivitamin, which may be needed to cover nutrient shortfalls. It also recommends, but does not require, certain "fat loss" supplements, including omega-3 fatty acids, flaxseed, and protein powder. However, experts say those supplements do not optimize metabolism or promote fat loss.
General Dietary Strategies for Weight Management
Beyond specific diet plans, several general dietary strategies are recognized as effective for weight management:
- Low-Calorie Diets: A low-calorie diet involves consumption of 1,000-1,500 calories per day. Deficits of 500-750 calories per day have been used for weight loss. Low-calorie diets typically restrict fats or carbohydrates.
- Macronutrient Composition-Based Diets: Some diets focus on specific macronutrient ratios. For example, low-carbohydrate diets restrict carbohydrate intake to below 45%-65% of total daily energy. Ketogenic diets restrict carbohydrate intake to less than 10% of total daily energy, inducing nutritional ketosis. High-protein diets increase protein intake to 30% of total daily calories or 1-1.2 g/kg of ideal body weight per day.
- The Mediterranean Diet: This diet involves high intake of fruits and vegetables, poultry, fish, and dairy products, and little to no consumption of red meat. The effectiveness of the Mediterranean diet for weight loss and preventing cardiovascular disease is supported by sufficient evidence.
- The Paleolithic (Paleo) Diet: This diet advises consuming lean meat, fish, vegetables, fruits, and nuts while avoiding grains, dairy products, processed foods, and added sugar and salt.
- The New Nordic Diet: This diet is based on unprocessed whole grains, high-fiber vegetables, fish, low-fat dairy foods, lean meat of all types (beef, pork, lamb), beans and lentils, fruit, dense breads, tofu, and skinless poultry.
- Vegetarian Diets: These diets exclude meat, fish, and poultry, but there are many variations of the diet, including lactovegetarians and lacto-ovo-vegetarians.
- The Dietary Approaches to Stop Hypertension (DASH) Diet: The DASH plan includes many vegetables, fruits, and grains with an emphasis on whole grains. Low-fat or non-fat dairy foods, pulses, nuts, seeds, lean meats, poultry, and seafood are also allowed.
- The Portfolio Diet: This diet recommends daily consumption of 2 g of plant sterols, 50 g of nuts, 10-25 g of soluble fibers from plant foods, and 50 g of soy protein; meat, poultry, seafood, dairy, and eggs are not allowed.
- Intermittent Fasting: Intermittent fasting involves regular periods with no or very limited calorie intake, focusing on the time window of eating instead of calorie calculations or macronutrient composition.
The Importance of Meal Timing
Meal timing and the circadian rhythm have raised a novel issue in weight management. Eating late can cause circadian disruption, resulting in production of free cortisol, changes in daily rhythms of body temperature, decreased resting energy expenditure, and decreased glucose tolerance.