Single-Food Weight Loss Diets You Should Avoid At All Costs

While strawberries are indeed a nutritious fruit, relying solely on them for an extended period is not a balanced approach to nutrition, which is what the strawberry diet proposes. Like most single-food diets, the strawberry diet gained attention for its promises of rapid weight loss. In fact, it claims to help people shed 4 pounds in just four days by severely limiting calorie intake (per Diets Meal Plan). Nevertheless, it falls short in terms of promoting sustainable eating habits. 

The strawberry diet has no specific guidelines or instructions, and it is available in two different forms. One of the most extreme versions of this diet is the strawberry-only variation, where dieters are supposed to consume only one meal of strawberries daily (via Livestrong). In contrast, the more lenient version, known as the strawberries-at-each-meal version, permits roughly 1,200 calories daily, incorporating strawberries into every meal and featuring strawberry smoothies or yogurt with strawberries as snacks. In addition to the fruit, the site explains that this version allows for a limited selection of other foods, such as lean proteins (turkey, low-fat cottage cheese, and chicken breast), fresh fruits (apples and bananas), vegetables (asparagus, cucumber, and lettuce), and even a baked potato. Regarding beverages, unsweetened tea and coffee are also allowed. 

Per Livestrong, the diet justifies its strict regimen by highlighting the nutritional benefits of strawberries, including fiber, vitamin C, and antioxidants. However, its severe calorie restriction raises concerns, as a diet so low in calories can lead to a lack of energy, nutrient deficiencies, and numerous additional potential side effects (via Healthline).

There are different versions of the apple diet, depending on where you look. Essentially, this diet offers two variations — a brief five-day plan and a more extended month-long program — both claiming to facilitate balanced weight loss. The 5-Day Apple Diet presents itself as a balanced approach to weight loss, allowing for a daily caloric intake ranging from 1,000 to 2,000 calories (via Healthy Natural Diet). The first day of this regimen suggests consuming only apples; and, over the next four days, additional foods are gradually introduced, including vegetables, whole-grain bread, and low-fat foods like lean protein sources, milk, and cheese. In contrast, the long version spans four weeks and includes two non-consecutive days of apple detox. During these detox days, dieters may consume five apples regularly with a glass of skimmed or soy milk and a small serving of plain yogurt as a snack. Tea, coffee, and water are permitted as well. To add an element of flexibility, the plan includes a weekly cheat day, during which people can indulge in any food of their choice while abstaining from apples (per Good to Know).

Regardless of the variation, the apple diet claims to achieve weight loss by cleansing the body and enhancing metabolism based on the belief that the health benefits of apples can lead to weight loss. Still, while apples are highly nutritious and can boost immunity, heart, and metabolic health and even support weight loss (via Healthline), no evidence suggests that you should rely solely on them to achieve better health.

According to Medical News Today, the egg diet is a high-protein, low-carbohydrate, low-calorie diet available in three distinct versions, all of which emphasize eggs as the primary source of protein, which can be prepared in various ways like boiled, poached, or scrambled. In its traditional form, the egg diet allows the consumption of eggs alongside lean proteins; low-carb vegetables like kale, broccoli, and spinach; and some fruits. Another variation, known as the egg and grapefruit diet, aligns with the traditional version but introduces half a grapefruit with each meal. The most extreme iteration permits only eggs and water at every meal.

Per a 2017 study published in Nutrition and Dietetics, high-protein diets are promising for their potential to facilitate weight loss. However, the egg diet's exclusivity in promoting egg consumption as the primary source of protein needs more scientific evidence to support its efficacy. While eggs are indeed rich in protein, vitamins, and minerals, they notably lack dietary fiber, an essential component for overall health; and, since grains are also banned from this diet, it may be challenging to obtain an adequate fiber intake through the limited permitted dietary sources (per Healthline). Moreover, since the diet enforces strict restrictions, it tends to yield short-term weight loss results but may not offer a viable solution for long-lasting weight control (per Medical News Today).

There is no single official soup diet. Instead, there are several variations with their own rules and guidelines, typically lasting 10 days at most. Thus, their main purpose is to provide a quick weight-loss solution. Some of these diets revolve around consuming soup as the sole component of meals, while others permit a limited selection of supplementary foods (via Healthline).

Per the site, one popular example is the broth-based soup diet, which lasts seven days, excludes cream-based soups, and focuses on broth-based soups with vegetables and lean protein sources. Another variation is the bean soup diet, which emphasizes Dr. Greger's Champion Vegetable Bean Soup and is complemented by other fat-free, plant-based foods. However, high-fat or calorie-dense foods like nuts are banned to optimize weight loss results. Then there's the cabbage soup diet, which also follows a seven-day plan featuring a chicken- or vegetable-broth-based soup with cabbage and other low-carb vegetables. Finally, the chicken soup diet is another seven-day weight loss regimen that prioritizes chicken soup for most meals, with breakfast being the only non-soup meal of the day. Other similar soup diets include the keto and Sacred Heart soup diets.

Healthline explains that soup diets can be advantageous as they promote increased vegetable, fiber, and water consumption while encouraging plant-based eating, which is associated with numerous health benefits. However, the short-term nature of these diets limits their potential for long-term benefits while carrying the risk of reducing your metabolic rate, making sustained weight loss challenging. Plus, their severe calorie restriction can lead to side effects like dizziness, weakness, and fatigue.

The tuna diet is a single-food diet created by bodybuilder Dave Draper. It is a short-term, low-calorie, low-carb, and high-protein diet that centers around the intake of plain canned tuna and water for rapid weight loss (per Healthline). During the first three days of the diet, people are meant to eat 1.5 grams of protein per kilogram of body weight daily. Then, during the second phase, low-fat dairy products, fruit, poultry, and vegetables are introduced, with a recommended macronutrient ratio of 40% protein, 30% carbohydrates, and 30% fat for as long as it takes you to reach your desired weight. To complement the tuna-centric meals, the diet prescribes consuming 2 liters of water, a serving of Metamucil for fiber, and various vitamin, mineral, and branched-chain amino acid supplements. The need to add essential nutrients from artificial sources highlights the nutritionally unbalanced nature of the diet.

While the tuna diet may lead to rapid weight loss due to its extreme calorie restriction, it has the potential to result in nutrient deficiencies as it eliminates fats, sugars, and carbohydrates. Plus, as registered dietitian Samantha Coogan, MS, RD, explains via Greatist, since carbs are the brain's main energy source, this could lead to adverse effects on brain health, causing symptoms like tiredness, disorientation, sluggishness, and difficulty concentrating. Moreover, excessive tuna consumption can lead to mercury poisoning, and given the substantial tuna consumption in this diet, the site warns about the likelihood of exceeding recommended mercury limits by following this diet.

Being arguably the most restrictive single-food diet on this list, the potato diet is a short-term dietary plan lasting three to five days, during which dieters are limited to consuming potatoes as their exclusive source of food. Per Healthline, this diet proposes rapid weight loss results, with claims of shedding up to 1 pound per day. While the diet is not backed up by research, proponents of the potato diet suggest that it can boost your immune system and gut health and sustain energy levels while facilitating weight loss.

Like most single-food diets, there are variations of the potato diet. Some allow the use of herbs, spices, and oils to season the potatoes — which can be prepared by boiling, baking, or mashing — as long as you stay away from fried potatoes or chips (via Good to Know). Conversely, per Healthline, other versions advocate for plain potatoes without salt or condiments. However, a common factor is the prescribed daily potato consumption, which ranges from 2-5 pounds. Plus, sweet potatoes or yams are not permitted, and heavy exercise is also discouraged during this diet. According to Healthline, while the potato diet may yield short-term weight loss, it is not considered a sustainable long-term solution. Despite being nutritious, potatoes lack essential nutrients, including protein and healthy fats. Thus, relying solely on potatoes for an extended period can lead to nutrient deficiencies and muscle loss.

The Cereal Diet proposes eating low-calorie cereals with low-fat milk to help you lose weight. Its primary goal is to create a calorie deficit, ultimately promoting weight loss by significantly reducing overall daily caloric intake while considering simplicity, convenience, and affordability. Per Healthline, the diet's core principle involves replacing breakfast and lunch with a serving of low-calorie cereal and milk, typically less than a cup. For dinner and snacks, it recommends small portions of healthy meals that are low in calories and incorporate lean protein, whole grains, fruits, and vegetables.

One potential benefit of the cereal diet is that it provides fiber and whole grains (if you choose your cereals wisely). However, it has its fair share of downsides. For instance, some cereal choices can be high in added sugars, which raises concerns about the diet's nutritional quality and impact on overall health. Moreover, it is not considered a sustainable or balanced approach to weight loss, as it may fall short of providing essential nutrients, particularly adequate protein and healthy fats, which may lead to increased hunger and cravings (via All Simple Healthy). Lastly, Healthline notes that, despite some people reporting having experienced weight loss on this diet, it most likely happened primarily due to the calorie restriction it imposes, which means that it can easily be regained once you're off the diet. 

If you're looking for a more comprehensive and sustainable approach to weight management, try following a well-rounded approach that provides all necessary nutrients through natural and wholesome food sources, such as the Mediterranean or DASH diets.

If you need help with an eating disorder, or know someone who does, help is available. Visit the National Eating Disorders Association website or contact NEDA's Live Helpline at 1-800-931-2237. You can also receive 24/7 Crisis Support via text (send NEDA to 741-741).