The egg diet is a low-carbohydrate, low-calorie, but protein-heavy diet. It’s designed to help aid in weight loss without sacrificing the protein needed to build muscles. Like its name suggests, it emphasizes the consumption of eggs as a main source of protein.

The egg diet has multiple versions, but in each you can only drink water or zero-calorie beverages. Foods high in carbohydrates and natural sugars, like most fruits and all breads, pastas, and rice are eliminated from the diet, which typically lasts 14 days. You only eat breakfast, lunch, and dinner. There are no snacks, aside from water or other zero-calorie drinks.

While there are several different versions of the egg diet, they all work primarily the same. You’ll start each day with eggs, and you’ll continue to eat small portions of lean protein through the day.

Lean protein includes:

  • eggs
  • chicken
  • turkey
  • fish

Fruits and vegetables you can eat include:

  • grapefruit
  • broccoli
  • asparagus
  • zucchini
  • mushrooms
  • spinach

In the traditional version of the egg diet, you’ll eat eggs or another source of lean protein like chicken or fish at every meal. Low-carb veggies or grapefruit are included in breakfast and dinner. A sample meal plan would include:

  • Breakfast: 2 boiled eggs and 1 grapefruit, or a 2-egg omelet with spinach and mushrooms
  • Lunch: 1/2 roast chicken breast and broccoli
  • Dinner: 1 serving of fish and a green salad

Another version of the egg diet is the egg and grapefruit diet, where you’ll eat one-half of a grapefruit with each meal (instead of it being optional twice a day). A meal plan from this version of the diet would include:

  • Breakfast: 2 boiled eggs and 1/2 grapefruit
  • Lunch: 1/2 roast chicken breast, broccoli, and 1/2 grapefruit
  • Dinner: 1 serving of fish and 1/2 grapefruit

The final version of the egg diet, which is less common, is the “extreme” egg diet. In this version, people only eat hard-boiled eggs and drink water for 14 days. This diet is not recommended, as it’s extremely imbalanced and can cause malnourishment.

The most common unwanted side effect of the egg diet is the lack of energy many people will feel from the depletion of carbs. This makes it difficult to exercise.

Suddenly shifting to a high-protein, low-carb diet can also be difficult for the digestive system to adjust to. You may experience nausea, constipation, flatulence, and bad breath as a result.

Eggs are also very high in cholesterol with 186 grams, or 63 percent of the daily recommended value. However, research has shown that it’s not the cholesterol in foods to worry about for heart health, but rather saturated and trans fats.

A 2015 study reported that men who consumed more than six eggs per week had a 30 percent higher risk of heart failure. They also had a higher risk of ischemic stroke. Eating six eggs or less per week in either men or women had no impact on hemorrhagic stroke, myocardial infarction, or heart failure.

Because eggs have no fiber, you’ll need to be careful to include other foods that do have ample amounts. This way, you won’t temporarily impair bowel function or starve your healthy gut bacteria.

Because this type of diet is not sustainable, many people revert back to old eating habits as soon as it’s over. They’ll likely gain the weight back, if not even more. This can lead to yo-yo dieting, which isn’t healthy.

The general consensus in the medical communities is that the egg diet isn’t the safest way to lose weight.

If you’re following any version of the egg diet, your calories will come in at under 1,000 calories a day. According to Harvard Medical School, it’s unsafe for women to consume less than 1,200 calories a day and for men to consume less than 1,500 unless supervised by a medical professional.

Eating up to seven eggs a week, or more in some studies, seems to be safe for the general population, with no seeming effect on cardiovascular risk. Doing so may actually reduce stroke risks. A 2015 study confirmed that even some people with diabetes can eat eggs more liberally than previously believed, about 12 per week, without worsening cholesterol levels or blood sugar control.

That said, a high-protein, low-carbohydrate diet may be associated with higher risks of cardiovascular disease, according to one study. The disadvantage of this particular study is that it didn’t control or emphasize types of carbohydrate or protein sources, which could significantly influence the study outcome.

Eating enough fiber every day is crucial to nourishing gut bacteria. Americans already get far below the daily recommended fiber intake. Since fiber is primarily found in legumes, fruits, vegetables, nuts, seeds, and whole grains, the egg diet could complicate an already low fiber intake.

Any type of extreme crash diet designed to help with sudden weight loss might work if you can stick to it. However, such diets normally come with the trade-off of unhealthy consequences. The egg diet isn’t sustainable, and most people who follow it will put the weight back on almost as soon as they resume a normal diet. It’s more effective to increase exercise and choose well-balanced meals that limit calories, high-sugar foods, and processed foods.