The Danish Diet

It goes by many names: the Danish diet, the Denmark diet and even the very official Royal Danish Hospital diet. But no matter what it's called, the Danish diet is nothing more than a fad diet. You may lose weight quickly following this very low-calorie limited diet plan, but you may struggle to keep the weight off.

According to various sources on the internet, the Danish diet was created by a doctor at a hospital in Denmark to produce quick weight loss in patients with morbid obesity before they had surgery. The diet is meant to be a very short-term plan and conducted under medical supervision. But no hospital or doctor in Denmark has claimed to be the creator of the Danish diet.

This sounds a lot like another popular fad diet, the seven-day Sacred Heart diet, which is a soup-based diet purportedly developed by a hospital for their cardiac unit. But like the Danish diet, no hospital has laid claim to this low-calorie, limited diet either.

And for the record, most doctors and other health care professionals wouldn't recommend a very low-calorie diet that may be lacking in key nutrients before a surgical procedure. For a smooth recovery, the American Society of Anesthesiologists suggests eating a healthy diet prior to your surgery. Filling your diet with nutrient-rich foods provides your body with the resources it needs to handle both the stress and healing following any surgical procedure.

​Read more:​ 9 Unhealthy, Even Dangerous Weight-Loss Diets

What do you get to eat on the Danish diet? Well, not too much. While there are many versions of the Danish diet, in general, you're limited to only two food groups — protein and vegetables, with few choices from either group. The Danish diet cuts out all fruit, whole grains and dairy foods, although you may find some versions of the plan that include unsweetened plain yogurt and rye bread.

The types of foods allowed on the diet include:

• Water, unsweetened black tea or coffee
• Lean proteins such as beef, lamb, poultry and eggs
• Low-carb vegetables such as tomatoes, spinach, celery and cauliflower

While following the diet, you're encouraged to eat three meals a day at very specific times, without any snacks. If you get hungry between meals, the diet suggests you drink water. You're discouraged from eating after 6 p.m. and are not allowed to indulge in any foods not on the plan.

A typical Danish diet menu may include:

• Breakfast by 8 a.m. consisting of black coffee and water
• Lunch at 1 p.m. with 5 to 7 ounces of lean meat or two eggs and 1/4 to 1 cup of vegetables
• Dinner at 6 p.m. with 5 to 7 ounces of lean meat and 1/4 to 1 cup of vegetables

You're only supposed to follow the diet for 13 days.

It shouldn't be too hard to guess why you lose weight following the Danish diet. It's because it's very low in calories. It is estimated that you eat about 600 calories a day following the Danish diet. According to the National Heart, Lung and Blood Institute, you shouldn't follow any weight-loss diet that provides fewer than 800 calories without being monitored by a doctor.

Most men and women can lose weight limiting their calorie intake to 1,200 to 1,800 calories a day. The number of calories you need to lose weight depends on your age, gender, body composition and activity level. If you're not sure how many calories you need to lose weight, consult with a registered dietitian.

​Read more:​ Recommended Caloric Intake for Weight Loss

Not getting enough calories can affect your metabolism and your health. The calories you eat provide your body with energy. Most of those calories are used to run systems you don't even think about, like digestion, heart rate and brain function. This is referred to as your resting metabolic rate (RMR).

If you're not eating enough calories to support these basic bodily functions, then your body goes into what's referred to as ​preservation mode​, slowing things down so you're not burning as many calories. Essentially, when you limit your calorie intake to 600 calories a day, you sabotage your weight loss by slowing down the system that burns the calories. While activity is a good way to up your body's calorie-burning power, you probably won't have the energy needed to sustain any planned exercise to give your metabolism that much-needed boost.

The very limited meal plan also makes it difficult for you to get all the vitamins, minerals and other nutrients your body needs to carry out important functions. Not getting all the nutrients your body requires may affect how you feel, as well as your overall health. Headaches, constipation, fatigue and difficulty concentrating are common symptoms of a low-calorie diet.

​Read more:​ The Best Way to Lose Weight in One Month

The effect it has on your metabolism isn't the only problem with such a low-calorie diet. Another reason fad diets like the Danish diet don't work is because they're not long-term plans. You most certainly will lose weight limiting your intake to 600 calories a day, but when you lose a lot of weight quickly, it's most likely water weight and muscle mass, not fat.

These factors make keeping the weight off very difficult. If you go back to your usual way of eating after you've lost the weight on the Danish diet, you'll probably regain the weight, and probably a few extra pounds, too.

To lose weight and keep it off, you need to stop thinking about quick results and instead focus on making changes that can give you lasting results.

The Danish diet may help you lose weight, but you won't keep it off if you don't have a plan for what you're going to do after the 13 days. There's no one weight-loss diet that works for everyone. If you're struggling, consult with a registered dietitian who can devise an individualized plan that not only meets your nutritional needs and weight-loss goals, but also takes into consideration your lifestyle and medical history.

If you want to be successful at losing weight, consider the tactics used by the participants in the National Weight Control Registry (NWCR), which is a registry that tracks people who have lost a significant amount of weight — more than 30 pounds — and have kept it off for a year or more. According to the NWCR researchers, people who have lost weight successfully do these things:

• Eat breakfast daily.
• Exercise no less than 60 minutes most days of the week (most participants walk).
• Weigh themselves each week.
• Watch less than 10 hours of television a week.

Referred to as the New Nordic Diet (NND), this diet plan was developed by food professionals and chefs from the Nordic countries, including Denmark, Sweden, Finland, Norway and Iceland. Often referred to as the next Mediterranean diet, NND is filled with vegetables, fruits, fish, game meats, whole grains and some dairy.

In addition to being filled with healthy, nutritious foods, NND also supports weight loss. A June 2016 study published in the Journal Proteome Research found that the NND was significantly better at promoting weight loss than the average Danish diet. The researchers concluded that a diet filled with fish, vegetables, fruits and whole grains helped promote weight loss by improving insulin sensitivity and increasing the use of fat as fuel during the fasting state.