Obesity is common, serious, and costly, the Centers for Disease Control and Prevention tells us. But what is the best approach to weight loss? The answer seems to be a gradual approach that is consistent over time. Extreme caloric restriction, or “crash dieting,” can have dangerous consequences for your physical and mental health, and you may be more likely to gain the weight back.

The problems of crash dieting

The concept behind TV shows like The Biggest Loser is intriguing. Go hard for a couple months, lose the weight, problem solved. But, The New York Times published an article detailing how the show’s contestants lost hundreds of pounds during one season of the show, but gained the weight back over the course of six years.

Researchers studied the contestants and published their findings in the journal Obesity. They concluded that the contestants were essentially fighting against their own biology, because their resting metabolisms had slowed dramatically and were causing them to gain weight back.

The contestants started the show with normal metabolisms for their size, but by the time the show ended, their metabolisms had slowed considerably and did not recover, even years later.

This is one of the most common problems with rapid weight loss.

“The body can go into starvation mode when you overly restrict your calorie intake. This is the body’s effort to conserve energy,” said Amy Campbell, CDE, registered dietitian, and the author of several books about diabetes. “As a result, your metabolic rate can decrease, making it harder to lose weight.”

She also notes that rapid weight loss can put you at risk for nutrient deficiencies, such as potassium, calcium, or fiber, and can decrease muscle mass because your body will burn lean muscle mass for energy.

“Most diets that promote fast weight loss aren’t sustainable,” Campbell said. “They don’t teach you anything about nutritious eating or how to keep the weight off long term. Not surprisingly, it’s common to regain any weight lost, and then some, once you stop the diet.”

Crash diets may also may pose more risks to your health than gradual weight loss. They can weaken your immune system and increase your risk of dehydration, heart palpitations, and cardiac stress.

“A crash diet once won’t hurt your heart,” cardiologist Isadore Rosenfeld, MD, told CNN Health. “But crash dieting repeatedly increases the risk of heart attacks.”

Rapid weight loss can also take a toll on your mental health, Campbell said.

“Psychologically, crash diets can leave you feeling irritable, anxious, and fatigued,” she said.

The role of support

Once you lose weight, having a strong support network can be a major factor in helping you to keep weight from coming back.

Robert Huizenga, the doctor on The Biggest Loser, told The New York Times that a lack of social support may have contributed to the contestants regaining weight as well.

“Unfortunately, many contestants are unable to find or afford adequate ongoing support with exercise doctors, psychologists, sleep specialists, and trainers—and that’s something we need to change,” he told the Times.

There are a lot of ways to get support, including joining a support group, joining a commercial program like Weight Watchers, engaging in online communities, using social media, or starting your own blog. You may find that working with a dietitian or a health coach is beneficial, and studies do support the benefits of this, she noted.

“Studies show that, especially for women, social support is very important for helping to keep weight off,” Campbell said. “Being able to connect and share experiences with people who have also gone through the weight loss process can definitely help people with weight control.”

“It’s difficult to lose weight, and even more difficult to keep it off,” Campbell added. “Not having support lowers your chances of being successful.”

Keeping weight off

Campbell said some of the best advice for long-term weight maintenance comes from the National Weight Control Registry, a database of thousands of people who have lost at least 30 pounds and kept the weight off for at least one year.

Some of their tips, based on actual success stories, include:

• Following a low-calorie eating plan (about 1300-1700 calories per day, you can calculate the right number of calories for you with an online calculator)
• Eating about the same time every day and eating four to five times a day, including eating breakfast daily
• Exercising 60 to 90 minutes a day
• Weighing yourself weekly or even daily
• Limiting TV viewing to less than 10 hours/week

Most experts recommend losing just one to two pounds a week, using a combination of diet and exercise. Your diet should limit saturated fats and sugars and instead promote fruits, vegetables, lean meats, fish, and whole grains, according to CNN Health.

Have you tried crash dieting? What are your tips for keeping weight off? Share your thoughts below.