A 1,000 calorie diet plan is an eating strategy that drastically cuts the number of calories a person consumes each day. However, drastically cutting calories does not typically result in sustained weight loss and may be harmful.

Extreme diets have undesirable effects and do not result in sustained weight loss. Instead, it is better to reach a moderate weight gradually with a balanced diet that a person can follow long term.

This article discusses 1,000 calorie diets, their safety, and their effectiveness. It also includes some tips for safe weight loss.

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A 1,000 calorie diet plan is an eating strategy that drastically cuts the number of calories an individual consumes each day. Experts consider this type of diet dangerous because they provide significantly fewer calories than the average adult needs for health and well-being.

People may turn to 1,000 calorie diets when they are desperate to lose weight quickly, such as before a vacation. While adults could follow this type of diet relatively safely for a couple of weeks, it is not something that doctors advise for extended periods.

A large body of research shows that when people do not eat a balanced diet with sufficient calories for their needs, it can harm health and trigger rebound weight gain.

Learn more about the recommended daily calorie intake here.

Dieting can have harmful outcomes and typically has more risks than benefits. Research associates dieting with long-term weight gain and the possibility of developing eating disorders.

When a person has an eating disorder, their eating habits can damage their physical health and ability to live a regular life.

Doctors associate eating disorders, such as binge-eating disorder, anorexia nervosa, and bulimia nervosa, with various medical issues. These include heart disease and endocrine problems.

Studies also show that the prolonged semi-starvation caused by continuous dieting can lead to severe depression, emotional distress, and irritability.

Once individuals return to a non-dieting state, they may experience a loss of control over their eating habits and develop a strong desire to eat more.

Learn the difference between anorexia and bulimia here.

Help is available

Eating disorders can severely affect the quality of life of people living with these conditions and those close to them. Early intervention and treatment greatly improve the likelihood of recovery.

Anyone who suspects they or a loved one may have an eating disorder can contact the National Alliance for Eating Disorders, which offers a daytime helpline staffed by licensed therapists and an online search tool for treatment options.

For general mental health support at any time, people can call the Substance Abuse and Mental Health Services Administration 24 hours a day at 1-800-662-4357 (or 1-800-487-4889 for TTY).

Many other resources are also available, including:

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The term calorie describes the amount of energy in foods or drinks. The human body requires this energy to fuel essential metabolic processes.

The number of calories an individual needs each day varies based on biological sex, height, weight, activity level, and genetics. According to the Dietary Guidelines for Americans 2020–2025, the average female adult needs about 1,800–2,400 calories daily, while the average male adult needs about 2,400–3,200 calories.

To follow a 1,000 calorie diet plan safely, a person needs to eat lots of low-calorie but nutrient-dense foods. This helps reduce the risk of nutrient deficiencies while also reducing the chances of hunger pangs.

The key to a healthy, successful diet is to include lots of fruits and vegetables and include lean protein sources. These options are nutrient-dense and can help someone feel full. Some examples of low-calorie, nutrient-dense foods are:

Learn more about nutrition and why it is important here.

Some foods are very high in calories, and consuming too many of these types of food may mean that a person takes in more calories than they need.

High calorie foods to avoid or limit when aiming to achieve a moderate weight include:

Learn how processed foods affect health here.

Being in calorie deficit aids weight loss. A calorie deficit means using up more calories than you intake. However, research has not identified the optimal deficit, and it likely depends on the individual.

According to a 2018 article, people can often achieve weight loss safely and sustainably by decreasing their daily calorie intake by about 500 a day.

Although some diet plans may recommend consuming 1,000 calories a day or less as an effective tool for weight loss, it is not safe and is an unsustainable way to try and lose weight.

Some evidence shows that these diets can promote weight loss. An older study of 125 females with obesity involved the participants consuming either 1,000 calories or 1,500 calories daily for a year. The people assigned to the 1,000 calorie diet lost more weight than the 1,500 calorie group.

However, other studies show that while consuming 1,000 calories a day may result in significant weight loss, most people cannot sustain it and often experience significant weight regain. The reasons include regaining lost muscle mass and increased appetite.

Also worth noting is that the human body can adapt. Significantly decreasing caloric intake causes the body to decrease the energy it burns. Typically, when individuals increase their calorie intake, they regain the lost weight. They may even gain more weight because they are in a caloric surplus, which means they eat more calories than their body needs to function.

People who want to reduce calories to lose weight should do so in small increments and avoid drastic changes.

Learn more about the risks of losing weight quickly here.

Extreme reductions in calorie intake can cause harmful side effects, such as:

These diets can also change specific metabolic pathways inside the body. For example, they can change hormones such as ghrelin and cortisol, which play a role in feelings of hunger.

They can also decrease muscle mass and affect the number of calories the body uses each day. This increases the risk for weight regain once an individual no longer maintains the diet.

Learn how to cut calories and maintain muscle mass here.

The best way to lose weight safely and successfully is by adopting healthy eating habits.

Start with small, realistic goals, and then, as these become a habit, increase the goals. For example, make it a goal to start each dinner with a side salad or serve vegetables as a side dish. Once this becomes standard practice, introduce a second goal, such as having fruit with breakfast.

Also, think about setting some exercise goals. A good example is setting a goal to walk for 15 minutes 3 times a week. Once this becomes routine, increase the time or number of sessions each week.

Setting small goals and increasing them over time sets people up for success. Also, small goals are easy to implement and sustain.

Remember that it takes time to gain weight, so it may take even more time to lose weight safely. Quick weight-loss plans have little scientific support and can lead to individuals regaining all the weight they lost and more.

Learn how to lose weight successfully here.

A 1,000 calorie diet is a risky strategy for losing weight. While someone can safely follow the diet short-term, experts do not recommend that people follow extreme diets for extended periods because they can damage a person’s health and cause them to regain the weight they lost and more.

The safest way to lose weight and maintain weight loss long term is to develop and maintain small healthy habits and lose weight slowly.