If you listen to the many fitness gurus online, you’ve probably heard “calories in versus calories out” as the only way to lose weight.

While the saying holds some merit, it doesn’t fully explain the most healthy and effective approaches that will lead to sustainable, long-term weight loss.

As a result, many people have resorted to starving themselves of calories, which may be incredibly harmful to health.

In this article, you’ll learn why starving yourself isn’t a good idea for weight loss and how to implement healthier weight loss strategies.

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If you’re not familiar with the term, you may think intermittent fasting is the same as starving. However, when done properly, intermittent fasting can be a healthy and sustainable practice (1, 2).

Intermittent fasting is an eating pattern that involves cycling between “eating” and “fasting” periods. For example, the most typical form is 16:8, which involves an 8-hour eating window and 16 hours of fasting (1, 2, 3).

While intermittent fasting can help you lose weight, the goal is not to over-restrict calories. Rather, you simply eat your normal daily calories or a small calorie deficit in a shorter time frame each day (1, 2, 3).

On the contrary, starvation is usually defined as an extended period of time without food or with very limited food intake significantly below your body’s daily calorie needs. This leaves your body in a large calorie deficit and will lead to unsustainable weight loss.

Generally, nutritionists define a very low calorie diet as consuming 450–800 calories or fewer per day, which isn’t healthy or sustainable in the long term. As such, starving your body of calories may pose numerous health risks and is not recommended (4, 5, 6).

Summary

Intermittent fasting is defined as eating food within a specific time frame, while starvation involves withholding food completely or eating very few calories over an extended period.

To lose weight, your body needs to be in a calorie deficit, which includes expending more calories through exercise and/or consuming fewer calories from food. However, a larger calorie deficit doesn’t always mean you’ll lose weight and keep it off.

Though you may experience significant weight loss in the beginning, you may find it difficult to sustain this weight loss in the long term.

Even more problematic, if you starve yourself, your body’s survival mechanisms may adapt to stark calorie deficits. This may interfere with your intended weight loss plan in the first place.

Your metabolism slows down

During long-term calorie deprivation, your body begins to use its fat stores as a primary energy source and muscle and skeletal tissue as secondary energy sources.

Over time, your body responds to calorie deprivation by reducing your resting metabolic rate (RMR) via adaptive thermogenesis (metabolic adaptation). This makes your body less effective at burning calories in an effort to preserve as much energy as possible (7, 8, 9).

This was shown in a landmark study on 14 participants from the show “The Biggest Loser.” Over the 30-week show, participants lost an average of 129 pounds (58.3 kg) and their RMR dropped from an average of 2,607 calories per day to 1,996 calories per day (10).

Although they regained an average of 90 pounds (41 kg), their average RMR remained suppressed (1,903 calories per day) (10).

These results suggest they would need to consume fewer calories and expend more calories to maintain their weight, so it would be more difficult to sustain weight loss (10).

Yet recent studies suggest metabolic adaptation subsides if you’re no longer in a calorie deficit. It’s thought that most weight regain is due to excessive calorie intake, which may be due to increased hunger and feeling “free” from calorie deprivation (11, 12, 13, 14, 15).

Further, a slowed metabolic rate may fatigue you more easily. This is a strategic mechanism your body puts in place to prevent you from expending too much energy. Your body also increases the release of hunger hormones to motivate you to eat (9, 16, 17, 18).

Ultimately, your body will work hard to prevent further weight loss by slowing down your metabolism, especially during times of prolonged starvation.

Your body works less effectively

Depending on the severity of starvation, the number of calories restricted, and length of time, your body may begin to prioritize essential bodily functions, such as breathing and heart rate, and slow down nonessential bodily processes, such as (16, 17, 18):

  • Hair and nail growth. Your hair and nails may become brittle.
  • Immunity. Your immune system may have a harder time fighting infection and illness.
  • Digestion and hunger regulation. You may experience irregular or intensified hunger, recurring bloating, or stomach discomfort.
  • Reproductive health. Your menstrual cycle may change or stop.
  • Skin health. You may experience improper or delayed wound healing or premature aging.
  • Bone health. Your bones may become weakened.

Starvation puts your body in an unhealthy state that it desperately wants to get out of. Though at first you may lose weight quickly, your body needs enough calories to function properly and will work hard to restore your weight and health as quickly as possible.

May harm your mental health

Starvation and other harmful dieting behaviors can be detrimental to mental well-being.

Dieting through starvation may lead to the development of disordered eating behaviors such as food restriction, fear surrounding food choices, a negative relationship with food, excessive exercising, and an obsession with body weight and size (19, 20, 21, 22).

In severe cases, prolonged starvation can develop into an eating disorder such as anorexia nervosa, bulimia nervosa, or binge eating disorder.

If you believe you are beginning to develop an eating disorder or disordered eating patterns, it’s important to speak with a healthcare professional who can refer you to a specialist. You can also contact the National Eating Disorders Association Helpline for support.

Summary

Starving your body of calories is not healthy or sustainable. Over time, it may decrease your metabolism, cause your body to function less effectively, and lead to disordered eating behaviors.

Instead of putting your health at risk in the name of weight loss, you’re better off adopting healthy, sustainable habits.

Here are some science-backed ways to help you lose weight and keep it off (23, 24, 25, 26, 27, 28, 29):

  • Aim for a small calorie deficit. Most research suggests a 10–20% deficit is sustainable and manageable. For example, if your maintenance calories are 2,500 calories per day, aim for a deficit of 250–500 calories per day through a healthy diet and exercise.
  • Increase physical activity. Aim for a combination of strength training and cardiorespiratory exercise (running, walking, etc.) for at least 200 minutes per week, or about 30 minutes each day.
  • Add strength training to your routine. Strength training helps preserve and build muscle tissue during weight loss. Building more muscle mass can increase your metabolism.
  • Limit processed foods. Try to make most of your meals from whole, minimally processed foods, which are usually lower in calories and higher in protein, fiber, and healthy fats to promote fullness.
  • Eat more protein. A high protein diet can help preserve muscle tissue during a calorie deficit.
  • Drink mostly water. Limit sugary beverages, energy drinks, and specialty drinks, which tend to be high in sugar and calories. Instead, opt for water, flavored water, coffee, and tea most often.
  • Go slow. Most research shows that a sustainable and healthy rate of weight loss is around 1–2 pounds (0.45–0.9 kg) per week. Therefore, slowly add new healthy habits to help you stick to your weight loss goals.

The best diets are affordable, enjoyable, and sustainable. Remember that not all weight loss is healthy. Focus on adopting healthy lifestyle behaviors that make you feel energetic and that you enjoy doing.

Summary

Starving yourself in the name of weight loss isn’t healthy or sustainable. Healthy, sustainable weight loss is around 1–2 pounds (0.45–0.9 kg) per week and involves eating a nutritious diet and exercising regularly to reach a small calorie deficit.

Starving yourself in the name of weight loss isn’t healthy or sustainable.

While it may be tempting to deprive yourself of food, your body will suffer. After prolonged starvation, your body’s metabolism may slow down, your body may not function properly, and your mental health may decline. Though you may lose weight initially, you’ll likely gain it back.

If you’re struggling with establishing healthy eating habits or find yourself developing concerning eating behaviors, work with a health professional who can help you live at your healthiest.