Very low calorie diets, or VLCDs, have been around for decades. Millions of teenagers, young women, and men starve themselves to achieve fast weight loss. It's not unusual to see someone eating less than 500 calories a day. Unfortunately, this approach doesn’t work. If very low calorie diets were effective, everyone would be lean. Eating too few calories can actually affect your health and well-being, causing poor energy, slow metabolism, nutritional deficiencies, and osteoporosis.

What Are Very Low Calorie Diets?
This term describes any diet with extremely low calorie consumption, such as 500 or 800 calories a day. Most VLCDs consist of liquid meals, protein shakes, smoothies, and energy bars, and eliminate whole food groups. It's difficult to meet your daily nutrient requirements by eating 800 calories per day or less.

Very low calorie diets were initially prescribed to morbidly obese patients who needed to lose weight before bariatric surgery. They are not meant for the general population because of the risks involved. Yet, more and more people are switching to VLCDs to shed fat quickly.

Studies indicate that very low calorie diets cause serious health problems in the long run. They not only deplete your body of nutrients, but also slow your metabolism and facilitate gallstone formation. The lack of fiber affects digestion and triggers blood sugar spikes. These diets are low in protein, causing muscle loss. They also provide little or no carbs, which affects your energy and stamina.
Why Do Low Calorie Diets Fail?
VLCDs are anything but healthy. They may cause weight loss in the first few weeks or months, but their risks outweigh the benefits. In the long run, very low calorie diets reduce your metabolic rate, trigger plateaus, and affect immune function. This approach also increases the risk of chronic diseases, such as diabetes and metabolic syndrome.

The fewer calories you eat, the slower your metabolism. Your body has the ability to adapt to a low calorie intake. Additionally, eating too little triggers muscle loss and causes the body to enter starvation mode. As a result, you'll end up with a low body weight and decreased lean mass while your fat percentage will still be high. Very low calorie diets may also cause:

• Gallstones
• Kidney and liver failure
• Cardiovascular disease
• Metabolic disorders 
• Bone loss
• Increased risk of osteoporosis
• Poor immunity
• Amenorrhea in women
• Irregular menstrual periods
• Hormonal imbalances
• Low testosterone in men
• Reduced thyroid function
• Low energy 
• Slow digestion
• Constipation
• Anxiety and depression
• Poor brain function
• Insulin resistance
• Type II diabetes

A diet that's too low in calories also increases your risk of weight gain and binge eating. Many of those who embrace VLCDs are struggling with bulimia, anorexia, and other eating disorders. They also have a poor body image and experience mood swings, depression, and high stress levels. Research shows that very low calorie diets also affect the levels of leptin, ghrelin, and other hormones that influence satiety and hunger.

Health experts advise against any diet that eliminates entire food groups or requires extreme caloric restriction. Unless your body mass index is greater than 30, steer clear of any weight loss plan providing less than 1,200 calories a day. VLCDs are particularly dangerous for children, teenagers, and pregnant women.

The best way to shed stubborn fat is to tweak your diet and exercise routine in a slow, controlled manner. If you're already on a very low calorie diet, gradually increase your calorie intake. This will increase your metabolism and allow your body to recover from starvation.

Summary

• Very low calorie diets provide 800 calories per day or less. 
• In the long run, they may cause eating disorders, heart disease, diabetes, and bone loss. 
• VLCDs cause severe damage to your health and increase the risk of chronic diseases. 
• Most people regain the weight as soon as they return to their old eating habits. 
• Gradual weight loss is much safer and effective than VLCDs.