Diets such as the 500-calorie diet are called very-low-calorie diets (VLCD). Although doctors have prescribed VLCDs for many years to treat some conditions, eating so little comes with risks.
VLCDs may also be useful before bariatric and laparoscopic surgery. Losing fat can reduce operative time, blood loss, and the risk of complications.
However, while eating 500 calories per day may help a person lose weight, it is not a suitable or safe diet for everyone and comes with certain health risks.
People should consider the following risks before following a 500-calorie diet without a doctor’s supervision:
1. Chance of nutritional deficiencies
Certain groups of people may be at higher risk. Older adults, in particular, may be at risk as they are more likely to have reduced nutrient absorption from the small intestine.
2. Possibility of gallstones
Gallstones form in the gallbladder. They can block the bile duct and cause abdominal pain. The following factors can also increase a person’s risk of gallstones:
- fasting for extended periods
- obesity
- pre-existing gallstones
- repeatedly losing and gaining weight
A gradual weight loss plan involving a balanced diet with plenty of fresh vegetables and fruits may help to prevent gallstones.
3. Lack of healthful fats
Of the three macronutrients fat, protein, and carbohydrates, fat is the highest in calories.
Because fats contain more calories, it is difficult to eat enough of them on a 500-calorie diet. Unsaturated fats, such as those in salmon and avocado, offer certain health benefits to the body when someone eats them in moderation.
A low fat diet also increases the risk of deficiencies of fat-soluble vitamins, such as vitamin E, and poor absorption of antioxidants.
4. Meal replacements are not a long-term solution
People sometimes use meal replacements for one or two of their daily meals while on a low calorie diet. A meal replacement is usually a liquid alternative, such as a shake or juice, that someone consumes instead of a solid meal.
Although these can be useful, consuming them for a prolonged period can harm a person’s health.
Vitamins, minerals, macronutrients, and phytochemicals from whole foods all have important interactions in the body. Artificial meals cannot replace these vital interactions.
5. It can be costly
Even though someone on the 500-calorie diet is eating less, the cost per pound of food can be higher than on other diets.
The cost of meal replacement foods, such as SlimFast, can be much more than the equivalent amount of whole foods.
6. Lifestyle changes vs. a quick fix
People aiming to lose weight from a VLCD may not implement other weight-loss strategies, such as nutrition counseling and physical activity.
Being on a VLCD does not establish good health behaviors, as the diet is not sustainable over time and people may find it challenging to stick to long-term.
People may see longer-lasting weight changes if they aim for slower, consistent weight loss that involves a balanced diet and regular exercise.
7. Muscle loss
A 2023 review suggests that loss of muscle mass is the main risk of a VLCD. To minimize this risk, the researchers suggest that people should:
- eat enough protein
- work with a healthcare professional
- maintain muscle with a resistance exercise training plan
8. Missing out on social events
Eating out can be difficult on a 500-calorie diet. Some restaurants do not reveal the total calorie count of their meals, and meals in restaurants may have higher calorie counts than those a person makes at home.
Being on the 500-calorie diet may also cause anxiety about ordering food or eating with family and friends.
9. Unsuitable for people with certain health conditions
According to a 2018 article, people with the following health conditions should not try a VLCD:
People should consult a doctor before starting a 500-calorie diet to ensure it is a safe option for them.
10. Possible decrease in bone health
The long-term effects of a VLCD on bone health are unknown because people do not typically use the diet for prolonged periods.
However, a lack of essential minerals and nutrients may weaken bones over time.