Is a 500 Calorie Diet Safe?

500 Calorie Diet

Is a 500 calorie diet safe under any circumstance?

Crash diets containing as little as 500 calories have been around for decades. In fact, chances are most people who diet regularly have tried one of these diets at some point in their lives.

But are they safe? And how exactly do they affect your metabolism and your health when you use them, especially if it’s for more than just a few days?

The surprising answer is that, under controlled conditions, very low-calorie diets (VLCD) can be very useful. However, they are not for everybody and they should not be attempted without proper guidance from a professional, such as a doctor or a dietitian.

The average person needs a minimum of 1,200 to 1,500 calories a day to maintain normal bodily functions. The exact amount depends on age, current weight, and gender (men usually require more calories than women).

Cutting down your calorie intake to anything lower than that is sure to result in weight loss – but it might come with consequences. This is especially true for crash diets that rely on a single food (such as the Cabbage Soup Diet) or that eliminate an entire food group, as it’s the case with low-carb diets.

Fad Diets and Very Low Calorie Intake

Many of the well-known diets out there are actually very low-calorie diets. This is the case of the grapefruit or Hollywood diet, for example, as well as the HCG Diet and the Sacred Heart Diet.

According to WebMD, any diet that recommends a daily intake of 800 calories or less is considered very low in calories and should only be used in very specific cases and only for short periods of time.

The main problem with VLCD is that these are diets that don’t teach you anything about healthy eating and changing bad habits. Even worse, most of these diets do not lead to permanent weight loss: once you’re back to eating normally, you are very likely to regain everything you’ve lost.

In the case of crash diets that also eliminate carbohydrates, simply drinking, eating salty foods or adding back some carbs (including healthy ones such as carrots and other starchy vegetables) might be enough to get you back to your original, pre-dieting weight.

Dangers of a 500-Calorie Diet

For the average dieter, 500 calories is simply not enough to provide well-rounded nutrition. Some food groups, including dairy and grains, are too high in calories to be allowed in a 500-calorie diet. As a result, you’ll have to exclude them and miss out on important nutrients such as calcium, B vitamins, and fiber. Lack of iron and vitamin B12 might lead to anemia if you continue on a VLCD for a long period of time.

Other common problems associated with very-low calorie diets include fatigue, nausea, vomiting, dizziness, and constipation. In addition, the Weight Control Information Network points out a significant number of people on a VLCD will develop gallstones as a result of the rapid weight loss.

Perhaps the major drawback of a very low calorie diet is that these diets are uniform, meaning they’re not usually adapted to each individual but are instead a one-size-fits-all solution to those looking for a quick fix. The problem with this, however, is that the amount of calories and nutrients needed by a woman needing to lose 10 lbs. are definitely not the same as those needed by a 300-lb. men trying to lose 70 lbs. Without professional guidance to understand unique situation and needs, chances are dieters will end up causing more harm than good with a VLCD.

Who Should Try It

People with a BMI of 30 or more are considered obese and are at an increased risk for a number of health issues, including high blood pressure, diabetes, and high cholesterol. For them, losing weight fast can be life saving, so a very low calorie diet simply makes sense.

In a study published in Diabetes Care, the journal of the American Diabetes Association, experts pointed out that, when compared to traditional weight loss methods, VLCDs are highly effective for obese non-insulin-dependent  patients trying to lose weight. In addition, because the initial weight loss is very fast, VLCDs are extremely useful in cases where a significant loss is needed to avoid medication or to prepare for surgery.

The study does point out that diets containing 500-800 calories can be risky, but when used in a medical setting and properly managed, the benefits greatly outweigh the risks.

However, it’s important to keep in mind that these diets should not be attempted privately. In an article published on the Journal of the American Dietetic Association, experts pointed out that, when using a VLCD, “careful monitoring by a physician experienced in such programs and by a registered dietitian is essential.”

In fact, the article emphasizes the importance of a multidisciplinary team approach when cutting down calories to such a small amount. This is to ensure not only the safety of the program, but also to make sure the patient learns about the changes being introduced and can benefit from them.

In addition, people undertaking a VLCD should be at least 30 percent overweight, clear of certain medical conditions (such as for liver or heart disease), and committed not only to the diet itself but also the maintenance period that comes after it. Before getting started, dieters often have to undergo a series of tests to confirm that they are relatively healthy and free of chronic diseases such as diabetes, heart conditions, and high cholesterol.

If the tests reveal that one or more of these conditions are present, doctors might need to reevaluate the type of VLCD to be used. Diabetics in particular must be carefully monitored, as cutting down calories or eliminating certain food groups can have a serious impact on blood sugar levels.

In short: a very low-calorie diet is not meant to provide a quick answer to weight loss, but to help those that need a change due to health reasons.


Journal of the American Dietetic Association: Position of the American Dietetic Association: very-low-calorie weight loss diets
Weight Control Information Network: Very Low-Calorie Diets
WebMD: Very Low-Calorie Diets: Everything You Need to Know
NHS: Very Low Calorie Diets
Diabetes Care

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