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8 risks to health in following a very low calorie diet

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If you want a better body, or want to lose a few inches, you may be consider going on a diet to cut calories. Depending on how many calories you cut out of your day, you may be simply reducing the size of your regular evening meal, or maybe skipping meals altogether.

But, when you start getting toward the more extreme side of low calorie diets, that is when you begin running into negative health effects instead of the benefits you may have expected.

The purpose of a low calorie diet

If somebody wants a guaranteed means of losing weight, they have to use a diet that allows them to create a negative energy balance. This energy “deficit” leads to weight loss because the body is burning more energy than it takes in or consuming.

Some diets, however, go further and call for far fewer calories than is normally recommended by health professionals.

Whilst such programmes might seem a quick way to weight loss, there are actually a number of health problems that they are risking by embarking on such diets, especially without taking medical advice first.

 What is a very low calorie diet?

The recommended estimate calorie needs of a normal man falls between 2,000 and 2,800, depending on activity level. For a woman, that estimate is between 1,600 and 2,400.

If your diet restricts your calorie intake to 800 calories a day or less, you are on a very low calorie diet (VLCD).

 What are the benefits of a low-calorie diet?

You are almost certain to lose weight if you place yourself on a low or very low calorie diet. In fact, you could lose around 3 to 5 pounds per week.

If you are suffering from obesity, diabetes, high blood pressure, or high cholesterol, this sort of diet could help you significantly in your fight against your ailments.

However, studies have shown that whilst such extreme diets are effective when it comes to initial weight loss, the long-term effects are not so positive because of the associated health risks.

Here are 8 potential health risks of a very low calorie diet.

1. Constipation

Constipation is simply the state of not having enough bowel movements. Because low calorie diets involve eating so little food overall, fewer carbohydrates especially, you are not likely to be consuming anywhere near the recommended daily value of fibre in your diet.

If you are suffering from constipation whilst on one of these diets, seek a fibre supplement, or substitute a fruit or vegetable for one with much greater fibre content.

2. Fatigue

Due to the long stretches of time you go without eating while on these extreme calorie reduction diets, your blood sugar drops. As a result, your energy drops as well.

This occurs because your body, including your brain, needs calories to function properly. When you cut them too low, it becomes harder to keep your focus.

Young woman with eye fatigue

3. Gallstones

One serious side effect of low calorie diets can be gallstones.

When you lose weight too quickly, your liver secretes extra cholesterol, leading to too much cholesterol in the bile, which can lead to these gallstones.

Gallstones can lead to:

  • Pain in the upper abdomen and back
  • Nausea
  • Vomiting
  • Bloating, indigestion, heartburn, and gas.

4. Headaches

Another side effect of unsafe, rapid weight loss is frequent headaches. As with fatigue, headaches can be caused by low blood sugar thanks to the lack of glucose in your bloodstream.

If you are experiencing headaches, drink lots of water before and after exercise and meals. If the headaches persist, then you need to increase your calories.

Headache Dizzy

5. Loss of Nutrients

With a low calorie diet, not only will you be limiting the amount of calories needs to function at a normal level, but you will also be depriving yourself of essential nutrients.

When you are on a low calorie or very low calorie diet, the only way you will get anywhere near the recommended amount of nutrients is to supplement carefully.

6. Menstrual Problems

For women, rapid loss of weight can force the female body to start shutting down all the non-essential survival functions. The menstrual cycle is one of these.

Whilst for some the idea of having lighter periods, or even none at all, might seem an attractive proposition, it unfortunately is, overall, unhealthy. Hormone levels are disrupted, as the body’s normal method of regulating these hormones has been shut down.

7. Muscle Loss

A study reported by WebMD demonstrated that in two groups, one on a low calorie and the other on a very low calorie diet, muscle loss was higher in those who consumed fewer calories.

A significant percentage of muscle loss was recorded in both groups, but much more so in the very low calorie diet group.

This is because the body begins to seek new means of acquiring energy, and starts to harvest the muscle tissue instead of its normal food source, glucose, in the blood.

8. Nausea

Because your body is not receiving enough nutrients, and very little in the way of carbohydrates and sodium, it is possible you may experience nausea.

At a certain point, you may even reach the point of having visual disturbances as a result of your weakened state. If this happens, you should immediately consult a doctor.


If you are looking for immediate weight loss or amelioration of the symptoms of obesity, diabetes, high blood pressure or cholesterol, then a very low calorie diet could be of some benefit.

However, if followed for any length of time, the associated health risks mean that such diets can cause more problems than they solve. Therefore, you need to make sure that you transition smoothly into a healthy diet afterward – one that will help you sustain long-term weight loss.

Above all, anybody considering embarking on a very low calorie diet should seek medical advice before they begin, to make sure that they are not placing their bodies under undue stress and strain by undertaking it.