A very low calorie diet is a clinically supervised diet plan that involves eating about 800 calories a day or fewer. They are sometimes considered for obese and severely obese people who are managing diabetes, going to have surgery or preparing for fertility treatment.
Some people go on a very low-calorie diet for rapid weight loss, often consuming only 800 calories a day. This type of diet usually includes special foods such as shakes, bars, or soups to replace meals and for added vitamins. Very low-calorie diets can help a person achieve weight loss of up to 3 to 5 pounds per week.
In addition, consuming as few as 800 calories daily may not give you the energy you need for daily living and regular physical activity, especially if you eat the same foods every day. Talk to your doctor or dietitian to make sure you get the nutrients you need while on a very low-calorie diet.
Is the Fast 800 diet safe to follow in the long term? The NHS suggest that should you choose to follow a VLCD you should do so for no longer than 12 weeks and under the guidance of a suitably qualified healthcare professional.
According to founder Dr Michael Mosley (opens in new tab), those who closely follow the Fast 800 plan could see themselves lose up to 11lb in two weeks by limiting their daily intake to 800 calories a day.
However, calorie intake should not fall below 1,200 a day in women or 1,500 a day in men, except under the supervision of a health professional. Eating too few calories can endanger your health by depriving you of needed nutrients.
As a general rule, people need a minimum of 1,200 calories daily to stay healthy. People who have a strenuous fitness routine or perform many daily activities need more calories. If you have reduced your calorie intake below 1,200 calories a day, you could be hurting your body in addition to your weight-loss plans.
Generally, the recommended daily calorie intake is 2,000 calories a day for women and 2,500 for men.
Calories and Your Health
But if your calorie intake dips too low, says Lummus, your body could go into starvation mode. "Your body will start to store fat because it thinks it is not going to get anything," says Lummus. "You will be at a point where your body is kind of at a standstill."
On a typical 800 calorie day, followers can consume an egg on toast, a milk coffee, a salad with tuna and a small, 300 calorie dinner of 100g of protein and vegetables. This is generally far too little food for the average person, doing some moderate activity each day.
When you eat too few calories, e.g., a 900-calorie diet, it interrupts your metabolism. As stated above, your body thinks that you are starving, and thus, it signifies to your appetite hormones that something is wrong. They slow down your metabolism, which means that you will no longer be burning calories.
A 500-calorie diet is an extreme form of a very low-calorie diet (VLCD). It requires you to drastically reduce the amount of food you eat, usually to a maximum of 800 calories per day. VLCDs use meal replacements like drinks, shakes, and prepared food bars instead of meals for at least two meals a day.
Restricting intake to fewer than 1,000 calories daily can slow down your metabolic rate and lead to fatigue since you're not taking in enough calories to support the basic functions that keep you alive.
What is Rapid Weight Loss? The maximum amount of weight you can lose in one month is about 20 pounds, or 5 pounds per week. But to achieve this goal you'll likely have to eat just 500-800 calories daily for 30 days vs. 1,200-1,800 calories often recommended during a 1-2 pound per week weight loss.
People may turn to 1,000 calorie diets when they are desperate to lose weight quickly, such as before a vacation. While adults could follow this type of diet relatively safely for a couple of weeks, it is not something that doctors advise for extended periods.
Unintentional weight gain occurs when you put on weight without increasing your consumption of food or liquid and without decreasing your activity. This occurs when you're not trying to gain weight. It's often due to fluid retention, abnormal growths, constipation, or pregnancy.
Typical signs that you're not eating enough can include losing weight, feeling tired, getting ill more often, hair loss, or skin problems. In time, menstrual irregularities and depression may occur. Children may not grow as expected.
It is commonly said that if you eat too few calories, your metabolism will slow down to a point where you no longer lose weight. Part of this is true: as you lose weight your energy expenditure does drop. However, consuming too few calories cannot and will not cause you to gain weight. This is simply impossible.
According to dietary guidelines in the United States, adults 21 years old and older should consume anywhere between 1,600 and 3,000 calories per day.
Though it differs depending on age and activity level, adult males generally require 2,000-3000 calories per day to maintain weight while adult females need around 1,600-2,400 according to the U.S Department of Health.
Starvation can include deficiencies in minerals, protein and the fats which our brain uses to function properly. Most of us get our needs met over time, we don't have to eat a perfect diet every day because much of what sustains us is held in reserve. But the stores can run dry in just a few days.
When a person has been eating a low-calorie diet for long enough to actually be starving—there's no specific caloric threshold or length of time for this to happen because it's so individual, the experts explain, but it certainly takes longer than a day without food—a few physiological processes take place.
Undereating may cause weight gain for some people, but even if it doesn't, it's important not to eat so little that it adversely affects your health. From constipation to immune dysfunction, not eating enough can lead to a host of health issues.
Is The 800-Calorie Diet Safe? No, it is not. As a general rule, men and women require about 2500 and 2000 calories, respectively, to maintain weight. You should note that this is not a standard number as your recommended daily caloric intake is determined by weight, ages, height and level of physical activity(23).