eating 600 calories a day

Eating 600 Calories A Day: A Good Idea?

There are all types of diets out there, most of them based on calorie restriction. One popular calorie restricting diet is the 600 calories per day diet. This can be beneficial for quick weight loss when done periodically. However, if you were to do this every day, you would end up in a state of malnutrition.

What is the 600 Calorie Diet

The 600 calories per day diet is a type of intermittent fasting. This is a popular and proven method of fat loss dieting that involves alternating between periods when you are fasting and periods when you are eating. The eating period is known as your eating window. 


One of the most popular forms of intermittent fasting is known as 16/8. This variation divides your 24 hour day into a 16 hour period of not eating and an 8-hour eating window. An example of how this might work is for a person to stop eating at 7 pm and then not eat until 11 am the next day. They then have the 8 hours between 11 am and 7 pm as their eating window. 

The 600 calorie diet is also called the 5:2 diet. It involves eating normally for 5 out of every 7 days. The other two days you fast. That doesn’t mean that you eat normally Monday through Friday and then fast on the weekend. The fasting and non-fasting days are staggered throughout the week. 

You can choose to follow a 16/8 protocol where you limit your eating window feeding to 600 calories. Or you can choose to eat at any time during the 24 hour period, so long as you do not exceed 600 calories in that time period. 

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Versions of the diet have women doing a 500 calorie diet while men follow a 600 calorie diet plan.

Is the 600 Calorie Diet Healthy?

The 600 calorie per day diet for weight loss can be safe so long as it is not done to excess. If it is limited to two days per week, it can be an effective diet regimen to lose weight. So long as you are eating a healthy, balanced diet on the other days of the week and meeting your daily calorie maintenance level, the two-day restriction will not cause you to lose muscle mass. 

Restricting your calorie intake to 600 calories in a day will have you at around 2000 calories lower than your daily calorie maintenance level. This will force your body to turn to its stored calories in the form of body fat to meet your energy needs for that day. As a result, you will lose fat. 

There are some people, however, who should not go on a 600 calorie diet. These include:

  • Those with low blood sugar levels
  • Children under the age of 18
  • Women who are pregnant or breastfeeding
  • People with an eating disorder
  • Diabetics
  • People who are on blood pressure medication

How Much Weight Can You Lose on a 600 Calorie Diet?

When it comes to weight loss on a diet such as the 600 calorie diet, you need to make the distinction between weight loss and fat loss. If you do it the wrong way you will lose lean muscle mass. Muscle loss is something you never want to do. So, your goal should be to lose weight safely by only losing stored body fat.

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After your 600 calories fast day, you may notice a weight loss of as much as 1 kg (2.2 lbs). However, when you eat normally the next day, you will put some of that weight back on. Your net fat loss for the day of fasting should be around half a kg or just over one pound.

That might not sound like very much, but if you are doing the 5:2 diet, you will lose about a kilo or 2.2 pounds per week. If you do that consistently you will lose around 9 pounds of fat per month or 45 pounds in a 6 month period.

Regular small amounts of weight loss are the key to losing weight and keeping it off. You should avoid drastic diets that promote fast weight loss. 

Will You Pig Out The Next Day?

You might think that if you were on a caloric intake of just 600 calories a day, you would rebound by eating a whole lot of extra calories the next day. But that’s not what the research indicates. 

 Dr. Krista Varady from the University of Illinois in Chicago conducted a study that put people on a strict calorie limit every other day.  Women were restricted to just 400-500 calories, while men were allowed 500-600 calories. The calories were all consumed at lunchtime. On an alternate day, they were allowed to eat whatever they wanted.

The study participants did not gorge themselves on an alternate day. They ate, on average, 110% of their energy requirements. Their results were similar to what would be obtained on a traditional diet.

Will You Have Low Energy?


On the face of it, it makes sense. We get energy from food. So, if we don’t eat, we’ll be dragging the chain all day long. As we’ve already discussed, however, your body has a lot of stored energy just waiting to be chewed up. It’s probably sitting around your belly area right now. Intermittent fasting provides the trigger to be able to access it so that you use fat for energy.

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Initially, there will be a transition period, where you will get a bit of a shock to your system. After all, you’re going from a lifetime of eating whenever you get the urge to only eat within a set window. Pretty quickly, though, your body will adapt. In a 2008 study which, was published in the American Journal of Clinical Nutrition, researchers studied the effect of fasting on cognition, activity, sleep, and interstitial glucose concentrations. They found that none of these factors were affected by short-term fasting.


The 600 calorie diet can be an effective and healthy weight loss method. If you keep your 600 calorie diet to just two days per week and keep at it consistently while eating a healthy diet on the other days, you can lose around 9 pounds per month. 

Frequently Asked Questions

What should I eat for lunch if I am a 600 calorie diet?

You may actually decide not to eat lunch, saving your calories for breakfast and dinner. In that case, you may want to just have a cup of black coffee. If you are going to have a lunch meal, have a decent portion of protein with a side of low glycemic carbs. You could have a  small portion of chicken (half your fist size) and brown rice. 

Steve Theunissen

Steve Theunissen is a former gym owner and personal trainer based in Tauranga, New Zealand. He is the author of six hardcopy books and more than a hundred ebooks on the topics of bodybuilding, fitness, and fat loss.

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