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What Happens If I Eat 600 Calories A Day?

Is 600 Calories Enough? Learn The Good, The Bad, And The Ugly Truth

By: Zack Mathews, NASM - CPT, CES, PES, PN-L1

If you are pondering the question, “what happens if I eat 600 calories a day?”, that makes me believe you want to lose weight and you want to lose it fast.

Am I right?

Thought so.

Today I’m going to explain to you what happens when you eat 600 calories a day for weight loss in the short term and break down the long term issues you might experience down the road.

What happens if I eat 600 calories a day? Short term effects

Rapid weight loss

If you truly stick to a drastically low calorie count of 600 calories, it’s pretty much a given that the weight will start falling off your body.

Maybe you’ve thought about eating 600 calories in a day to lose weight quickly. It should be as simple as:

  • Step 1: Drastically reduce calories
  • Step 2: The weight falls off your body
  • Step 3: Your happy because you hit your goal quickly

Seems simple right?  Well, it’s not that easy my friend.  

Besides the quick weight loss, you aren’t going to see many benefits.

Before we move onto on the negative aspects of eating 600 calories a day, I have something very important for you to keep in mind.

If you are questioning what happens if you eat 600 calories a day, please speak with your doctor before starting a drastic drop in calories.  Work with them to see what is the best option for your current and long term health.  There is a chance that an obesity related disease will require a low calorie goal so always speak with your doctor first.

Muscle loss leading to less strength and slower metabolism


If you eat 600 calories to lose weight, we know you will lose weight. 

But did you realize I didn’t say lose fat?

That’s because when you drastically cut your calories, you will lose muscle as well as fat from your body.

This is something you don’t want to to happen.  Less muscle means less strength and even more important, a slower metabolism.

A slower metabolism means you won’t be able to eat the same amount as before to maintain your weight, which will in turn make it harder to lose weight in the future.

No diet flexibility

I understand that you want to get that weight off but I think it’s important to enjoy the journey while you’re on it.

You can still get great results AND enjoy your favorite foods from time to time.

What type of flexibility do you have if you are only eating 600 calories for weight loss?

  • Can you go out with friends for a couple drinks at happy hour? Nope.
  • What about having a slice of cake on your child’s birthday? That’s out of the question.
  • Pasta and wine with your significant other? No way Jose.


Check out my client Jacob who kept flexibility in his diet and still was able to lose a huge chunk of weight in 6 months.  

He did it by lifting weights, riding his bike daily, restricting his calories to an aggressive but appropriate level, and staying consistent.  He did this all while still having flexibility to have the occasional beer and pizza.

what happens If I eat 600 calories a day transformation
is 600 calories a day enough? client ate more and still lost

Eating 600 calories in a day - long term effects

Lower energy, irritable, and sluggish

An important question to consider is when do these long term effects come into play?  Depending on how much fat you have to lose, you’ll probably be able to get away with eating minimal to no calories (hence why some people can fast for an extended period of time). 

But at some point, and it’s different for all people, the negatives outweigh that initial positive weight loss.

The thing we can’t forget is that our bodies need micronutrients (vitamins and minerals), and with such a low calorie restriction you are going to miss out on many of those.

Without those calories and micronutrients you might start feeling irritable, sluggish, and have less energy than normal.

If you are constantly feeling like that when dieting, there’s a good chance your calories are too low.


Low sex drive

Just like too much fat on your body can affect your libido, the other extreme of drastic dieting can also play a negative role on it.

This study showed testosterone levels decreased and there was less sexual activity during a rapid weight loss phase.

Disruption in menstrual cycle and loss of hair

When a calorie deficit gets too extreme, there is a chance for females to have issues with their period and/or experience hair loss.

That’s a bad spot to be in and it’s not worth drastic weight loss for most people.

What happens with your hair if you eat 600 calories a day? 

Remember what I said in the last section about micronutrients?  Not getting those essential nutrients your body needs puts you at risk of having some form of hair loss.

High chance of gaining it all back

Remember the show “The Biggest Loser”?  

These contestants were fed extremely low calorie diets and exercised for hours on end to try and lose the most weight to win the grand prize.

The show did a great job of normalizing rapid weight loss without telling the whole picture.

According to an article from the Harvard Health Publishing,  “ One show contestant lost 239 pounds and achieved a weight of 191 pounds, yet six years later, after regaining 100 pounds of that lost weight, had to consume an 800-calorie-per-day diet to maintain his weight.”

Not only are these 600 calorie a day to lose weight diets putting you at risk of gaining it back but they also greatly affects your metabolism so it will be harder to maintain your new weight or try and lose additional weight.

Frequently asked questions regarding 600 calories a day weight loss

Is 600 calories a day healthy?

For most people, 600 calories a day is not enough nutrients to provide us the proper macro and micronutrients we need to live a healthy life.   For some extreme obesity related disease issues this might be a good option but it’s important to talk to your doctor before trying to eat this little of calories.

What can you eat on 600 calories a day?

It’s going to be very hard to maintain 600 calories a day while getting enough nutrients you need.

1 gram of protein is 4 calories, 1 gram of carbohydrates is 4 calories, and 1 gram of fat is 9 calories. With a few basic items you normally have daily, you’ll be past your calorie goal.

Check out the meal below.  It's a healthy meal with a balance of protein, carbs, fiber, and vegetables.  And it's 475 calories! That would almost be your whole calorie count for the day if you were trying to eat 600 calories a day to lose weight.

Instead, take a realistic approach and eat enough calories where you can lose weight and not feel miserable.  Check out these guides to help you out:

The Definitive Guide For The Best Macros For Weight Loss

Meal Plan For Female Weight Loss

Meal Plan For Male Weight Loss

Eat 600 calories in a day - unrealistic approach

Why am I not losing weight on 600 calories a day?

If you’re not losing weight on a drastically low amount of calories, there is a good chance that you are not tracking your food correctly.

You are either missing meals, snacks, bites of food, or you are not weighing your food and are instead guesstimating how much you are eating.

If you swear that you are doing everything right, I would recommend talking to you doctor.

What happens if I eat 600 calories a day? Recap

Weight loss at 600 calories is going to happen fast but the negative side effects will quickly take over.

Unless your doctor has advised you to be on a 600 calorie weight loss diet, I would recommend following a more realistic approach where you slowly lose weight, continue to get stronger, and don’t experience major side effects.