Premier Private Personal Trainer & Online Coach

What Happens If I Eat 700 Calories A Day?

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

what happens if i eat 700 calories a day

If you’ve asked the question, “what happens if I eat 700 calories a day?”, that makes me believe one thing.

You want to lose weight.  And you want to lose it fast.  Dang it, that was two things.

Am I right though?

Thought so.

I want to explain to you what happens when you eat 700 calories a day for weight loss, both in the short term and break down the long term issues you might experience.

Short term effects of 700 calories a day for weight loss

Quick weight loss

If you truly stick to a low calorie count of 700 calories, it’s pretty much a given that the weight will start falling off your body.

Maybe you’ve thought about eating 700 calories in a day to lose weight quickly. It should be as simple as:

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

Seems simple right?  Follow the 3 phases and get results.  Unfortunately, there are lots of things missing in there. 

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

Before we move onto on the negative aspects of eating 700 calories a day, I have something very important for you to keep in mind.

If you are questioning what happens if you eat 700 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.

Less strength and a slower metabolism because of losing muscle

If you eat 700 calories to lose weight, we already know what happens right away.  You’ll lose weight.

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

That’s because when you drastically cut your calories, you’re not only going to lose fat.  You’re going to lose valuable muscle that your body wants.

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 of food as before to maintain your weight, which will in turn make it harder to lose weight in the future.

Diet flexibility is out the window

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 700 calories for weight loss?

  • Can you go out with friends for a couple mimosas at brunch? Nope.
  • What about having a slice of pie on Christmas? That’s out of the question.
  • Pizza and pasta with your significant other? No way Jose.


Check out my client Kimberly who kept flexibility in her diet and didn’t overly restrict her diet.  She stuck to a steady weight loss of around 1 pound per week eating 1400 - 1500 calories and still enjoyed the occasionally Ben & Jerry’s pint.

Imagine eating a pint of Ben & Jerry’s on 700 calories!  A whole pint is more than that!

what happens if i eat 700 calories a day

What happens if I eat 700 calories a day? Long term effects

Sluggish, irritable, and no energy

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 more than calories.  They need micronutrients (vitamins and minerals), and with such a low calorie restriction you are going to struggle to get those valuable nutrients into your diet.

Without those calories and micronutrients you might start feeling sluggish, irritable, 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.


Nonexistent 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.

Loss of hair and possible menstrual cycle issues

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 700 calories a day? 

Let’s go back to what I just spoke about with micronutrients, aka those important vitamins and minerals your body needs.  Not getting those essential nutrients your body needs puts you at risk of having some form of hair loss.


High chance of gaining it back

Let’s bring it back to one of my favorite TV show back in the day before I was a personal trainer.

The Biggest Loser!  Remember that show?

For those that don’t, the 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 making rapid weight loss seems normal without telling us what is really going on.

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.”

Can you imagine having 800 calories a day to MAINTAIN your weight?!  That is insane and definitely a place you don’t want to be!

Not only are these 700 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 eating 700 calories a day

Is 700 calories a day healthy?

For most people, 700 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 700 calories a day?

It’s going to be very hard to maintain 700 calories a day while getting enough nutrients you need.

For reference, 1 gram of fat is 9 calories, while 1 gram of carbs and protein is only 4 calories.   

Let’s take a scoop of peanut butter for example.

Peanut butter has a serving size of 2 tablespoons.  For those two small tablespoons, it’s 190 calories!  Can you believe that!  2 tablespoons of peanut butter and you’re already over 25% of your calories.

If you are going to eat 700 calories a day, it has to be mainly protein and vegetables.  Again, I advice you to not try it.

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:

How To Calculate Your Macros For Weight Loss

Fat Loss Meal Plan For Women

Fat Loss Meal Plan For Men

weight loss 700 calories a day

If I eat 700 calories a day, how much weight will I lose in a month?

A very healthy rate of weight loss is roughly 0.5 - 2 pounds a week at a moderate calorie deficit.  If you were to eat 700 calories, you could expect to double that or more.

But at what cost?

You’ve now learned that you won’t just lose fat, you’re going to lose muscle as well.  Additionally, you have all the other negative side effects that I talked about above.

If you are convinced you need to eat 700 calories a day for weight loss, I would recommend talking to you doctor.

Recap of what happens if you eat 700 calories a day for weight loss

Weight loss at 700 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 700 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.