What Happens When You Lose Too Much Weight Too Fast?

by James Porterson about a year ago in weight loss

When people try to lose weight, they want instant results. Gaining it all back is just one of the reasons it's not a good idea to lose too much weight too fast.

What Happens When You Lose Too Much Weight Too Fast?

When you attempt to lose too much weight too quickly, you burn fat and muscle. When you burn muscle, you slow down your metabolism. This makes it harder to burn fat at rest. Long term it is not a good idea to lose too much weight too fast.

Stomach Discomfort

You look in the mirror one day, or see a picture of yourself, and realize that you’ve put on too much body weight. You want to lose weight right now, so you begin crash dieting, dramatically limiting the amounts of food you’re eating hoping for fast weight loss in a short period of time. The problem is that you intestines don’t understand what you’re up to. It’s a shock to your system and it takes time for your insides to adjust, this can result in constipation or diarrhea, or bouts of both. It's certainly not the way to encourage your friend to lose weight. It is much better to have a goal of healthy weight loss by with a target of losing a maximum of two pounds per week. This type of weight management is much healthier long term.


Headaches are another side effect of rapid weight loss. When you lose weight too quickly, your metabolism changes. You begin to deplete glycogen, causing adrenaline and insulin fluctuations, starving your brain over a short period, resulting in headaches and mood swings. The amount of weight you lose in a short time dictates if this type of diet is puts you at risk. If you’re losing three or more pounds per week, you’re losing too much weight too fast. It’s not worth the risks of losing your health. Instead of trying to lose weight quickly, go for a slower burn. You will keep the weight off longer and you will be healthier, and isn’t that really what you want in the end... a healthier body.

Mood Swings

Mood swings are a result in hormonal changes caused by losing wight too quickly. If you do crash dieting like starving yourself twice a week, your body burns too much glycogen, causing your hormones to fluctuate. Similar to what happens during a female’s menstrual cycle, the shifting hormones causes depression, fatigue, anger, and irritation. Rapid weight loss can throw your hormones out of whack, which puts you at risk for a whole host of other problems. While it is normal to want instant gratification, damaging your health is not worth the weight you’re losing. Proper weight management is the key to healthy weight loss. Remember that it’s not all about body weight; it’s about your fat to muscle ratio. Two people can weight 120 pounds and look entirely different, with one having more fat to muscle and the other having more muscle to fat.

Sleep Disturbance

One of the other risks of losing too much weight too fast is sleep disturbance. Stress hormones insulin, cortisol, and adrenaline fluctuate, your sleep-wake cycle is dramatically disturbed by fast weight loss over a short period of time. The number of pounds per week lost and the total amount of weight lost are not just related to the amounts of food you are eating, but what you are eating. If you are only eating carrots, celery, and salad, you are not getting enough protein to prevent muscle wasting, and you are not eating enough carbohydrates to sustain energy. Fast weight loss doesn’t just burn fat—it burns into your muscle and those with smaller muscle mass have a slower metabolism. Therefore, those who lose weight quickly suffer from a slower metabolism over the long term.


Other risks of losing weight too quickly include dizziness. Losing more than two pounds per week by limiting the amounts of food you eat too drastically puts you at risk of having fainting spells or falling over from being dizzy. This is caused by hormonal shifts, blood pressure changes, and equilibrium disturbances all caused by rapid weight loss. Crash dieting for a short period of time is really just an unhealthy quick fix where healthy weight loss and weight management is a lifestyle change that lasts long term. Don’t become too consumed with the amount of weight you’re losing instead of looking at the big picture. It’s how your clothes fit you, how you look in your own skin.

Decreased Energy

When attempting fast weight loss, consider that muscle weighs more than fat. If you embark on a healthy diet and exercise regime that includes weight training, you may not lose body weight, but you will have a healthier body mass index. If you just crash diet and do endless cardio workouts, you will lose weight quickly, and that puts you at risk of losing too much weight. While that may sound good at first, the mood swings and decreased energy won’t be worth it. You need to eat properly in order to lose weight. When your body is is starved for food, especially when limiting carbohydrates, your energy is severely decreased. You end up feeling too tired to work out, which can be detrimental to your new health goals. Instead, make sure to eat healthy carbohydrates that provide a slow release of energy.


Anemia is one of the risks of losing too much weight over a short period of time. Crash dieting limits the amounts of food you consume which can deplete you of the nutrients you need to sustain a healthy body. Losing weight too quickly puts you at risk of becoming deficient in iron resulting in anemia. If you’re losing 3 or more pounds per week of body weight, you are setting your body up to experience unhealthy side effects. To avoid these problems, make sure you are on a healthy weight management program for the long term. Your health too important to take chances with, and while carrying around an extra amount of weight is unhealthy, shocking your system by withholding food is just as bad.

Brittle Hair

If you’re experiencing brittle hair after you lose too much weight too fast, you are depleting your body of necessary nutrients. Rapid weight loss usually occurs when people limit the amount of fats they eat, this can have serious health consequences. The body needs healthy fats to function. It not only affects your hair, but every organ in your body. When you cut all fats to lose weight quickly, everything dries up. Instead, eat healthy fats like olive oil, avocados, nuts, seeds, flax seeds, and coconut oil. Use these fats as substitutes for butter and saturated fats for healthy weight loss. This will help you avoid a plethora of problems from mood swings to brittle hair. Remember that the goal is to get healthy and look healthy, and fast weight loss is not the way to do it.

Dry Skin

Dry skin is another side effect of cutting fats too quickly while on a rapid weight loss program. Your skin will become dry and wrinkled, and when your losing a significant amount of weight too fast it can cause that skin to sag because there is no elasticity. Instead of just cutting the amounts of food you eat, change the foods you eat. This is a sure path to healthy weight loss, where instead of losing body weight you are losing fat. The idea is to become strong and healthy, not weak and frail. Keep that in mind long term.

Muscle Wasting

Crash dieting can result in muscle wasting. Muscle needs protein to sustain itself and build. As we age, we lose a percentage of muscle each year, which results in our metabolism becoming slower. If you add fast weight loss to that equation, you lose even more muscle each year. The risks of losing that much muscle include weakened support for bones and organs. If you lose too much weight too fast, it puts a burden on the entire body as it begins to waste away a long with the fat you are burning. What most people don’t understand is that dieting doesn’t just burn fat and you cannot target the areas from where you will lose fat. You may gain fat unevenly, but you will always lose it evenly.

weight loss
James Porterson
James Porterson
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James Porterson

Former obese teen turned nutritionist. Enjoys writing about staying active and proper nutrition.

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