Calorie Restriction Side Effects – 7 Harmful Weight Loss Ways?


One of the biggest mistakes that people often make when trying to lose weight is to restrict their calorie intake.

While this can be beneficial in helping you lose those extra pounds, doing it too frequently or severely can cause more harm than good. Furthermore, it can even lead to other issues that can affect your overall health.

We are here to show you some of the potentially harmful side effects that can occur if you partake in calorie restriction as part of your weight loss plan. Read on for more information to help you determine what amount of restriction is safe for your body.

Why Do We Need Calories?

The definition of calorie is the amount of energy needed to raise the temperature of water by 1o Celsius (1.8 o Fahrenheit). This amount of is equal to 4.1868 joules of energy.

Generally, calories are used as a unit of measurement for energy that we consume or use. Everything we do requires energy and nearly everything we eat for nourishment purposes also has energy in it. The food we choose at the grocery store all has a predetermined amount of calories in it that we would extract from it if we were to digest it.

Specifically, there are three different processes that our body goes through which require calories for continuous function. They are:


While we get most of our calories from food when we digest it, the actual process of digestion requires calories in order to successfully digest and convert the food into calories.

Physical Activity

You guessed it, any physical activity you partake in require calories. Walking, running, lifting, standing, sitting down, everything you do that requires the use of your muscles will use calories. Obviously, some tasks will require more calories than others.

Basal Metabolic Rate (BMR)

Your basic functions like keeping your heart beating and the rest of your organs working as intended require calories. All automatic functions that you don’t think about require energy.

Ideally, if you consume more calories than your body needs for all three of the above processes then you will gain weight. On the flip side, if you consume fewer calories than your body needs for those same functions, you should lose weight.

The problem is removing the calories in the right spot without affecting the above functions and possibly hurting your body’s standard functionality. The best way to shed weight still remains reducing your calorie intake, but you have to do it properly.

Restricting calories the wrong way can lead to some serious problems. Furthermore, it is even possible that improper calorie restriction can have the opposite effect on your body and lead to weight gain instead of weight loss. Let’s take a look at some of the possible negative effects of calorie restriction.

Slower Metabolism

One of the things that your body does if it experiences frequent calorie restrictions is slow down your metabolism to conserve energy. It’s sort of a defense mechanism. Your body goes into energy conservation mode and can decrease the amount of calories burned during calorie restriction periods by up to 25%.

The problem with your metabolism slowing down is that it can persist even after you have started eating normally. This means that all those calories that you are getting back into your body after you have slowed down your metabolism often get converted into fat instead of being burned by you for energy. This is possibly the reason why people who go onto a calorie restricting diet usually end up gaining most of their weight back after they switch to their regular diet. This happens to about 80% of people who restrict their calories.

The other problem of calorie restriction is that this metabolic slowdown usually affects your muscles first, causing muscle mass loss. This usually happens if the calorie restriction diet isn’t built properly and there is a lack of protein in the diet and there isn’t enough physical activity mixed in to help sustain your muscle growth.

The best way to avoid metabolic slowdowns is by making sure that you never restrict more calories than your body needs to keep your basal metabolic rate at its proper level. When your body senses that the amount of calories you are receiving isn’t enough to sustain proper BMR, this is exactly when your metabolism slows down.

We strongly suggest increasing your protein intake whenever you decide to go onto a calorie restriction diet. This will ensure you are getting enough fuel for proper muscle synthesis. We also strongly suggest pairing your restriction diet with muscle resistance training to keep your muscle growth active and prevent muscle mass loss.

Weakened Bones

This is something that many people overlook. Just like our muscles, our bones need plenty of nutrients and energy to function properly and stay strong. But the major reason why calorie restriction can do major damage on your bones is hormonal imbalances.

Often, calorie restrictions can lead to a decrease of estrogen and testosterone. The side effects of dropped levels of both of these hormones include a decrease in bone formation and accelerated bone breakdown. Both of these effects combined together lead to much weaker bones.

Additionally, calorie restrictions can also lead to an increased level of stress hormones. Stress hormone levels also have an effect on our bone strength.

Overall, this bone strength reduction can lead to serious problems and even frequent fractures. This can be a nightmare, especially if you are planning on spending a lot of time at the gym and putting more stress onto your body and your bone structure.

Reduced Immunity

Reducing the amount of calories you consume can also lead to frequent infection and make you more susceptible to illnesses.

Generally, this applies to viruses like the common cold and those that are often prominent when combined with physical activity. Researchers have done studies on athletes who were restricting their calorie intake in an attempt to lose weight before their competition started. The results were that these athletes were twice as likely to develop infections and become sick while observing this calorie restriction.

The same effects haven’t been observed on individuals who weren’t taking part in physical activities while reducing their calorie intake and more research needs to be done to determine the full effects of calorie restrictions.

Nutrient Deficiency

Another huge problem with calorie intake reduction is that it can lead to a reduction in the nutrients that you need to function properly and maintain proper health levels. Furthermore, it can lead to sever fatigue.

Some nutrients such as iron and vitamin B12 can lead to fatigue and even anemia if you don’t have the proper supply of these nutrients. The same can be said about carbohydrates. If your calorie restriction diet doesn’t include enough carbs in it, the result may be higher than normal fatigue levels in some individuals. Although, other studies have shown that reducing carb intake during calorie restrictive dieting has shown to also reduce fatigue levels, so it seems that carb consumption can have a different effect for each individual.

There are other nutrients that can become limited if you partake in a calorie restricted diet that can lead to other issues. Protein is one of them. The biggest issue with reduced protein intake is increased muscle loss which can lead to other problems. Calcium deficiency can also occur if you restrict your calories.

This can lead to reduced bone strength and increased risk of fractures. Permanent eye damage and a weaker immune system can be a direct side effect if you don’t get enough vitamin B in your system, which may happen if you restrict your calories. Increased muscle cramps and an irregular heartbeat can occur if you don’t get enough magnesium in your system.

As you can tell, there are plenty of possible negative side effects that can occur if you aren’t getting the right nutrients during your restrictive dieting. You have to make sure that you are receiving plenty of vitamins, nutrients, and minerals whenever you decide to reduce your calorie intake.

Calorie Restriction Side Effects Final Words

Before reducing your calorie intake, you first have to determine the optimal amount of calories you need. There are many factors that can change this number such as your age, sex, height, weight, and activity levels. Your best bet is to determine how many calories you need for proper BMR and never go below this number.

There are estimation calculators that you can use online, but we strongly suggest talking to your doctor or nutritionist to determine the perfect calories your body needs to maintain good BMR.

Losing weight is a process that takes time. It is always best to focus on diets which are designed for long term duration. Diets that request high calorie restrictions usually don’t work well because of the problems and issue that they can bring to the table.

Patience is key when it comes to losing weight, and restricting your calorie intake lightly over a long period of time will be much more beneficial in the long run. Plus, it will also reduce the risk of any of the above mentioned side effects occurring. Take your time and be persistent, this is the only way to successfully shed the weight and keep it off.

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