Building muscles without gaining fat mass is not the easiest task in bodybuilding, but it can definitely be done.

There are several factors that can influence this process:

Level of training

Diet

Cardio

Age

Level of training

People that are beginners in training usually have the capacity of building easier muscles than accumulating fat mass. This is due to the fact that when you are a beginner your body needs to do many adaptations in order for it to face the future trainings. So it will consume a lot of energy do these adaptations.

These adaptations are usually things like: increasing muscle size, strengthening tendons, strengthening ligaments, strengthening bones and improving some functions. All these things will need calories that the body will take from the fat deposits.

On the other hand a person that is advanced in training, for example 3-4 years, usually will build muscle mass and fat tissue at the same rate, if the diet and training are not adjusted accordingly.

Calories

In order for someone to build muscles without gaining fat is important to know his maintenance calories.

The maintenance calories are basically the amount of calories that someone can eat without gaining weight. A method through which you can find your maintenance calories is to eat every day the same amount of calories and see if you gain, lose or stall in weight. If you gain weight you reduce them with 200-500 calories, if you lose weight you have to increase them with 200-500, but if you stop you found your maintenance weight.

Keep in mind that you have to eat the same amount of calories for 1 week to draw conclusions.

Diet composition

To build muscles without fat gains you also have to have a diet that is based on foods rich in proteins and low in other macronutrients ..

The diet composition can look something like this: 25-30% proteins, 20-30 carbohydrates and the rest percents fats.

A trick which you can do to keep fat accumulating away, is to eat carbohydrates like in the above example in the training days and in the off days to reduce them to about 100-150 grams max per day.

Cardio

Cardio is a tool that can help you burn some extra calories in order for you to reach your maintenance levels. Depending how you use it, cardio can have a good or a bad impact on your muscle gains.

The best thing to do if you need to burn some calories is to do low intensity cardio, mainly a fast walk.

The duration of cardio will depend of your needs, for example with 10 minutes of low intensity cardio you can burn around 100 calories. So, if you need to burn 500 calories in a day, you will have to do around 40-50 minutes of cardio.

Usually, if you do the cardio on a treadmill it will show you how much calories your burned.

Age

This last factor can have an important impact when it comes to building muscles without gaining fat, mainly because with the passing of years the body's metabolism decreases in its activity, usually with 10% at every 10 years.

A younger person will build lean muscles easier, than a person that let's say is 40 years old. At this age you must be very careful about every factor that can influence fat gain.

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