One of the things that I have learned as an athlete is the important role of basal metabolism in achieving our body goals. Basal metabolism is the minimum energy consumption that the body requires to live when it is at rest. This minimum consumption varies from person to person.
Although the exact number of calories that muscle burns relative to fat varies, fat is not very metabolically active, which means that very few calories are needed to keep it. Specifically, you need between one and two calories per day for every half pound of fat. Unlike muscle, which is believed to burn between five and thirteen calories a day for every half kilo.
Basically, muscle burns more calories than fat.

Body composition
A person with a given weight and higher lean mass (which includes connective tissues, muscles and bones) burns more calories than a person with a lower lean mass. Think of an athlete and a non-athlete with a similar weight: the one with a more muscular body has a faster metabolism.
In other words, a lean, muscular person weighing 165 pounds has a healthy amount of lean mass and a relatively “fast” metabolism; however, another 165-pound person who has much less lean mass and more fat, so their metabolism will be “slower”.
So the more muscle mass we have, the more calories we consume per day. This is why it is possible to speed up our metabolism.
What is the metabolism?
Metabolism is the set of chemical reactions that take place in the cells of the body to convert food into energy. Our body needs this energy for everything we do, from moving to thinking to growing.
The metabolic rate is the rate at which the body uses available energy (or burns calories). In general, the more muscle and less fat your body has, the faster your metabolic rate becomes. This varies according to sex (male, female) according to genetic inheritance and your lifestyle (diet and physical activity), so it is important to know that you can make changes to achieve a higher metabolic rate.
When the metabolism is fast, fat does not tend to be stored in the body and the person does not gain weight. When it is slow, fat is stored and the person becomes fat.
How can you speed up your metabolism naturally?
Drink More Water
To burn calories the body needs water. The metabolism slows down when we are dehydrated.

Eat Several Small Meals a Day
Eat several small meals per day, instead of spaced and abundant meals. Eat no less than 1,200 calories a day or your metabolic rate will slow down. Eat before you’re hungry.

Season with Spicy ingredients
Red or green hot pepper temporarily speeds up the metabolic rate.

Coffee
For a short time it accelerates the metabolic rate, it must be taken in moderation.

Green Tea
Increases the metabolic rate for a couple of hours. Drinking two to four cups a day causes the body to burn 17% more calories than normal.

Protein
The body burns more calories when digesting protein than when digesting carbohydrates or fat. Eat foods rich in protein. You can check my 9 Food to Change Your Body article.

Weight Lifting Exercises
Doing a weight routine at the gym will increase your muscle mass. The metabolic rate is higher in people with more muscle mass.

Although it is true that genes, gender and age have great importance in the metabolic rate and it is not possible for you to change these factors, you can influence it by putting into practice the previous tips.
And, above all, be active, exercise and keep the motivation!