hi neha welcome,
A slow metabolism
is rarely the cause of excess weight gain. Although your metabolism influences your body's basic energy needs, it's your food and beverage intake and your physical activity that ultimately determine how much you weigh.
To lose weight, then, you need to create an energy deficit by eating fewer calories, increasing the number of calories you burn through physical activity, or both.
TO INCREASE YOUR METABOLISM,
1-Exercise is widely regarded as the most prominent way to increase metabolism and certainly the most natural of ways to increase metabolism
2-By measuring your calorie intake you can also control the amount of body mass you are likely to gain ,so cutting out any unnecessary calories, as you would in any balanced diet, will be an effective way to increase your metabolism as intended.