The Energy Balance Equation = Calories in V Calories Out
You burn a certain amount of calories just existing (Your BMR)
You burn some calories depending on your activity levels through the day
This combined is your Total Daily Energy Expenditure (TDEE)
This is your Calories Out
Everything you eat has a calorific value, everything you eat in a day gives you Calories In.
If Calories In and Calories Out are equal consistently you will maintain your current weight
If Calories In is more than Calories Out consistently (creating a surplus) you will gain weight
If Calories In is less than Calories Out consistently you will lose weight
Calories In being less than Calories out is the definition of a Calories Deficit
Consistently is the key word, one day in surplus or deficit will not make a difference
If you want to lose weight and are not you need to review Calories In
You could keep Calories In the same and look at increasing Calories Out but this may be difficult to do depending on your current activity levels
It may be ideal to look at both reducing Calories In a little and increasing Calories Out a little
Calories are calories regardless of whether they come from fat, carbs or protein. Different amounts of calories make up different foods but when it comes to being in a calorie deficit how those calories are made up is not relevant