Three groups of stuff that your body burns to free up energy for your body to use:
1. proteins
2. fats
3. carbohydrates
When you digest your body breaks down these molecules, and as the chemical bonds break down that frees up the energy.
Typically:
1g protein = 4kcal energy
1g carbs = 4kcal energy
1g fats = 8kcal of energy
This suggest drop fats.
HOWEVER.
The body needs protein and fats for other stuff. Fats are very important for fat soluble vitamins: A, D, E, and K. Without these your body will suffer deficiency, and without fat you won't get these.
So drop carbohydrates instead.
As far as I know no vital processes need carbs, so this one is relatively safe to cut back on. But Bernd will correct me if I'm wrong.
You consume carbohydrates typically in the form of starch and a variety of sugars. So pasta, potato, rice, sweets are the chief targets to reduce in your diet.
However.
You don't really need that much fat, just some. And if you drop stuff like ice cream, that has lotsa fats too.
If you stick to meat (a variety of meat, from fish to beef), eggs, diary products, and various nuts you should get the fats your body needs.
Quick word about proteins. There are over 20 (21 or 23 or something like that) amino acids which we call collectively proteins. 9 of these are essential for human beans, which means the human body can't produce/syntheses them from other chemical building blocks, so we need to take them via food. Typically meat, eggs, and diary products contain them all 21-23, they give "full protein". Ofc a combination of various other foodstuff can cover it, such as rice combined with beans, but really have to know what foodstuff contains which amino acids which is a stupid thing to follow - just eat meat (and eggs and diary products).