Its easiest to stop buying the things that are bad for you, simply ban the following foods from your home, and avoid when eating out.
Fizzy drinks, sports drinks, any with any sugar in.
(Drink only tea and coffee (without sugar )and water.)
Cakes, pastries, sweets,, chocolates, biscuits, ice cream.Energy bars, anything processed into a 'bar'
(Replace with nuts, oatcakes, fruit in moderation.)
Takeaways.
Tinned food with added sugar, ie baked beans, sauces, custard, etc. check the ingredients.
Replace with meals consisting of; meat, grilled, baked or roasted.
with vegetables, stir fried, roasted or steamed, as many as you like.
Omelets with chicken, ham, tomatoes, onion, sweet peppers etc.
Casseroles with meat, vegetables, (no potato) serve with brown rice, lentils..
Curries.
If you stick to mostly lean meat and fish with tons of vegetables, ( keep potato and parsnips to a minimum or cut them out entirely) the weight will drop off you without exercise.
It is all about replacing each thing you eat with a better option, ie breakfast, replace sugary cereals, with bacon and poached eggs, or porridge and blueberries.
Replace a chocolate or cake snack with avocado on Ryvita, or almonds and an apple.
Replace a sandwich , crisps and fizzy drink lunch with, cold chicken, crudite, and a small portion of brown rice.
Replace burger and chips with, a grilled steak or fish, and a ton or roasted vegetables.
Emergency snacking on bicuits with some very dark chocolate.
Don't count calories, just stick to three rules.
No sugar
limited carbs
modest portions.
Walking briskly is good until you lose some weight, then l agree with other posters find somethimng you love to do, dance, gym, jog.
But remember it is always 90% food, and 10% exercise.
Good luck for a healthy 2020.