Keto. Cut out all carbs, less than 50g per day. Eat mainly veggies and fish and chicken, occasionally red meat. Don’t pig out on bacon and cheese either, go for walnuts and avocado and similar for unsaturated fats. No sugar at all. No beer. Only healthy fats. I lost 40 lbs in 6 months. Then switch to a low carb diet afterward and exercise more and watch your calorie intake to keep the weight off. Do NOT do keto for long term (over 1 year) unless your doctor says it’s okay.

Edit: here’s some good meal ideas

Breakfast: plain Greek yogurt with raspberries, or a hard boiled egg and some walnuts or almonds. If you have time at home, cook a few eggs and put them over a sautéed veggie hash

Lunch: Romaine lettuce wraps with turkey, avocado, and light cheddar cheese and light mayo. Chicken stuffed bell peppers is pretty amazing too. Or you can get cauliflower crusts and make a proper pizza with your favorite non-carb toppings(which most aren’t)

Dinner: cauliflower fried rice with your favorite protein. Baked salmon and Brussels. Philly cheese steak lettuce wraps. Spaghetti squash is a great replacement for lighter noodles. Spiralizing zucchini is great too

Snacks: have fresh almonds and walnuts around. Try tossing them in light olive oil and throw some spices on them! String cheese, hard boiled eggs, and avocados are awesome to have around if you feel snacky.