CrossFit if you have a powerlifting / Olympic lifting / athletic background. You will need to simultaneously be exhausted and perform technical lifts properly to prevent injury.
Do orange theory fitness if your athletic background is limited to a joystick.
Talking about diet - never, ever, ever enter the middle of a grocery store. 100% of the shopping should occur in the outer edge or first/last aisle. Fresh produce, meats from the deli, frozen section. Don’t eat American breads, processed garbage in the middle of the store, sugars in boxes, and food that doesn’t look like an animal muscle or actual leaf/stalk/fruit/vegetable of a plant
I lost ~80 pounds by doing diet + high intensity exercise. I had always been a primarily year round athlete since about 3. It’s extremely true that diet has the greater impact. Once I jump started my metabolism with CrossFit for about 2 years, I stopped and continued to lose weight for 4 years with diet.
Try to do something you can sustain. If you lose the weight too fast you lose muscle mass as well and if you gain the weight back you will be more “fatty” and it will be harder to lose. These really low carb diets are good if that’s what you want to do for ever. If not, eat better overall, have a cheat day once per week (don’t go crazy but eat that pizza if you want etc) and exercise at least 4-5 times per week and make sure to includes weights.
First, figure out what your maintenance caloric intake is (the amount of calories per day that if you ate you would stay the same weight, hint it’s very likely not the standard 2,000 that everything is based off). From there, figure out the best way for you to get your net intake below that amount (could be eating less calories, or burning more).