Weight loss is not about the exercises you do. It's 100% about the food you eat. Whatever exercise you choose, be it beginner's yoga or Insanity, you need to adjust your nutrition to create the calorie deficits that will help you lose weight.
Contrary to popular belief, exercise is not how you lose weight. ;) It helps, and it's absolutely critical for healthy living, but real weight loss happens in the kitchen. If you're not already tracking your food and weighing and measuring what you eat, it's time to start!