Starting in earnest

Welcome. Sounds like you've got some serious motivation. You don't want to restrict your diet a great deal, because that can lead to burnouts and binges. Overly restricting yourself has the potential to make you miserable and, therefore, more likely to abandon your progress after a while (I'm speaking from experience).

Did your doctor specifically tell you to cut out 100% of grains and sugar? If not, there's no reason to limit your diet so drastically. Losing weight comes down to a calorie deficit, regardless of what you eat (including carbs). Some people prefer a low-carb way of eating because it allows them to stay fuller for longer, but fat loss is only about eating fewer calories than you burn. That's it. No food is “good” or “bad” for weight loss as long as you’re in a calorie deficit. You could lose weight eating only buttered donuts as long as you burn more calories than you consume. Unfortunately, because buttered donuts are very calorie-dense (a lot of calories for a small amount of food), you’d be pretty hungry often. Eating foods lower in calories allows you to eat more, so you stay fuller for longer. Eating only buttered donuts would also adversely affect your overall health after a while (not getting enough vitamins, minerals, fiber, etc.), but weight loss is all about calories – Eat fewer than you burn, in whatever form suits you, and you’ll lose weight.

I tend to do better with a higher carb diet (I don't get as hungry throughout the day), but many other people prefer a low-carb, high-protein/fat diet to help with their satiety, but that's all it's about - feeling full so you don't eat above your calorie limit.

Here's a great post to help you get started: https://community.myfitnesspal.com/en/discussion/1080242/a-guide-to-get-you-started-on-your-path-to-sexypants/p1

Good luck! A lot of great resources and people here to help you along the way