Nature Crave Keto Lean Meats and Fish: More calories are burned when digesting protein, so opt for turkey or fish, especially tuna or salmon. Avocados are another great source of fiber and make great additions in a salad. Cutting down on fat, including butter, oils, salad dressing and mayonnaise leads to a thinner you. A proper fast weight loss diet program teaches people how they can create scrumptious snacks and meals. Now imagine if you could transplant such a lifestyle and diet to the modern world, and add today’s medicine, and lack of dying from woolly mammoth attacks, you would have the ultimate weight loss program.