The answers given are all excellent. Perhaps the most important thing to keep in mind are the ADA’s recommendations. No special short-term diet plan. Just keep to the research supported suggestions of about 60% carbs (less than 15% simple sugars), 15-20% protein and 15-20% fats (less than 20% saturated).
And add to that a vigorous exercise program (30-60 min/day, 3-5 days per week). that includes cardio, strength and stretching. Vigorous is the key word.