Weight loss can significantly help manage diabetes. Emphasise doing regular exercise and following a healthy diet to lose weight. Few methods that can help in weight loss are:

• Physical exercise

• Cycling
• Yoga
• Brisk walking
• Jogging

• Healthy and balanced diet

• Avoid junk/oily food as much as possible.
• Count your daily calorie intake.
• Divide your total calories into six small meals instead of three large meals.
• Try to stay away from excess carbohydrates.
• Include fibre-rich food items in your diet.
• Stay hydrated.

Leading a healthy lifestyle along with medications would help your friend manage his blood sugar levels.

Read more about glycemic index.