Sir.you should understand that weight reduction should always be proportion to their respective height and age.And most importantly with age most of them will have co-morbidities like diabetes, hypertension etc so the diet plan should be according their health needs and weight reduction should always be gradual, my advices are- you should avoid eating oily and spicy foods, avoid sugary substances like sweets and diary products since it contributes too much of calories. If you are a non vegetarian skip consuming meat like mutton instead you can prefer skinned out chicken 1-2 pieces which should be a cooked variety not a fried type and it should be only once a week or you can have fish curry not fish fry, since fried food substances have lot of oil which will cause gastritis.prefer fresh fruits like pears,apples, citrus fruits,jamon, berries like blueberries,raspberries and include fresh vegetables in the form of salads.have fresh sprouts daily in the morning. Prefer daily egg white and a glass of milk in your diet. Try to include brown rice, oats into your diet.prefer olive oil or if not available then sunflower oil for cooking. Avoid cocunut in your cooking since it is rich in cholesterol.prefer buttermilk and ragi gunji than coffee and tea .prefer home cooked meals. Drink plenty of water to stay hydrated. Do daily morning cycling for 30-40mins. Do daily morning meditation and yoga. In the evening do brisk walking for 30-40 mins.if you are not satisfied kindly consult a dietician.