How Can Stomach Sagging Be Reduced?

Tightening the Tummy Iam 51 years old and weigh 77kgs.Recently I have lost 6 kgs and my weight stabilized at 77 kgs which works out to a BMI of 25 as my height is 5’10”.I maintain regular exercise -aerobics,strength training,abdominal exercises and evening walk of 4 kms.I eat selectively without oil,less Non veg,less sweets,more fruit and water ,steamed vegetables,sprouts,Almonds(4 nos) and 1 egg white.When I go to gym I take whey protein of 30 gms. My problem is with my stomach muscles.Inspite of my exercise and moderate food habits I have a stomach of 36 inches.When I sit down I have to adjust my belt by changing the hole.When I wear underwear I feel very tight in abdominal area.Thats why I stopped wearing underwaear except when I exercise. I consulted a specialist who is into weight loss surgery like gastric band and sleeve who initially suggested to go for liposuction.When I requested for a non surgical solution he offered me a complimentary session on Radio frequency Tripolar machine.He promised that I will loose 2 inches over 6 sittings.For each sitting there should be a gap of 2 weeks.He says the skin also will be tightened apart from fat reduction in the tissues.I have also read that this can be done by Ultrasound Lipolysis and Zerona laser treatments. Please suggest me which is ideal for reducing my stomach sag.