I also do sit-ups, but I'm not fat and have no meat in my abdomen, so sometimes I do it when I don't have time. However, if you want to lose weight, you must stick to it and it will be effective. Otherwise, any effective way to lose weight is useless, because nothing is effective at once. You can't just rely on exercise, but also pay attention to your diet. When you are abroad, foreigners eat a lot. Weight gain is inevitable. You can eat more fruits and vegetables and less meat and milk. Don't sit down immediately after dinner, stand for a while, or take a walk near home, which will help digestion. Also, it is best not to eat for 4 hours before going to bed, 1 hour and drink less water. I hope it helps you!