In this case, you should see a doctor in gastroenterology as soon as possible. There are many reasons for losing weight, which need to be investigated clearly. Diabetes may lead to weight loss, intestinal syndrome may also lead to weight loss, lack of sleep, constipation and so on. I've also looked into this problem, and now I'm beginning to gain weight. Pay attention to physical exercise and supplement protein.

Good health!

I read a lot of answers downstairs, all of which emphasized eating and not seeing a doctor. This is wrong, now is the era of digital medical care, health should speak with data)