Of course, exercise is the most effective way to lose weight. If you stick to an exercise plan for your stomach, it will be effective in one month. Do it for at least half an hour every day, and the muscles in your stomach will be exercised. Sit-ups, running, as for whitening, you said it was dark around the nose and mouth. Have you ever had acne before? I suggest you choose Nivea's skin care products for maintenance, and then go to the store to buy a bag of facial mask (not the one you made yourself), usually 1.5 or 2 yuan a bag, and apply it every day for half a month. Be careful not to expose yourself to the sun, or even the best mask will be useless.