The first step is to find out how quickly the extra pounds were gained. Rapid weight gain can indicate a variety of medical conditions and should be checked by a doctor.
If everything is in order with the first item, then we check if you have a real "advantage". That is, calculate your BMI. for example that http://www.bmi.name/ru/
If in point 2 you found out that you really have an extra 10 km, then "just" give up sweet and fatty foods. For example burgers, pizzas, sugary drinks, etc.
Sports when losing weight is just an addition to proper nutrition.
If you want to lose weight, start counting calories.
Not worth it. You need to move more and eat more restrained. Walk a kilometer or two more a day (you can get out of the transport at a stop or two earlier, and if you walk close, then walk not in a straight line, but make a circle), give up the elevators or go up the stairs at least five floors ( but this is if there is such an opportunity), do not sit constantly, if possible, get up, twist, bend over, warm up. Morning exercises are a pleasure for a connoisseur, but also useful. In your diet, limit fried, fatty, rich, fresh bread, sweet pastries. And that's enough to try how the body will behave.
If in a couple of months the weight does not start to return to normal, then figs with him. But if it continues to increase, then it makes sense to go to the doctor and find out the reasons for the appearance of excess weight. And even then, if there are no sores, you can go to sports facilities. Although, in my purely personal opinion, this is money down the drain. The same doctor who will diagnose, he will also prescribe a diet and exercise that will be easier, faster, more useful and free.